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1.  Mutually exclusive groups of bronchitics and non-bronchitics in males 
Seven mutually exclusive groups of non-bronchitics and chronic bronchitics are derived from 10,816 steel workers questioned and examined at Port Talbot. These groups are based on various combinations of responses to the Medical Research Council questionnaire on cough, phlegm, dyspnoea, increased cough and phlegm, and chest illness. The groups are formed on defined criteria of (1) a reasonable number of men in each group; (2) impairment of lung function (FEV1) related to the severity of chronic bronchitis symptoms; and (3) impairment of lung function from certain other diseases.
The ideal group of non-bronchitics (NB 0) answered `no' to every symptomatology question (46·4%). Non-bronchitics grade 1 (NB 1) were either symptom-free or had only occasional cough and phlegm with either or both increased cough and phlegm and chest illness (24·2%). Non-bronchitics grade 2 (NB 2) complained of dyspnoea in the absence of persistent cough and phlegm (4·3%). Chronic bronchitics grade 1 (CB 1) had persistent cough and phlegm in the absence of any other complaint (11·3%). Chronic bronchitics grade 2 (CB 2) had the additional impairment of increased cough and phlegm and/or chest illness (8·1%). Grade 3 (CB 3) complained of dyspnoea with or without increased cough and phlegm (2·5%). Grade 4 (CB 4) had both dyspnoea and chest illness (3·2%).
Lung function (FEV1) in three of the groups of chronic bronchitics (CB 1, CB 2, CB 3: 21·9%) was no worse than in the two groups of non-bronchitics with complaints of other respiratory disorders (NB 1, NB 2: 28·6%). An overall comparison on a binary division between non-bronchitics and bronchitics hides the severity of some of the bronchitic groups. For this reason it is recommended that epidemiological studies of chronic bronchitis should separate the suggested grades of bronchitics (CB 1, 2, 3, and 4) and compare them with the ideal group of non-bronchitics (NB 0: 46·4%) which has the lowest prevalence of heart trouble and asthma and those who have had pneumonia.
PMCID: PMC478855  PMID: 4414747
2.  The impact of quitting smoking on symptoms of chronic bronchitis: results of the Scottish Heart Health Study. 
Thorax  1991;46(2):112-116.
Scotland has high rates of death from diseases of the respiratory system and high rates of smoking, especially among women. Data on self reported smoking and prevalence of chronic cough and chronic phlegm among 10,359 men and women aged 40-59 years were obtained from the Scottish Heart Health Study. Overall, current cigarette smokers had rates of chronic cough and chronic phlegm four to five times those of never smokers after standardisation for age (32.3% v 6.5% for men and 24% v 5.5% for women for chronic cough; 31% v 8.3% for men and 21% v 5.5% for women for chronic phlegm). Ex-smokers' symptom rates were a little above those of never smokers and were significant for chronic cough among women and chronic phlegm among men. Men had higher symptom rates than women and this was true for smokers, ex-smokers, and never smokers. The higher rates among men could not be explained by higher cotinine concentrations. Tests to detect "deceivers" among ex-smokers and never smokers using biochemical validation suggested that 87 (1.5%) respondents were in fact smoking; they were excluded from analyses. There were substantially lower rates of chronic cough and chronic phlegm within a year of stopping smoking, and two to four years after stopping 89-99% of the difference between current smokers and never smokers was accounted for (99% and 93% for men and women with chronic cough, 96% and 89% for men and women with chronic phlegm). Even 10 years after stopping, rates of symptoms among ex-smokers remained a little above those of never smokers (except for women with chronic phlegm), though these differences were not statistically significant. Former heavy smokers continued to have rates of chronic cough and chronic phlegm that were higher than those of former light and moderate smokers (though not significantly so). These are cross sectional data, but they emphasise the importance for chronic bronchitis symptoms of giving up cigarette smoking, though the amount previously smoked continues to exert a small influence.
PMCID: PMC462964  PMID: 2014491
3.  RESPIRATORY SYMPTOMS AND SMOKING HABITS OF SENIOR INDUSTRIAL STAFF 
The prevalence of respiratory symptoms and the smoking habits of 224 industrial `executives' aged 30 to 69 years in Social Classes I and II were ascertained by means of the Medical Research Council's questionnaire on respiratory symptoms; 31% had persistent cough, 25% had persistent phlegm, and 21% were short of breath on hurrying or going up a hill; 9% had had one or more chest illnesses in the past three years lasting for about a week, and 4% had `chronic bronchitis'—defined as persistent phlegm and one or more chest illnesses in the past three years; 67% were smokers, 21% smoking more than 25 cigarettes (or equivalent tobacco) per day; another 20% had stopped smoking. The prevalence of cough, phlegm, and breathlessness was closely related to smoking habit.
Data for those aged 40 to 59 years are compared with that obtained from London Transport Board workers and a sample of the population studied by the College of General Practitioners. The latter was further analysed and suggests that the prevalence of cough and phlegm is more closely related to the amount smoked than to social class. The prevalence of chest illness is probably more closely related to social class and less to the amount smoked. It is suggested that, although smoking may initiate irritative respiratory symptoms, the precursors of bronchitis, additional factors are important in causing progression to disabling or fatal chronic bronchitis.
PMCID: PMC1008262  PMID: 14278803
4.  Respiratory and allergic symptoms in wool textile workers. 
An epidemiological study of 2153 workers in 15 West Yorkshire wool textile mills was conducted to determine relations between respiratory symptoms and exposure to inspirable wool mill dust. A questionnaire designed to elicit all the common respiratory symptoms was developed and tested, and administered to all workers willing to participate (85%). It was translated and administered in Urdu for the 385 workers from Pakistan whose English was not fluent. Symptoms investigated included cough and phlegm, wheezing and chest tightness, breathlessness and its variability, rhinitis, conjunctivitis, chills, nosebleeds, and chest illnesses. Additional questions were asked, where appropriate, about the times of day, days of the week, seasons, and places that the symptoms were worse or better than normal. An environmental survey was carried out at each mill, which included 629 measurements of inspirable dust, enabling estimates to be made of the airborne concentrations of inspirable dust usually experienced by each member of the workforce under current conditions. Overall symptom prevalences were: persistent cough and phlegm, 9%; wheeze, 31%; breathlessness on walking with others on level ground, 10%; persistent rhinitis, 18%; persistent conjunctivitis, 10%; persistent chills, 2%; ten or more nosebleeds a year, 2%; and three or more chest illnesses in past three years, 5%. After allowing for the effects of age, sex, smoking habit, and ethnic group, cough and phlegm, wheeze, breathlessness, rhinitis, conjunctivitis, and nosebleeds were found to be more frequent in those exposed to higher than to lower concentrations of dust. In some experiencing high concentrations (blenders and carpet yarn backwinders) cough and phlegm, wheeze, rhinitis, and conjunctivitis were related to the years worked in such jobs. Relative risks of each symptom in relation to inspirable dust concentrations were calculated by means of a logistic regression analysis. At concentrations of 10 mg/m3, the current United Kingdom standard for nuisance dusts, the risk of cough and phlegm relative to that of an unexposed worker was 1.37, that of wheeze 1.40, breathlessness 1.48, rhinitis 1.24, and conjunctivitis 1.70. Since some of these symptoms may be associated with functional impairment of the lungs, further studies of selected workers are being carried out to estimate the functional effects of exposure to dust in wool textile mills.
