Rationale: Asthma is prospectively associated with
age-related chronic diseases and mortality, suggesting the hypothesis that asthma may
relate to a general, multisystem phenotype of accelerated aging.
Objectives: To test whether chronic asthma is associated with a proposed
biomarker of accelerated aging, leukocyte telomere length.
Methods: Asthma was ascertained prospectively in the Dunedin
Multidisciplinary Health and Development Study cohort (n = 1,037) at nine
in-person assessments spanning ages 9–38 years. Leukocyte telomere length was
measured at ages 26 and 38 years. Asthma was classified as life-course-persistent,
childhood-onset not meeting criteria for persistence, and adolescent/adult-onset. We
tested associations between asthma and leukocyte telomere length using regression
models. We tested for confounding of asthma-leukocyte telomere length associations
using covariate adjustment. We tested serum C-reactive protein and white blood cell
counts as potential mediators of asthma-leukocyte telomere length associations.
Measurements and Main Results: Study members with life-course-persistent
asthma had shorter leukocyte telomere length as compared with sex- and age-matched
peers with no reported asthma. In contrast, leukocyte telomere length in study
members with childhood-onset and adolescent/adult-onset asthma was not different from
leukocyte telomere length in peers with no reported asthma. Adjustment for life
histories of obesity and smoking did not change results. Study members with
life-course-persistent asthma had elevated blood eosinophil counts. Blood eosinophil
count mediated 29% of the life-course-persistent asthma-leukocyte telomere length
Conclusions: Life-course-persistent asthma is related to a proposed
biomarker of accelerated aging, possibly via systemic eosinophilic inflammation. Life
histories of asthma can inform studies of aging.
asthma; telomere; aging; longitudinal; developmental phenotype
Impaired lung function is associated with systemic inflammation and is a risk factor for cardiovascular disease in older adults. It is unknown when these associations emerge and to what extent they are mediated by smoking, chronic airways disease, and/or established atherosclerosis. We explored the association between the forced expiratory volume in one second (FEV1) and the systemic inflammatory marker C‐reactive protein (CRP) in young adults.
Associations between spirometric lung function and blood CRP were assessed in a population based birth cohort of approximately 1000 New Zealanders at ages 26 and 32 years. Analyses adjusted for height and sex to account for differences in predicted lung function and excluded pregnant women.
There were significant inverse associations between FEV1 and CRP at both ages. Similar results were found for the forced vital capacity. These associations were similar in men and women and were independent of smoking, asthma, and body mass index.
Reduced lung function is associated with systemic inflammation in young adults. This association is not related to smoking, asthma, or obesity. The reasons for the association are unexplained, but the findings indicate that the association between lower lung function and increased inflammation predates the development of either chronic lung disease or clinically significant atherosclerosis. The association between poor lung function and cardiovascular disease may be mediated by an inflammatory mechanism.
inflammation; C‐reactive protein; spirometry; cohort studies
Research into social inequalities in health has tended to focus on low socioeconomic status in adulthood. We aimed to test the hypothesis that children’s experience of socioeconomic disadvantage is associated with a wide range of health risk factors and outcomes in adult life.
We studied an unselected cohort of 1000 children (born in New Zealand during 1972–73) who had been assessed at birth and ages 3, 5, 7, 9, 11, 13, and 15 years. At age 26 years, we assessed these individuals for health outcomes including body-mass index, waist:hip ratio, blood pressure, cardiorespiratory fitness, dental caries, plaque scores, gingival bleeding, periodontal disease, major depression, and tobacco and alcohol dependence, and tested for associations between these variables and childhood and adult socioeconomic status.
Compared with those from high socioeconomic status backgrounds, children who grew up in low socioeconomic status families had poorer cardiovascular health. Significant differences were also found on all dental health measures, with a threefold increase in adult periodontal disease (31·1% vs 11·9%) and caries level (32·2% vs 9·9%) in low versus high childhood socioeconomic status groups. Substance abuse resulting in clinical dependence was related in a similar way to childhood socioeconomic status (eg, 21·5% vs 12·1% for adult alcohol dependence). The longitudinal associations could not be attributed to life-course continuity of low socioeconomic status, and upward mobility did not mitigate or reverse the adverse effects of low childhood socioeconomic status on adult health.
Protecting children against the effects of socioeconomic adversity could reduce the burden of disease experienced by adults. These findings provide strong impetus for policy makers, practitioners, and researchers to direct energy and resources towards childhood as a way of improving population health.
The objective of the study was to examine the link between anxiety and allergies to establish whether it reflects a psychobiological reality or a possible methodological bias. A cohort of 1,037 children enrolled in the study. Anxiety disorders were assessed between 11 and 21 years. Anxious personality was assessed at 18 years. Allergies were examined at 21 years by (a) self reports, (b) skin pricks, and (c) serum total immunoglobulin E (IgE). Self-reported allergies were predicted by recurrent anxiety disorders (OR [95% CI]=1.56 [1.06–2.30], p=.023) and self-reports of anxious personality (OR [95% CI]=1.67 [1.17–2.37], p=.004): Objectively verified allergies were not. These results suggest that the link between anxiety and allergies may reflect a methodological artifact rather than a psychobiological reality.
