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2.  Work-related asthma in Montreal, Quebec: Population attributable risk in a community-based study 
BACKGROUND:
Occupational exposures are an important cause of adult-onset asthma but the population attributable risk percentage (PAR%) has been less frequently studied.
OBJECTIVES:
To examine the distribution and determinants of adult asthma in six centres across Canada using data gathered in a community-based study.
METHODS:
Data were gathered in a community survey of 2959 adults using the European Community Respiratory Health Survey Protocol. A subsample of 498 subjects completed detailed health and occupational questionnaires, methacholine challenge tests and allergy skin tests. Asthma was defined in three ways: current wheeze, asthma symptoms and/or medication, and airway hyperresponsiveness. Occupational exposures were classified as sensitizers or irritants. Associations between asthma and occupational exposures were examined using logistic regression analysis. Model selection was based on the findings for current wheeze, and the same model was applied to the other definitions of asthma.
RESULTS:
Fifty-six per cent of subjects reported ever having had occupational exposure to sensitizers, and 9.8% to irritants. Current wheeze was associated with exposure to irritants (PAR% 4.54%), and airway hyperresponsiveness was associated with exposure to sensitizers (PAR% 30.7%). Neither a history of childhood asthma, atopy, nor confining the analysis to adult-onset asthma affected these associations. Analysis of effect modification suggested two types of work-related asthma: one due to exposure to occupational sensitizers, and the other due to exposure to irritants.
CONCLUSIONS:
Detailed assessment of past and current exposures is essential in the investigation of work-related asthma. Childhood asthma reactivated or aggravated by work exposures is not easy to distinguish from asthma induced by work, a misclassification that could lead to an underestimation of work-induced asthma. This should be taken into account in jurisdictions in which persons with work-aggravated asthma are not eligible for workers’ compensation.
PMCID: PMC2682161  PMID: 19107239
Healthy worker effect; Irritants; Population attributable risk; Sensitizers; Work-related asthma
3.  Airflow obstruction in young adults in Canada 
OBJECTIVE:
Airflow obstruction is relatively uncommon in young adults, and may indicate potential for the development of progressive disease. The objective of the present study was to enumerate and characterize airflow obstruction in a random sample of Canadians aged 20 to 44 years.
SETTING:
The sample (n=2962) was drawn from six Canadian sites.
DESIGN:
A prevalence study using the European Community Respiratory Health Survey protocol was conducted. Airflow obstruction was assessed by spirometry. Bronchial responsiveness, skin reactivity to allergens and total serum immunoglobulin E were also measured. Logistic regression was used for analysis.
RESULTS:
Airflow obstruction was observed in 6.4% of the sample, not associated with sex or age. The risk of airflow obstruction increased in patients who had smoked and in patients who had lung trouble during childhood. Adjusted for smoking, the risk of airflow obstruction was elevated for subjects with past and current asthma, skin reactivity to allergens, elevated levels of total immunoglobulin E and bronchial hyper-responsiveness. Of the subjects with airflow obstruction, 21% were smokers with a history of asthma, 50% were smokers without asthma, 12% were nonsmokers with asthma and 17% were nonsmokers with no history of asthma. Bronchial hyper-responsiveness increased the prevalence of airflow obstruction in each of these groups.
CONCLUSION:
Smoking and asthma, jointly and individually, are major determinants of obstructive disorders in young adults. Bronchial hyper-responsiveness contributes to obstruction in both groups.
PMCID: PMC2676367  PMID: 17551598
Airway obstruction; Obstructive lung disease; Risk factors; Young adults
4.  Childhood predictors of smoking in adolescence: a follow-up study of Montréal schoolchildren 
Background
The factors that cause children to become smokers in adolescence remain unclear. Although parental smoking and peer pressure may play a role, physiological factors such as lung volume have also been identified.
Methods
To investigate these and other possible childhood predictors of teenage smoking, we gathered follow-up data on 191 Montréal schoolchildren, aged 5–12 years (average 9.2 yr) when first examined. At an average age of 13.0 years, they answered further questions on their health and smoking behaviour and provided a second set of spirometric measurements.
Results
At the second survey, 80% of the children had entered high school and 44% had become smokers. Reaching puberty between the surveys was the most significant determinant of becoming a smoker: 56.4% of the 124 children postpubertal at the second survey had taken up smoking, versus 17.9% of the 67 who were still prepubertal (p = 0.001). We found salivary cotinine level, a measure of uptake of environmental tobacco smoke, to be an independent predictor of becoming a teenage smoker; even after adjustment for sex, socioeconomic status of parents, a crowding index, and the numbers at home of siblings, adult smokers and cigarettes smoked, it remained significant for both groups: postpubertal (odds ratio [OR] 1.2, 95% confidence interval [CI] 1.2–3.0) and prepubertal (OR 2.1, 95% CI 1.0– 4.5). The influence of forced vital capacity was marginally significant only in the postpubertal group (OR 5.0, 95% CI 0.88–28.3).
Interpretation
The proportion of nicotine absorbed from that available in environmental tobacco smoke during childhood is associated with subsequent smoking in adolescence. The more efficient absorption of nicotine seen in some children may be related to physiological factors such as lung capacity.
doi:10.1503/cmaj.1041428
PMCID: PMC1188223  PMID: 16103510
5.  Prevalence of asthma symptoms among adults aged 20–44 years in Canada 
Background
Reported prevalence rates of asthma vary within and between countries around the world. These differences suggest environmental factors in addition to genetic factors in the cause of the disease and may provide clues for preventive strategies. We examined the variability of asthma-related symptoms and medication use among adults in 6 sites across Canada (Vancouver, Winnipeg, Hamilton, Montreal, Halifax and Prince Edward Island) and compared our findings with those from sites that had participated in a recent European survey.