PMCID: PMC1009690  PMID: 3264511
5.  Respiratory symptoms as predictors of 27 year mortality in a representative sample of British adults. 
BMJ : British Medical Journal  1989;299(6695):357-361.
OBJECTIVE--To examine associations between reported respiratory symptoms (as elicited by questionnaire) and subsequent mortality. DESIGN--Prospective cohort study. SETTING--92 General practices in Great Britain. PARTICIPANTS--A nationally representative sample of 1532 British men and women aged between 40 and 64. MAIN OUTCOME MEASURES--Mortality from all causes, cardiovascular disease, lung cancer, and chronic bronchitis. RESULTS--Subjects were interviewed in 1958 regarding various respiratory symptoms (including cough, phlegm, breathlessness, and wheeze) by using a questionnaire which formed the basis of the Medical Research Council's questionnaire on respiratory symptoms. By the end of 1985, 889 deaths had been reported, including 51 in men due to chronic bronchitis. After adjustment for differences in age and smoking habits death rates from chronic bronchitis in men who reported symptoms were greater than those in men who did not for each of the symptoms examined. The adjusted mortality ratios were 3.4 (95% confidence interval 1.8 to 6.5) for morning cough, 3.7 (2.0 to 6.9) for morning phlegm, 6.4 (3.0 to 13.8) for breathlessness when walking on the level, and 10.5 (4.4 to 24.6) for wheeze most days or nights. Mortality ratios were also significantly raised for four episodic symptoms not usually included in more recent respiratory symptom questionnaires--namely, occasional wheeze (mortality ratio 6.0; 95% confidence interval, 2.4 to 15.1), weather affects chest (5.7; 3.1 to 10.3), breathing different in summer (4.9; 2.8 to 8.6), and cold usually goes to chest (3.7; 2.0 to 6.8). The excess mortality associated with these symptoms remained significant after further adjustment for breathlessness or phlegm. Ratios for all cause mortality in men and women were also significantly raised for most respiratory symptoms, death rates being some 20-50% higher in people reporting symptoms after adjustment for age, sex, and smoking. Breathlessness was the only symptom significantly associated with excess mortality from cardiovascular disease (mortality ratio 1.4 (95% confidence interval 1.0 to 1.9) for breathlessness when walking on the level). Ratios were generally around unity and not significant for mortality due to lung cancer. CONCLUSIONS--The results suggest that episodic symptoms, which often do not appear in standard respiratory questionnaires, predict subsequent mortality from chronic obstructive airways disease. This supports the hypothesis that reversible airflow obstruction may be a precursor of progressive and irreversible decline in ventilatory function.
PMCID: PMC1837252  PMID: 2506967
6.  Incidence and prognosis of asthma and wheezing illness from early childhood to age 33 in a national British cohort. 
BMJ : British Medical Journal  1996;312(7040):1195-1199.
OBJECTIVE--To describe the incidence and prognosis of wheezing illness from birth to age 33 and the relation of incidence to perinatal, medical, social, environmental, and lifestyle factors. DESIGN--Prospective longitudinal study. SETTING--England, Scotland and Wales. SUBJECTS--18,559 people born on 3-9 March 1958. 5801 (31%) contributed information at ages 7, 11, 16, 23, and 33 years. Attrition bias was evaluated using information on 14, 571 (79%) subjects. MAIN OUTCOME MEASURE--History of asthma, wheezy bronchitis, or wheezing obtained from interview with subjects' parents at ages 7, 11, and 16 and reported at interview by subjects at ages 23 and 33. RESULTS--The cumulative incidence of wheezing illness was 18% by age 7, 24% by age 16, and 43% by age 33. Incidence during childhood was strongly and independently associated with pneumonia, hay fever, and eczema. There were weaker independent associations with male sex, third trimester antepartum haemorrhage, whooping cough, recurrent abdominal pain, and migraine. Incidence from age 17 to 33 was associated strongly with active cigarette smoking and a history of hay fever. There were weaker independent associations with female sex, maternal albuminuria during pregnancy, and histories of eczema and migraine. Maternal smoking during pregnancy was weakly and inconsistently related to childhood wheezing but was a stronger and significant independent predictor of incidence after age 16. Among 880 subjects who developed asthma or wheezy bronchitis from birth to age 7, 50% had attacks in the previous year at age 7; 18% at 11, 10% at 16, 10% at 23, and 27% at 33. Relapse at 33 after prolonged remission of childhood wheezing was more common among current smokers and atopic subjects. CONCLUSION--Atopy and active cigarette smoking are major influences on the incidence and recurrence of wheezing during adulthood.
PMCID: PMC2350975  PMID: 8634562
7.  Occupation and three-year incidence of respiratory symptoms and lung function decline: the ARIC Study 
Respiratory Research  2012;13(1):24.
Background
Specific occupations are associated with adverse respiratory health. Inhalation exposures encountered in these jobs may place workers at risk of new-onset respiratory disease.
Methods
We analyzed data from 8,967 participants from the Atherosclerosis Risk in Communities (ARIC) study, a longitudinal cohort study. Participants included in this analysis were free of chronic cough and phlegm, wheezing, asthma, chronic bronchitis, emphysema, and other chronic lung conditions at the baseline examination, when they were aged 45-64 years. Using data collected in the baseline and first follow-up examination, we evaluated associations between occupation and the three-year incidence of cough, phlegm, wheezing, and airway obstruction and changes in forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) measured by spirometry. All associations were adjusted for age, cigarettes per day, race, smoking status, and study center.
Results
During the approximately three-year follow-up, the percentage of participants developing chronic cough was 3%; chronic phlegm, 3%; wheezing, 3%; and airway obstruction, defined as FEV1 < lower limit of normal (LLN) and FEV1/FVC < LLN, 2%. The average annual declines in FEV1 and FVC were 56 mL and 66 mL, respectively, among men and 40 mL and 52 mL, respectively, among women. Relative to a referent category of managerial and administrative support occupations, elevated risks of new-onset chronic cough and chronic phlegm were observed for mechanics and repairers (chronic cough: RR: 1.81, 95% CI: 1.02, 3.21; chronic phlegm: RR: 2.10, 95% CI: 1.23, 3.57) and cleaning and building service workers (chronic cough: RR: 1.85, 95% CI: 1.01, 3.37; chronic phlegm: RR: 2.28, 95% CI: 1.27, 4.08). Despite the elevated risk of new-onset symptoms, employment in cleaning and building services was associated with attenuated lung function decline, particularly among men, who averaged annual declines in FEV1 and FVC of 14 mL and 23 mL, respectively, less than the declines observed in the referent population.
Conclusions
Employment in mechanic and repair jobs and cleaning and building service occupations are associated with increased incidence of respiratory symptoms. Specific occupations affect the respiratory health of adults without pre-existing respiratory health symptoms and conditions, though long-term health consequences of inhalation exposures in these jobs remain largely unexplored.
doi:10.1186/1465-9921-13-24
PMCID: PMC3352304  PMID: 22433119
ARIC study; epidemiology; occupation; respiratory tract disease
8.  Childhood exposure to environmental tobacco smoke and chronic respiratory symptoms in nonsmoking adults: The Singapore Chinese Health Study 
Thorax  2005;60(12):1052-1058.