In vitro studies have shown that p53 mediates a protective response against DNA damage by causing either cell-cycle arrest and DNA repair, or apoptosis. These responses have not yet been demonstrated in humans. A common source of DNA damage in humans is cigarette smoke, which should activate p53 repair mechanisms. The level of p53 is regulated by HDM2, which targets p53 for degradation. The G-allele of a polymorphism in intron 1 of HDM2 (rs2279744:G/T) results in higher HDM2 levels, and should be associated with a reduced p53 response and hence more DNA damage and corresponding tissue destruction. Similarly, the alleles of a polymorphism (rs1042522) in TP53 that encode arginine (G-allele) or proline (C-allele) at codon 72 cause increased pro-apoptotic (G-allele) or cell-cycle arrest activities (C-allele), respectively, and may moderate p53's ability to prevent DNA damage. To test these hypotheses we examined lung function in relation to cumulative history of smoking in a population-based cohort. The G-alleles in HDM2 and TP53 were found to be associated with accelerated smoking-related decline in lung function. These data support the hypothesis that p53 protects from DNA damage in humans and provides a potential explanation for variation in lung function impairment amongst smokers.
Exposure to traffic-related air pollution (TRAP) can adversely impact health but epidemiologic studies are limited in their abilities to assess long-term exposures and incorporate variability in indoor pollutant infiltration.
In order to examine settled house dust levels of hopanes, engine lubricating oil byproducts found in vehicle exhaust, as a novel TRAP exposure measure, dust samples were collected from 171 homes in five Canadian cities and analyzed by gas chromatography–mass spectrometry. To evaluate source contributions, the relative abundance of the highest concentration hopane monomer in house dust was compared to that in outdoor air. Geographic variables related to TRAP emissions and outdoor NO2 concentrations from city-specific TRAP land use regression (LUR) models were calculated at each georeferenced residence location and assessed as predictors of variability in dust hopanes.
Hopanes relative abundance in house dust and ambient air were significantly correlated (Pearson’s r=0.48, p<0.05), suggesting that dust hopanes likely result from traffic emissions. The proportion of variance in dust hopanes concentrations explained by LUR NO2 was less than 10% in Vancouver, Winnipeg and Toronto while the correlations in Edmonton and Windsor explained 20 to 40% of the variance. Modeling with household factors such as air conditioning and shoe removal along with geographic predictors related to TRAP generally increased the proportion of explained variability (10-80%) in measured indoor hopanes dust levels.
Hopanes can consistently be detected in house dust and may be a useful tracer of TRAP exposure if determinants of their spatiotemporal variability are well-characterized, and when home-specific factors are considered.
Air pollution; Dust; Exposure assessment; Hopanes; Land use regression; Traffic
Multiple studies have demonstrated that early-life exposure to pets or siblings affords protection against allergic disease; these associations are commonly attributed to the “hygiene hypothesis”. Recently, low diversity of the infant gut microbiota has also been linked to allergic disease. In this study, we characterize the infant gut microbiota in relation to pets and siblings.
The study population comprised a small sub-sample of 24 healthy, full term infants from the Canadian Healthy Infant Longitudinal Development (CHILD) birth cohort. Mothers reported on household pets and siblings. Fecal samples were collected at 4 months of age, and microbiota composition was characterized by high-throughput signature gene sequencing.
Microbiota richness and diversity tended to be increased in infants living with pets, whereas these measures were decreased in infants with older siblings. Infants living with pets exhibited under-representation of Bifidobacteriaceae and over-representation of Peptostreptococcaceae; infants with older siblings exhibited under-representation of Peptostreptococcaceae.
This study provides new evidence that exposure to pets and siblings may influence the early development of the gut microbiota, with potential implications for allergic disease. These two traditionally protective “hygiene hypothesis” factors appear to differentially impact gut microbiota composition and diversity, calling into question the clinical significance of these measures. Further research is required to confirm and expand these findings.
Infants; Gut microbiota; Gut microbiome; Hygiene hypothesis; Microflora hypothesis; Pets; Siblings; Atopy; Allergic disease; Environmental exposures
The gut microbiota is essential to human health throughout life, yet the acquisition and development of this microbial community during infancy remains poorly understood. Meanwhile, there is increasing concern over rising rates of cesarean delivery and insufficient exclusive breastfeeding of infants in developed countries. In this article, we characterize the gut microbiota of healthy Canadian infants and describe the influence of cesarean delivery and formula feeding.