Methods
We used the same sampling strategy and standardized questionnaire as those used in the European Community Respiratory Health Survey (ECRHS). The 6 Canadian sites were selected to represent different environments with respect to climate, air pollution and occupational exposure. Community-based samples of 3000 to 4000 people aged 20–44 years were randomly selected in each site. Subjects were asked to complete the questionnaire by mail between March 1993 and November 1994. Prevalence rates (and 95% confidence intervals [CIs]) of asthma symptoms, self-reported asthma attacks and use of asthma medication were compared across the Canadian sites and with sites that had participated in the ECRHS.
Results
The overall response rate of those selected to receive the questionnaire was 86.5% (range 74.5%–92.8%). The prevalence rates of most asthma symptoms varied significantly among the Canadian sites. For instance, 21.9% (Montreal) to 30.4% (Halifax) of the men and 24.0% (Vancouver) to 35.2% (Halifax) of the women reported wheezing in the year before the survey. Depending on the site, 4.4% to 6.3% of the men and 5.2% to 9.5% of the women reported an asthma attack in the last year, and 4.0% to 6.1% of the men and 4.9% to 9.7% of the women were currently using asthma medication. Prevalence rates of symptoms, asthma attacks and medication use did not change with age, but they were higher among women than among men. Compared with the results from the ECRHS sites, those from the Canadian sites were among the highest.
Interpretation
Significant variation in the prevalence of asthma symptoms, asthma attacks and use of asthma medication between Canadian sites and international sites suggests environmental influences. Different combinations of factors in different sites may be responsible for the high prevalence rates and should be the subject of further research to guide clinical management and public health intervention.
PMCID: PMC80927  PMID: 11314453
6.  Rheumatic complaints and pulmonary response to chrysotile dust inhalation in the mines and mills of Quebec 
In 1967-68 an age-stratified random sample of 1069 current workers in Quebec asbestos mines and mills was surveyed. Questions concerning rheumatic complaints were included in a modified MRC questionnaire used at that time, and on this basis a rheumatic severity gradient was devised. No relationship could be detected between rheumatic complaints and pulmonary radiologic response to chrysotile dust exposure, despite implications in the literature that such a relationship might exist.
PMCID: PMC1947818  PMID: 4547295
7.  Commentaries 
PMCID: PMC1936180  PMID: 20328807
8.  Lung Cancer in a Fluorspar Mining Community. II. Prevalence of Respiratory Symptoms and Disability 
A survey of respiratory symptoms, lung function tests, and chest radiography was carried out among the fluorspar miners of St. Lawrence, Newfoundland, in whom the incidence of carcinoma of the lung (De Villiers and Windish, 1964) had previously been shown to be 25 times greater than for the rest of the province.
The incidence of pneumoconiosis among the exposed population was low (1·93%) and the incidence of `chronic bronchitis' comparable to that reported for miners elsewhere, enabling one to dismiss these as a relevant factor in the high incidence of carcinoma.
The relevance of smoking is less easy to assess in these miners, among whom there are few non-smokers and many heavy smokers. Extrapolation from the data of Doll and Hill (1956) suggests, however, that the prevalence of heavy smoking among the miners cannot be the sole factor responsible for the higher incidence of carcinoma compared with the rest of Newfoundland, but it might well be a contributory one. It appears therefore that the main factor causing the high incidence of carcinoma among these miners was the high level of radioactivity in the air and water in the mines (De Villiers and Windish, 1964).
The reduction in lung function tests appeared to be more closely related to the presence of bronchitis than to dust exposure, but the incidence of chronic bronchitis was apparently higher in men exposed for any length of time to dust risk than in men with insignificant exposure.
PMCID: PMC1038331  PMID: 14142516
10.  Studies on the Nature and Aetiology of Respiratory Disability in Witwatersrand Gold-Miners Free of Radiological Silicosis 
In an investigation into the cause of symptoms in gold-miners who have no radiological silicosis, the relationship of dyspnoea and physiological disturbances to dust exposure was examined. Forty-five subjects, aged 41 to 45 years, with normal chest radiographs and long service underground were chosen for study from the population of miners past and present. Thirty-four men only were tested, but the validity of the sample was checked by comparison with a similar group of miners reported previously.
Each individual's dust exposure was estimated in “particle-hours”. A detailed history, including smoking habits, was followed by a clinical examination and a battery of lung function tests in each case.
No significant relationship was found between dyspnoea and dust exposure or smoking. However, a negative correlation was observed between dust exposure and effort tests, implying that exercise capacity appeared best in those men whose dust exposure was greatest. Possible reasons for this finding are discussed.
On the other hand, dyspnoea did correlate with airway obstruction and hyperventilation on effort, indicating a physiological rather than a psychological basis for the symptoms. Further, the higher incidence of cough, sputum, and rhonchi in the more disabled subjects suggested that chronic bronchitis might be the basis of their symptoms, but the cause of the bronchitis remains to be identified. It seems that dust exposure alone was not the cause, but the findings do not exclude the possibility of its being related to the occupation of mining with stresses such as inhalation of fumes and rapid changes in temperature, humidity, and altitude.
PMCID: PMC1037967  PMID: 13798146
14.  A New Index of the Intrapulmonary Mixture of Inspired Air 
Thorax  1952;7(1):111-116.
PMCID: PMC1019145  PMID: 14913505

Results 1-15 (15)