Introduction
Childhood exposure to environmental tobacco smoke has been extensively associated with childhood respiratory illness; fewer data address adult effects.
Methods
We examined childhood environmental tobacco smoke exposure in relation to chronic cough, phlegm and asthma diagnosis among never smokers from a cohort of Singaporeans of Chinese ethnicity, aged 45–74 at enrollment from 1993 to 1998. From 1999 to 2004, subjects were interviewed regarding environmental tobacco smoke exposure before and after age 18 and the presence and duration of current symptoms of chronic cough and phlegm production and asthma diagnosis.
Results
Among 35,000 never smokers, fewer had smoking mothers (19%) than fathers (48%). Although few subjects currently lived (20%) or worked (4%) with smokers, 65% reported living with a daily smoker before age 18 years. Living with a smoker before age 18 increased the odds of chronic dry cough (149 cases, OR = 2.1, 95% CI 1.4–3.3) and, to a lesser extent, phlegm, after adjustment for age, gender, dialect group and current and past exposure to smokers at home and at work after age 18. Associations strengthened with higher numbers of smokers in childhood. There was no association with asthma or chronic bronchitis. We found suggestive evidence of a stronger association among subjects with lower adult intake of fiber, which we previously found to be protective for respiratory symptoms.
Conclusions
In this large study of nonsmokers, living with a smoker in childhood was associated with chronic dry cough and phlegm in adulthood, independently of later exposures to environmental tobacco smoke.
doi:10.1136/thx.2005.042960
PMCID: PMC1414787  PMID: 16131525
Tobacco smoke pollution; asthma; Signs and Symptoms; Respiratory; Bronchitis; chronic; Dietary Fiber
9.  Childhood exposure to environmental tobacco smoke and chronic respiratory symptoms in non-smoking adults: The Singapore Chinese Health Study 
Thorax  2005;60(12):1052-1058.
Background: Childhood exposure to environmental tobacco smoke has been extensively associated with childhood respiratory illness; fewer studies have addressed the effects on adults.
Methods: Childhood environmental tobacco smoke exposure in relation to chronic cough, phlegm, and asthma diagnosis was studied in never smokers from a cohort of Singaporeans of Chinese ethnicity aged 45–74 years at enrolment from 1993 to 1998. From 1999 to 2004 subjects were interviewed regarding environmental tobacco smoke exposure before and after the age of 18 and the presence and duration of current symptoms of chronic cough and phlegm production and asthma diagnosis.
Results: Among 35 000 never smokers, fewer had smoking mothers (19%) than fathers (48%). Although few subjects currently lived (20%) or worked (4%) with smokers, 65% reported living with a daily smoker before the age of 18 years. Living with a smoker before the age of 18 increased the odds of chronic dry cough (149 cases, odds ratio 2.1, 95% CI 1.4 to 3.3) and, to a lesser extent, phlegm, after adjustment for age, sex, dialect group, and current and past exposure to smokers at home and at work after the age of 18. Associations strengthened with higher numbers of smokers in childhood. There was no association with asthma or chronic bronchitis. There was evidence to suggest a stronger association among subjects with a lower adult intake of fibre which has previously been found to be protective for respiratory symptoms.
Conclusions: In this large study of non-smokers, living with a smoker in childhood was associated with chronic dry cough and phlegm in adulthood, independent of later exposures to environmental tobacco smoke.
doi:10.1136/thx.2005.042960
PMCID: PMC1414787  PMID: 16131525
10.  Air pollution and bronchitic symptoms in Southern California children with asthma. 
Environmental Health Perspectives  1999;107(9):757-760.
The association of air pollution with the prevalence of chronic lower respiratory tract symptoms among children with a history of asthma or related symptoms was examined in a cross-sectional study. Parents of a total of 3,676 fourth, seventh, and tenth graders from classrooms in 12 communities in Southern California completed questionnaires that characterized the children's histories of respiratory illness and associated risk factors. The prevalences of bronchitis, chronic phlegm, and chronic cough were investigated among children with a history of asthma, wheeze without diagnosed asthma, and neither wheeze nor asthma. Average ambient annual exposure to ozone, particulate matter (PM(10) and PM(2.5); [less than/equal to] 10 microm and < 2.5 microm in aerodynamic diameter, respectively), acid vapor, and nitrogen dioxide (NO(2)) was estimated from monitoring stations in each community. Positive associations between air pollution and bronchitis and phlegm were observed only among children with asthma. As PM(10) increased across communities, there was a corresponding increase in the risk per interquartile range of bronchitis [odds ratio (OR) 1.4/19 microg/m(3); 95% confidence interval (CI), 1.1-1.8). Increased prevalence of phlegm was significantly associated with increasing exposure to all ambient pollutants except ozone. The strongest association was for NO(2), based on relative risk per interquartile range in the 12 communities (OR 2.7/24 ppb; CI, 1.4-5.3). The results suggest that children with a prior diagnosis of asthma are more likely to develop persistent lower respiratory tract symptoms when exposed to air pollution in Southern California.
Images
PMCID: PMC1566453  PMID: 10464077
11.  Mould/dampness exposure at home is associated with respiratory disorders in Italian children and adolescents: the SIDRIA-2 Study 
Aims: To report on the relation between home mould and/or dampness exposure and respiratory disorders in a large sample of children and adolescents in Italy, accounting for age at time of exposure.
Methods: 20 016 children (mean age 7 years) and 13 266 adolescents (mean age 13 years) completed questionnaires on indoor exposures and respiratory symptoms/diseases. Statistical analyses were adjusted for sex, age, questionnaire's compiler, area of residence, season of interview, parental educational status, family history of asthma, rhinitis, eczema, chronic obstructive pulmonary disease, presence of gas water heaters, passive smoking, pets, and active smoking (only for adolescents). Population attributable risk % (PAR) was also computed.
Results: Asthma was more strongly related to only early than to only current exposure, both in children (OR 1.80, 95% CI 1.41 to 2.30) and adolescents (OR 1.89, 95% CI 1.38 to 2.59). The same result was found for rhino-conjunctivitis (OR 1.46, 95% CI 1.17 to 1.82), in children, and for wheeze among adolescents (OR 1.56, 95% CI 1.15 to 2.11). In children, wheeze (OR 1.98, 95% CI 1.47 to 2.66) and eczema (OR 1.44, 95% CI 1.09 to 1.91) were more strongly related to mould/dampness when exposed both early and currently; the same occurred in adolescents for rhino-conjunctivitis (1.78, 95% CI 1.30 to 2.45). Although persistent cough/phlegm was significantly related to mould/dampness exposure in children, regardless of exposure timing, no significant association between mould/dampness exposure and eczema or cough/phlegm was found among adolescents. PAR estimates were higher for only early than only current exposures. Avoiding early only exposure would abate wheeze by 6%, asthma or cough/phlegm by 7%, rhino-conjunctivitis in children by 4%, and in adolescents, asthma by 6%, and wheeze by 4%.
Conclusions: Respiratory disorders such as wheeze and asthma can often be explained by exposure to home mould/dampness, especially early in life. The association seems more evident in children than in adolescents. These findings may suggest the need for environmental prevention strategies.
doi:10.1136/oem.2004.018291
PMCID: PMC1741087  PMID: 16109818
12.  Effect of ambient levels of smoke and sulphur dioxide on the health of a national sample of 23 year old subjects in 1981. 
Thorax  1995;50(7):764-768.
BACKGROUND--There is concern that, despite the fall in air pollution levels since the 1950s, there may still be adverse effects at current levels. A study was carried out to investigate the association between air pollution and respiratory symptoms in 23 year old subjects in 1981. METHODS--Data on cough, phlegm, and wheeze were available on 11,552 members of the 1958 national birth cohort. Counties in the UK were ranked by annual average level of black smoke and sulphur dioxide (SO2), and then divided into five groups. The subject's county of residence determined their categorisation of pollution exposure. The association between air pollution exposure and respiratory symptoms was examined by logistic regression, adjusting for social class, sex, and smoking. RESULTS--The ranges of the air pollution groups were 2.0-13.0, 13.1-18.7, 19.6-20.8, 21.0-25.8, and 26.1-55.1 micrograms/m3 for black smoke, and 7.0-36.4, 36.7-42.7, 43.0-50.5, 52.0-59.3, and 60.9-87.7 micrograms/m3 for SO2. The overall prevalences of cough, phlegm, wheezing since age 16, and wheezing in the past year were 13.3%, 10.3%, 9.4%, and 4.4%, respectively. Phlegm symptoms increased with increasing smoke levels with evidence of a plateau. Cough and wheeze were not associated with black smoke; no symptom was associated with SO2. In the subgroup with wheeze at ages 16-23 there was no effect of smoke level on phlegm. CONCLUSIONS--Low ambient levels of black smoke were associated with decreased prevalence of phlegm symptoms in young adults in the UK in 1981. The effect was evident below the current EC guideline of 34-51 micrograms/m3 annual black smoke. In 1991 the annual mean smoke level for each county ranged from 3.4 to 26.5 micrograms/m3, spanning all but the last exposure group used here. This is consistent with the existence of adverse and possibly chronic effects at current levels.
PMCID: PMC474650  PMID: 7570412
13.  Association of Adenotonsillectomy with Asthma Outcomes in Children: A Longitudinal Database Analysis 
PLoS Medicine  2014;11(11):e1001753.
Rakesh Bhattacharjee and colleagues use data from a US private health insurance database to compare asthma severity measures in children one year before and one year after they underwent adenotonsillectomy with asthma measures in those who did not undergo adenotonsillectomy.
Please see later in the article for the Editors' Summary
Background
Childhood asthma and obstructive sleep apnea (OSA), both disorders of airway inflammation, were associated in recent observational studies. Although childhood OSA is effectively treated by adenotonsillectomy (AT), it remains unclear whether AT also improves childhood asthma. We hypothesized that AT, the first line of therapy for childhood OSA, would be associated with improved asthma outcomes and would reduce the usage of asthma therapies in children.
Methods and Findings
Using the 2003–2010 MarketScan database, we identified 13,506 children with asthma in the United States who underwent AT. Asthma outcomes during 1 y preceding AT were compared to those during 1 y following AT. In addition, 27,012 age-, sex-, and geographically matched children with asthma without AT were included to examine asthma outcomes among children without known adenotonsillar tissue morbidity. Primary outcomes included the occurrence of a diagnostic code for acute asthma exacerbation (AAE) or acute status asthmaticus (ASA). Secondary outcomes included temporal changes in asthma medication prescriptions, the frequency of asthma-related emergency room visits (ARERs), and asthma-related hospitalizations (ARHs). Comparing the year following AT to the year prior, AT was associated with significant reductions in AAE (30.2%; 95% CI: 25.6%–34.3%; p<0.0001), ASA (37.9%; 95% CI: 29.2%–45.6%; p<0.0001), ARERs (25.6%; 95% CI: 16.9%–33.3%; p<0.0001), and ARHs (35.8%; 95% CI: 19.6%–48.7%; p = 0.02). Moreover, AT was associated with significant reductions in most asthma prescription refills, including bronchodilators (16.7%; 95% CI: 16.1%–17.3%; p<0.001), inhaled corticosteroids (21.5%; 95% CI: 20.7%–22.3%; p<0.001), leukotriene receptor antagonists (13.4%; 95% CI: 12.9%–14.0%; p<0.001), and systemic corticosteroids (23.7%; 95% CI: 20.9%–26.5%; p<0.001). In contrast, there were no significant reductions in these outcomes in children with asthma who did not undergo AT over an overlapping follow-up period. Limitations of the MarketScan database include lack of information on race and obesity status. Also, the MarketScan database does not include information on children with public health insurance (i.e., Medicaid) or uninsured children.
Conclusions
In a very large sample of privately insured children, AT was associated with significant improvements in several asthma outcomes. Contingent on validation through prospectively designed clinical trials, this study supports the premise that detection and treatment of adenotonsillar tissue morbidity may serve as an important strategy for improving asthma control.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
The global burden of asthma has been rising steadily over the past few decades. Nowadays, about 200–300 million adults and children worldwide are affected by asthma, a chronic condition caused by inflammation of the airways (the tubes that carry air in and out of the lungs). Although asthma can develop at any age, it is often diagnosed in childhood—asthma is one of the commonest chronic diseases in children. In the US, for example, asthma affects around 7.1 million children under the age of 18 years and is the third leading cause of hospitalization of children under the age of 15 years. In people with asthma, the airways can react very strongly to allergens such as animal fur or to irritants such as cigarette smoke. Exercise, cold air, and infections can trigger asthma attacks, which can be fatal. The symptoms of asthma include wheezing, coughing, chest tightness, and shortness of breath. Asthma cannot be cured, but drugs can relieve its symptoms and prevent acute asthma attacks.
Why Was This Study Done?
Recent studies have found an association between severe childhood asthma and obstructive sleep apnea (OSA). In OSA, airway inflammation promotes hypertrophy (excess growth) of the adenoids and the tonsils, immune system tissues in the upper airway. During sleep, the presence of hypertrophic adenotonsillar tissues predisposes the walls of the throat to collapse, which results in apnea—a brief interruption in breathing. People with OSA often snore loudly and frequently wake from deep sleep as they struggle to breathe. Childhood OSA, which affects 2%–3% of children, can be effectively treated by removal of the adenoids and tonsils (adenotonsillectomy). Given the association between childhood OSA and severe asthma and given the involvement of airway inflammation in both conditions, might adenotonsillectomy also improve childhood asthma? Here, the researchers analyze data from the MarketScan database, a large database of US patients with private health insurance, to investigate whether adenotonsillectomy is associated with improvements in asthma outcomes and with reductions in the use of asthma therapies in children.
What Did the Researchers Do and Find?
The researchers used the database to identify 13,506 children with asthma who had undergone adenotonsillectomy and to obtain information about asthma outcomes among these children for the year before and the year after the operation. Because asthma severity tends to decrease with age, the researchers also used the database to identify 27,012 age-, sex-, and geographically matched children with asthma who did not have the operation so that they could examine asthma outcomes over an equivalent two-year period in the absence of complications related to adenotonsillar hypertrophy. Comparing the year after adenotonsillectomy with the year before the operation, adenotonsillectomy was associated with a 30% reduction in acute asthma exacerbations, a 37.9% reduction in acute status asthmaticus (an asthma attack that is unresponsive to the drugs usually used to treat attacks), a 25.6% reduction in asthma-related emergency room visits, and a 35.8% reduction in asthma-related hospitalizations. By contrast, among the control children, there was only a 2% reduction in acute asthma exacerbations and only a 7% reduction in acute status asthmaticus over an equivalent two-year period. Adenotonsillectomy was also associated with significant reductions (changes unlikely to have occurred by chance) in prescription refills for most types of drugs used to treat asthma, whereas there were no significant reductions in prescription refills among children with asthma who had not undergone adenotonsillectomy. The study was limited by the lack of measures of race and obesity, which are both associated with severity of asthma.
What Do These Findings Mean?
These findings show that in a large sample of privately insured children in the US, adenotonsillectomy was associated with significant improvements in several asthma outcomes. These results do not show, however, that adenotonsillectomy caused a reduction in the severity of childhood asthma. It could be that the children who underwent adenotonsillectomy (but not those who did not have the operation) shared another unknown factor that led to improvements in their asthma over time. To prove a causal link, it will be necessary to undertake a randomized controlled trial in which the outcomes of groups of children with asthma who are chosen at random to undergo or not undergo adenotonsillectomy are compared. However, with the proviso that there are some risks associated with adenotonsillectomy, these findings suggest that the detection and treatment of adenotonsillar hypertrophy may help to improve asthma control in children.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001753.
The US Centers for Disease Control and Prevention provides information on asthma, including videos, games, and links to other resources for children with asthma
The American Lung Association provides detailed information about asthma and a fact sheet on asthma in children; it also has information about obstructive sleep apnea
The National Sleep Foundation provides information on snoring and obstructive sleep apnea in children
The UK National Health Service Choices website provides information (including some personal stories) about asthma, about asthma in children, and about obstructive sleep apnea
The “Global Asthma Report 2014” will be available in October 2014
MedlinePlus provides links to further information on asthma, on asthma in children, on sleep apnea, and on tonsils and adenoids (in English and Spanish)
doi:10.1371/journal.pmed.1001753
PMCID: PMC4219664  PMID: 25369282
14.  Respiratory symptoms and illnesses among brick kiln workers: a cross sectional study from rural districts of Pakistan 
BMC Public Health  2012;12:999.
Background
Occupational risk factors are one of the major causes of respiratory illnesses and symptoms, and account for 13% of chronic obstructive pulmonary disease and 11% of asthma worldwide. Majority of brick kilns in Pakistan use wood and coal for baking the bricks which makes the brick kiln workers susceptible to high exposure of air pollution. This study was designed to describe frequency of chronic respiratory symptoms and illnesses and study the association between these symptoms and different types of work.
Methods
This was a questionnaire based cross sectional survey conducted among the brick kiln workers in Larkana and Dadu districts, Sindh, Pakistan. A total of 340 adult men were assessed using translated version of the American Thoracic Society Division of Lung Disease (ATS-DLD) questionnaire. Logistic regression analysis was done to determine the relationship between various socio-demographic and occupational factors (age, education, type of work, number of years at work, smoking status), and the respiratory symptoms and illnesses (chronic cough, chronic phlegm, wheeze, Chronic Bronchitis and asthma).
Results
Results of the study show that 22.4% workers had chronic cough while 21.2% reported chronic phlegm. 13.8% had two or more attacks of shortness of breath with wheezing. 17.1% workers were suffering from Chronic Bronchitis while 8.2% reported physician diagnosed asthma. Amongst the non-smoking workers 8.9% had Chronic Bronchitis. Multivariate analysis found that workers involved in brick baking were more likely to have Chronic Bronchitis (OR= 3.7, 95% CI 1.1-11.6, p=<0.05) and asthma (OR= 3.9, 95% CI 1.01-15.5, p=<0.05) compared to those involved in carriage and placement work.
Conclusion
A high frequency of respiratory symptoms and illnesses was observed among brick kiln workers. Age, nature of work and smoking were strong predictors of developing these symptoms and illnesses.
doi:10.1186/1471-2458-12-999
PMCID: PMC3507845  PMID: 23164428
Brick kiln workers; Pakistan; Respiratory symptoms and illnesses; Chronic bronchitis; Asthma
15.  Respiratory Effects of Marijuana and Tobacco Use in a U.S. Sample 
OBJECTIVE
Although a number of studies have examined the respiratory impact of marijuana smoking, such studies have generally used convenience samples of marijuana and tobacco users. The current study examined respiratory effects of marijuana and tobacco use in a nationally representative sample while controlling for age, gender, and current asthma.
DESIGN
Analysis of the nationally representative third National Health and Nutrition Examination Survey (NHANES III).
SETTING
U.S. households.
PARTICIPANTS
A total of 6,728 adults age 20 to 59 who completed the drug, tobacco, and health sections of the NHANES III questionnaire in 1988 and 1994. Current marijuana use was defined as self-reported 100+ lifetime use and at least 1 day of use in the past month.
MEASUREMENTS AND MAIN RESULTS
Self-reported respiratory symptoms included chronic bronchitis, frequent phlegm, shortness of breath, frequent wheezing, chest sounds without a cold, and pneumonia. A medical exam also provided an overall chest finding and a measure of reduced pulmonary functioning. Marijuana use was associated with respiratory symptoms of chronic bronchitis (P =.02), coughing on most days (P =.001), phlegm production (P =.0005), wheezing (P <.0001), and chest sounds without a cold (P =.02).
CONCLUSION
The impact of marijuana smoking on respiratory health has some significant similarities to that of tobacco smoking. Efforts to prevent and reduce marijuana use, such as advising patients to quit and providing referrals for support and assistance, may have substantial public health benefits associated with decreased respiratory health problems.
doi:10.1111/j.1525-1497.2004.40081.x
PMCID: PMC1490047  PMID: 15693925
marijuana; tobacco; smoking; respiratory symptoms; epidemiology
16.  A community survey of respiratory disease among East Indian and African adults in Guyana 
Thorax  1971;26(3):331-338.
The belief that chronic bronchitis is more prevalent among Indians than Africans in the Caribbean area was investigated by a community survey in Guyana. Respiratory symptoms were assessed by a standard questionnaire, ventilatory capacities were measured, and chest radiographs were taken of some 800 African and Indian men and women aged 35 to 54 years living in adjacent and similar communities. Histories of morning cough, chronic cough, morning phlegm, and chronic phlegm (chronic bronchitis) were more common in Indians than Africans. Although these respiratory symptoms were much more common in smokers than non-smokers, the higher prevalence rates in Indians could not be explained by smoking habits which were similar in the two races. Chronic bronchitis occurred in 17·3% of Indian and 2·4% of African male smokers and in 16·1% and 2·2% of Indian and African female non-smokers respectively. Judging by the history, lung function, and clinical signs, chronic bronchitis was more severe in Indians than Africans. The condition was more common among field labourers on sugar estates but, although the majority of field labourers were Indian, this occupational difference only partially explained the difference in prevalence between Indians and Africans. Indians, for reasons unknown, appear to have a greater susceptibility than Africans to chronic bronchitis.
PMCID: PMC1019092  PMID: 5089501
17.  Outcome of children of parents with atopic asthma and transient childhood wheezy bronchitis 
Thorax  1997;52(11):953-957.
BACKGROUND: Childhood asthma and wheeze only in the presence of respiratory infection (wheezy bronchitis) appear to have different prognoses and may differ in their aetiology and heritability. In particular, slight reductions in lung function may be associated with episodes of wheezing associated with intercurrent viral infection. METHODS: Outcomes for wheezing symptoms and lung function were studied in 133 offspring of three distinct groups of 69 middle aged probands with childhood histories of (1) atopic asthma (n = 18), (2) wheeze associated with upper respiratory tract infection (wheezy bronchitis, n = 24), and (3) no symptoms (n = 27). Probands were selected from a previously studied cohort in which outcomes of wheezy bronchitis and asthma had been shown to differ. RESULTS: Children of probands with wheezy bronchitis had a lower prevalence of current wheezing symptoms. Forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) in boys of probands with a history of wheezy bronchitis were significantly reduced compared with either of the other two groups (p < 0.0001). In a multivariate analysis, grouping based on parent proband had a significant effect on lung function, independent of factors such as symptoms, atopy or smoking history. CONCLUSIONS: The different symptomatic and lung function outcome in children of probands with wheezy bronchitis and asthma provides further evidence that wheezy bronchitis and asthma differ in their natural history and heritability, and suggests that there may be familial factors specific to each wheezing syndrome. 



PMCID: PMC1758443  PMID: 9487342
18.  Self reported respiratory symptoms and diseases among hairdressers. 
OBJECTIVES: Hairdressers are exposed to many irritative and allergenic substances capable of causing occupational respiratory symptoms and diseases. The self reported prevalence of respiratory symptoms and diseases was studied, and the risks among hairdressers compared with saleswomen was estimated. METHODS: A cross sectional prevalence study of respiratory symptoms and diseases was carried out among hairdressers and supermarket saleswomen, with a computer assisted telephone interview method (CATI). The study population comprised all the female hairdressers and supermarket saleswomen aged 15-54 years in the Helsinki metropolitan area, Finland. Disproportionate random samples of female hairdressers and sales-women were drawn from the trade union membership registers. The interviews were carried out between February and April 1994. A response rate of 80.5% (355/440) was obtained for hairdressers and 82.2% (583/709) for saleswomen. Atopy, smoking, chronic illnesses, type of work, working hours, working conditions, personal and professional use of hair products, and the use of personal protective devices were assessed. The outcome variables were self reported symptoms of the upper and lower respiratory tract. These were used to define chronic bronchitis, and asthma, laryngitis, and allergic rhinitis diagnosed by a physician. RESULTS: There was a considerable difference in the prevalence of chronic bronchitis; 6.8% in hairdressers versus 1.9% in saleswomen. The odds ratio (OR) adjusted for age, smoking, and atopy for chronic bronchitis indicated an increased risk of chronic bronchitis (OR 4.8, 95% confidence interval (95% CI) 2.2 to 10.1). No association was found between work as a hairdresser and asthma, laryngitis, and allergic rhinitis. Also the prevalence of rhinitis, rhinitis with eye symptoms, cough with phlegm, dyspnoea, and dyspnoea accompanied by cough was increased among hairdressers. The corresponding adjusted risk ORs were 1.7 (95% CI 1.3 to 2.3) for rhinitis, 1.9 (95% CI 1.4 to 2.6) for rhinitis with eye symptoms, 1.4 (CI 1.1 to 1.9) for cough with phlegm, 1.5 (95% CI 1.0 to 2.2) for dyspnoea, and 1.6 (95% CI 1.0 to 2.7) for dyspnoea with cough. CONCLUSIONS: Our results indicate an increased prevalence of upper and lower respiratory symptoms among hairdressers. Allergenic and irritative chemicals in hairdressing are likely candidates explaining the difference found between the hairdressers and controls. Work related reasons should be considered when a hairdresser presents with airway symptoms. Preventive actions are needed to improve the working conditions and personal protection.
PMCID: PMC1128807  PMID: 9245953
19.  Prevalence of chronic cough and phlegm among male cigar and pipe smokers: results of the Scottish Heart Health Study. 
Thorax  1993;48(11):1163-1167.
BACKGROUND--Previous studies investigating the effect of cigar or pipe smoking on the occurrence of chronic cough and chronic phlegm have reported prevalences among cigar and pipe smokers lying between those of non-smokers and current cigarette smokers. This study uses data on previous cigarette consumption, current cigar or pipe consumption, and biochemical markers of smoking to provide a detailed analysis of chronic cough and chronic phlegm among cigar and pipe smokers. METHODS--A total of 10,359 men and women aged 40-59 years were sampled for the Scottish Heart Health Study between 1984 and 1986. Prevalence of chronic cough and chronic phlegm among male cigar and pipe smokers (non-cigarette smokers) was compared with those who had never smoked, between ex-smokers of cigarettes and those who had never smoked cigarettes, between cigar-only and pipe-only smokers, and by cigar or pipe consumption levels. RESULTS--In all, 463 ex-smokers of cigarettes and 154 who had never smoked cigarettes were cigar or pipe smokers; 1080 had never smoked any form of tobacco. Ex-cigarette smokers smoked and inhaled more than those who had never smoked cigarettes. Among the ex-cigarette smokers, cigar or pipe smokers had 1.63-1.71 times the prevalence of both chronic cough and chronic phlegm than those who had never smoked (1.31-1.36 among cigar only smokers; 2.23-2.84 among pipe only smokers). A strong positive dose-response effect was found between the prevalence of symptoms and cigar or pipe consumption. CONCLUSIONS--Cigar and pipe smokers have a higher prevalence of chronic cough and phlegm than those who have never smoked, and the difference is more marked in pipe-only smokers than in cigar-only smokers. Both categories show a positive dose-response effect. Among cigar and pipe smokers, ex-cigarette smokers have a higher prevalence of symptoms than those who have never smoked cigarettes, which may be because they inhale more or may be attributable to previous cigarette smoking.
PMCID: PMC464910  PMID: 8296263
20.  Effects of BMI, Fat Mass, and Lean Mass on Asthma in Childhood: A Mendelian Randomization Study 
PLoS Medicine  2014;11(7):e1001669.
In this study, Granell and colleagues used Mendelian randomization to investigate causal effects of BMI, fat mass, and lean mass on current asthma at age 7½ years in the Avon Longitudinal Study of Parents and Children (ALSPAC) and found that higher BMI increases the risk of asthma in mid-childhood.
Please see later in the article for the Editors' Summary
Background
Observational studies have reported associations between body mass index (BMI) and asthma, but confounding and reverse causality remain plausible explanations. We aim to investigate evidence for a causal effect of BMI on asthma using a Mendelian randomization approach.
Methods and Findings
We used Mendelian randomization to investigate causal effects of BMI, fat mass, and lean mass on current asthma at age 7½ y in the Avon Longitudinal Study of Parents and Children (ALSPAC). A weighted allele score based on 32 independent BMI-related single nucleotide polymorphisms (SNPs) was derived from external data, and associations with BMI, fat mass, lean mass, and asthma were estimated. We derived instrumental variable (IV) estimates of causal risk ratios (RRs). 4,835 children had available data on BMI-associated SNPs, asthma, and BMI. The weighted allele score was strongly associated with BMI, fat mass, and lean mass (all p-values<0.001) and with childhood asthma (RR 2.56, 95% CI 1.38–4.76 per unit score, p = 0.003). The estimated causal RR for the effect of BMI on asthma was 1.55 (95% CI 1.16–2.07) per kg/m2, p = 0.003. This effect appeared stronger for non-atopic (1.90, 95% CI 1.19–3.03) than for atopic asthma (1.37, 95% CI 0.89–2.11) though there was little evidence of heterogeneity (p = 0.31). The estimated causal RRs for the effects of fat mass and lean mass on asthma were 1.41 (95% CI 1.11–1.79) per 0.5 kg and 2.25 (95% CI 1.23–4.11) per kg, respectively. The possibility of genetic pleiotropy could not be discounted completely; however, additional IV analyses using FTO variant rs1558902 and the other BMI-related SNPs separately provided similar causal effects with wider confidence intervals. Loss of follow-up was unlikely to bias the estimated effects.
Conclusions
Higher BMI increases the risk of asthma in mid-childhood. Higher BMI may have contributed to the increase in asthma risk toward the end of the 20th century.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
The global burden of asthma, a chronic (long-term) condition caused by inflammation of the airways (the tubes that carry air in and out of the lungs), has been rising steadily over the past few decades. It is estimated that, nowadays, 200–300 million adults and children worldwide are affected by asthma. Although asthma can develop at any age, it is often diagnosed in childhood—asthma is the most common chronic disease in children. In people with asthma, the airways can react very strongly to allergens such as animal fur or to irritants such as cigarette smoke, becoming narrower so that less air can enter the lungs. Exercise, cold air, and infections can also trigger asthma attacks, which can be fatal. The symptoms of asthma include wheezing, coughing, chest tightness, and shortness of breath. Asthma cannot be cured, but drugs can relieve its symptoms and prevent acute asthma attacks.
Why Was This Study Done?
We cannot halt the ongoing rise in global asthma rates without understanding the causes of asthma. Some experts think obesity may be one cause of asthma. Obesity, like asthma, is increasingly common, and observational studies (investigations that ask whether individuals exposed to a suspected risk factor for a condition develop that condition more often than unexposed individuals) in children have reported that body mass index (BMI, an indicator of body fat calculated by dividing a person's weight in kilograms by their height in meters squared) is positively associated with asthma. Observational studies cannot prove that obesity causes asthma because of “confounding.” Overweight children with asthma may share another unknown characteristic (confounder) that actually causes both obesity and asthma. Moreover, children with asthma may be less active than unaffected children, so they become overweight (reverse causality). Here, the researchers use “Mendelian randomization” to assess whether BMI has a causal effect on asthma. In Mendelian randomization, causality is inferred from associations between genetic variants that mimic the effect of a modifiable risk factor and the outcome of interest. Because gene variants are inherited randomly, they are not prone to confounding and are free from reverse causation. So, if a higher BMI leads to asthma, genetic variants associated with increased BMI should be associated with an increased risk of asthma.
What Did the Researchers Do and Find?
The researchers investigated causal effects of BMI, fat mass, and lean mass on current asthma at age 7½ years in 4,835 children enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC, a long-term health project that started in 1991). They calculated an allele score for each child based on 32 BMI-related genetic variants, and estimated associations between this score and BMI, fat mass and lean mass (both measured using a special type of X-ray scanner; in children BMI is not a good indicator of “fatness”), and asthma. They report that the allele score was strongly associated with BMI, fat mass, and lean mass, and with childhood asthma. The estimated causal relative risk (risk ratio) for the effect of BMI on asthma was 1.55 per kg/m2. That is, the relative risk of asthma increased by 55% for every extra unit of BMI. The estimated causal relative risks for the effects of fat mass and lean mass on asthma were 1.41 per 0.5 kg and 2.25 per kg, respectively.
What Do These Findings Mean?
These findings suggest that a higher BMI increases the risk of asthma in mid-childhood and that global increases in BMI toward the end of the 20th century may have contributed to the global increase in asthma that occurred at the same time. It is possible that the observed association between BMI and asthma reported in this study is underpinned by “genetic pleiotropy” (a potential limitation of all Mendelian randomization analyses). That is, some of the genetic variants included in the BMI allele score could conceivably also increase the risk of asthma. Nevertheless, these findings suggest that public health interventions designed to reduce obesity may also help to limit the global rise in asthma.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001669.
The US Centers for Disease Control and Prevention provides information on asthma and on all aspects of overweight and obesity (in English and Spanish)
The World Health Organization provides information on asthma and on obesity (in several languages)
The UK National Health Service Choices website provides information about asthma, about asthma in children, and about obesity (including real stories)
The Global Asthma Report 2011 is available
The Global Initiative for Asthma released its updated Global Strategy for Asthma Management and Prevention on World Asthma Day 2014
Information about the Avon Longitudinal Study of Parents and Children is available
MedlinePlus provides links to further information on obesity in children, on asthma, and on asthma in children (in English and Spanish
Wikipedia has a page on Mendelian randomization (note: Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
doi:10.1371/journal.pmed.1001669
PMCID: PMC4077660  PMID: 24983943
21.  Cigarette tar content and symptoms of chronic bronchitis: results of the Scottish Heart Health Study. 
STUDY OBJECTIVE--The aim was to determine if there was a relationship between cigarette tar yield and rates of chronic cough and chronic phlegm. SETTING--22 districts across Scotland were used for the Scottish Heart Health Study (SHHS) which was conducted between 1984 and 1986 and from which the data for this analysis were obtained. SUBJECTS--10,359 men and women aged 40-59 years were studied. Of these, 2801 current cigarette smokers whose brand of cigarette smoked was known were selected. MEASUREMENTS AND MAIN RESULTS--Data on self reported smoking habits and prevalence of chronic cough and chronic phlegm were obtained from the SHHS. Tar yield was divided into three groups: low (less than or equal to 12 mg/cigarette); middle (13-14 mg/cigarette); high (greater than or equal to 15 mg/cigarette). The average tar yield consumed per person was 13.2 mg/cigarette. Women in the middle and high tar groups had smoked for longer and had significantly higher breath carbon monoxide levels, serum thiocyanate levels, serum cotinine levels, and daily cigarette consumption than the women in the low tar group. This pattern was not seen in men for any of these five smoking variables. Rates of chronic cough and chronic phlegm were higher with higher tar yield of cigarettes smoked for women (low tar v high tar: p less than 0.001) but not for men. Daily cigarette consumption and the number of years of smoking were the most significant risk factors for chronic cough and chronic phlegm for both men and women. Tar was still a significant risk factor (p less than 0.05) for women after controlling for these two risk factors and social class. CONCLUSIONS--Both sexes show strong effects of daily cigarette consumption and years of smoking on respiratory symptoms; women show an additional effect of cigarette tar content while men do not. The spread of tar yield in both sexes was small but there were more women on low tar cigarettes and this may have enabled a weak effect of tar to be seen better in them. On the other hand, tar level in women was confounded with other factors. Statistical methods of controlling for this may not have removed this confounding completely.
PMCID: PMC1059462  PMID: 1795148
22.  Time trends in respiratory symptoms in childhood over a 24 year period. 
Archives of Disease in Childhood  1993;68(6):729-734.
Two cross sectional surveys, 24 years apart, using the same respiratory questionnaire, were carried out to examine changes in prevalence rates of cough, phlegm, and wheeze and to relate changes in wheeze to objective peak expiratory flow rates (PEFRs). The surveys were done in towns in southern and northern England and South Wales in schoolchildren aged 6.0-7.5 years; n = 1655 in 1966 and n = 2323 in 1990. Parents reported on winter cough and winter phlegm (early morning or day/night) and wheeze; PEFRs were also measured. The proportion of children reported as wheezing on most days or nights increased from 3.9% to 6.1% (95% confidence interval (CI) for increase -0.2 to 4.6), with a smaller increase in the prevalence of those who had ever wheezed. The proportion of children with day or night time cough increased from 21.1% to 33.3% (95% CI for increase 3.8 to 20.6) and the proportion with day or night time phlegm increased from 5.8% to 10.0% (95% CI for increase 0.4 to 8.0). Smaller increases in the prevalence of persistent cough (from 9.0% to 12.4%) and persistent phlegm (from 2.4% to 3.5%) were also observed, while morning cough and morning phlegm showed little change. The increases in cough and phlegm were apparent in subjects with and without a history of wheeze. Both absolute and proportional changes in symptom prevalence were generally greater in the north than in the south. Similar social class trends were seen in each survey. The mean difference in PEFR between subjects with and without wheeze was smaller in 1990 than in 1966, but this result could be influenced by a greater proportion of subjects receiving antiasthmatic treatment in the 1990 survey. These apparent increases in the prevalence of persistent wheeze, day and night time cough and phlegm, occurring over a period during which outdoor air pollution levels have decreased substantially, deserve further investigation.
PMCID: PMC1029362  PMID: 8333760
23.  Prevalence of chronic cough, chronic phlegm & associated factors in Mysore, Karnataka, India 
Background & objectives:
Chronic cough and chronic phlegm are important indicators of respiratory morbidity, accelerated lung function decline, increased hospitalization and mortality. This study was planned to estimate the prevalence of chronic cough and phlegm in the absence of dyspneoa and wheezing and to study its associated factors in a representative population of Mysore district.
Methods:
A cross-sectional survey was planned in a representative population of Mysore taluk. Eight villages were randomly selected based on the list of villages from census 2001. Trained field workers using the Burden of Obstructive Diseases questionnaire carried out a house-to-house survey.
Results:
A total of 4333 adult subjects were enrolled in the study with 2333 males and 2000 females. The prevalence of chronic cough in the community was 2.5 per cent and that of chronic phlegm was 1.2 per cent. A significant association was observed between chronic cough and age, gender, occupation and smoking and chronic phlegm with age, gender, occupation, indoor animals and smoking. A multivariate analysis confirmed independent association of age, occupation and smoking for chronic cough and age and smoking for chronic phlegm. On sub-group analysis of males, heavy smokers had higher prevalence of chronic cough and chronic phlegm as compared to light smokers and non smokers.
Interpretation & conclusions:
The prevalence of chronic cough was 2.5 per cent and chronic phlegm was 1.2 per cent in the general population in Mysore which is lower than that observed in other studies. Heavy smoking was an important preventable risk factor identified in this study and efforts towards smoking cessation are crucial to achieve good respiratory health in the community.
PMCID: PMC3171924  PMID: 21808140
Chronic cough; chronic phlegm; prevalence; tobacco smoking
24.  Accumulation of factors influencing respiratory illness in members of a national birth cohort and their offspring. 
STUDY OBJECTIVE--The aim was to investigate predictors of childhood lower respiratory tract illness in two generations, and predictors of adult lower respiratory disorders in the first generation. DESIGN--Data on respiratory health and environmental factors from a national birth cohort study were examined from birth to 36 years. Data were also collected on the parents of the subjects and on the subjects' first born offspring from birth to eight years. Main outcome measures were: reports of lower respiratory tract illness before 2 years; lower respiratory tract illness of a week or more between age 20 and 36 years; regular phlegm production at 25 and 36 years; reports of wheeze or asthma at age 36 years; peak expiratory flow rate (PEFR) at age 36 years measured by nurses during home visits; and mothers' reports of lower respiratory illness in first born offspring before 2 years. SUBJECTS--Subjects were a sample of 5362 single, legitimate births taken from all those occurring in England, Wales, and Scotland in one week in 1946, and studied regularly from birth to age 43 years. Data on the subjects' parents and on their 1676 first offspring born while they were aged 19-25 years were also collected. MAIN RESULTS--Lower respiratory tract illness before 2 years fell from 25% in the population born in 1946 to 13% in their first born offspring. In those born in 1946, poor home environment, parental bronchitis, and atmospheric pollution were the best predictors of lower respiratory illness before 2 years, and these three factors and childhood lower respiratory illness and later smoking were the best predictors of adult lower respiratory tract problems. Risk factors for lower respiratory illness in the offspring were manual social class, parental and grandparental lower respiratory disease, and parental smoking. CONCLUSIONS--Risks for adult lower respiratory problems accumulated in childhood through illness, poor social circumstances, and atmospheric pollution. Smoking exacerbated early life risks and was an independent risk factor. In the offspring generation, parental smoking was a risk factor for early life chest illness, together with parental illness and low social class. Reduction of prevalence in the offspring generation was probably accounted for by improvement in home circumstances, reduced atmospheric pollution, and lower rates of parental lower respiratory illness, but current rates of smoking seem likely to prevent much further reduction in early life lower respiratory illness, and thus in this aspect of risk for subsequent adult lower respiratory problems. The accumulation of risk in childhood and adolescence for later adult problems implies a long time scale for the reduction of adult lower respiratory disorders.
PMCID: PMC1059569  PMID: 1645088
25.  Chronic productive cough in school children: prevalence and associations with asthma and environmental tobacco smoke exposure 
Background
The relationships between chronic productive cough (CPC), environmental tobacco smoke (ETS) exposure, and asthma are not clearly established in children. Therefore, we wished to determine the prevalence of CPC and examine the relationships between CPC, ETS exposure, and asthma in young teenagers.
Methods
We performed a cross sectional survey of 2397 Seattle middle school students, 11–15 years old, using written and video respiratory-symptom questionnaires. We defined CPC as – daily cough productive of phlegm for at least 3 months out of the year; current asthma as – yes to "Have you had wheezing or whistling in your chest in the past 12 months?" and yes in the past year to any of the four video wheezing/asthma video scenarios; and ETS exposure as exposed to tobacco smoke at least several hours each day. We used multilogistic regression to examine relationships between CPC, asthma, and ETS exposure and included in the model the potentially confounding variables race, gender, and allergic rhinitis.
Results
The prevalence of CPC was 7.2%. Forty-seven percent (82/173) of children with CPC met criteria for current asthma, while only 10% (214/2224) of those without CPC had current asthma. Current asthma had the strongest associated with CPC, odds ratio (OR) 6.4 [95% CI 4.5–9.0], and ETS was independently associated with both CPC, OR 2.7 [1.8–4.1] and asthma, OR 2.7 [1.5–4.7].
Conclusion
In a population of young teenagers, CPC was strongly associated with report of current asthma symptoms and also with ETS exposure. This suggests that asthma and ETS exposure may contribute to CPC in children. However, this study was not designed to determine whether asthma was the actual cause of CPC in this population of children.
doi:10.1186/1745-9974-2-11
PMCID: PMC1770929  PMID: 17192188

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