We included a subset of 24 term infants from the Canadian Healthy Infant Longitudinal Development (CHILD) birth cohort. Mode of delivery was obtained from medical records, and mothers were asked to report on infant diet and medication use. Fecal samples were collected at 4 months of age, and we characterized the microbiota composition using high-throughput DNA sequencing.
We observed high variability in the profiles of fecal microbiota among the infants. The profiles were generally dominated by Actinobacteria (mainly the genus Bifidobacterium) and Firmicutes (with diverse representation from numerous genera). Compared with breastfed infants, formula-fed infants had increased richness of species, with overrepresentation of Clostridium difficile. Escherichia–Shigella and Bacteroides species were underrepresented in infants born by cesarean delivery. Infants born by elective cesarean delivery had particularly low bacterial richness and diversity.
These findings advance our understanding of the gut microbiota in healthy infants. They also provide new evidence for the effects of delivery mode and infant diet as determinants of this essential microbial community in early life.
Chronic obstructive pulmonary disease (COPD) accounts for nearly three million deaths annually, with approximately 5% of deaths in Canada attributed to COPD in 2004. Mortality rates among individuals with COPD or asthma, however, are not extensively studied in North America. Certainly, follow-up of individuals with respiratory diseases can shed light on mortality risks and contribute valuable information to prevent premature death. Accordingly, this retrospective study investigated mortality rates and examined risk factors for premature death among patients diagnosed with respiratory diseases identified from two lung function testing databases of two respiratory clinics in Ontario during the 1990s.
Chronic obstructive pulmonary disease (COPD) and asthma are common; however, mortality rates among individuals with these diseases are not well studied in North America.
To investigate mortality rates and risk factors for premature death among subjects with COPD.
Subjects were identified from the lung function testing databases of two academic respiratory disease clinics in Hamilton and Toronto, Ontario. Mortality was ascertained by linkage to the Ontario mortality registry between 1992 and 2002, inclusive. Standardized mortality ratios were computed. Poisson regression of standardized mortality ratios and proportional hazards regression were performed to examine the multivariate effect of risk factors on the standardized mortality ratios and mortality hazards.
Compared with the Ontario population, all-cause mortality was approximately doubled among subjects with COPD, but was lower than expected among subjects with asthma. The risk of mortality in patients with COPD was related to cigarette smoking, to the presence of comorbid conditons of ischemic heart disease and diabetes, and to Global initiative for chronic Obstructive Lung Disease severity scores. Individuals living closer to traffic sources showed an elevated risk of death compared with those who lived further away from traffic sources.
Mortality rates among subjects diagnosed with COPD were substantially elevated. There were several deaths attributed to asthma among subjects in the present study; however, overall, patients with asthma demonstrated lower mortality rates than the general population. Subjects with COPD need to be managed with attention devoted to both their respiratory disorders and related comorbidities.
Asthma; Cohort study; COPD; Mortality; Risk factors
The environment is suspected to play an important role in the development of childhood asthma. Cohort studies are a powerful observational design for studying exposure–response relationships, but their power depends in part upon the accuracy of the exposure assessment.
The purpose of this paper is to summarize and discuss issues that make accurate exposure assessment a challenge and to suggest strategies for improving exposure assessment in longitudinal cohort studies of childhood asthma and allergies.
Exposures of interest need to be prioritized, because a single study cannot measure all potentially relevant exposures. Hypotheses need to be based on proposed mechanisms, critical time windows for effects, prior knowledge of physical, physiologic, and immunologic development, as well as genetic pathways potentially influenced by the exposures. Modifiable exposures are most important from the public health perspective. Given the interest in evaluating gene–environment interactions, large cohort sizes are required, and planning for data pooling across independent studies is critical. Collection of additional samples, possibly through subject participation, will permit secondary analyses. Models combining air quality, environmental, and dose data provide exposure estimates across large cohorts but can still be improved.
Exposure is best characterized through a combination of information sources. Improving exposure assessment is critical for reducing measurement error and increasing power, which increase confidence in characterization of children at risk, leading to improved health outcomes.
childhood asthma; cohort studies; exposure assessment
Adjusting medication for uncontrolled asthma involves selecting one of several options from the same or a higher treatment step outlined in asthma guidelines. We examined the relative benefit of introducing budesonide/formoterol (BUD/FORM) maintenance and reliever therapy (Symbicort SMART® Turbuhaler®) in patients previously prescribed treatments from Global Initiative for Asthma (GINA) Steps 2, 3 or 4.
This is a post hoc analysis of the results of five large clinical trials (>12000 patients) comparing BUD/FORM maintenance and reliever therapy with other treatments categorised by treatment step at study entry. Both current clinical asthma control during the last week of treatment and exacerbations during the study were examined.
At each GINA treatment step, the proportion of patients achieving target levels of current clinical control were similar or higher with BUD/FORM maintenance and reliever therapy compared with the same or a higher fixed maintenance dose of inhaled corticosteroid/long-acting β2-agonist (ICS/LABA) (plus short-acting β2-agonist [SABA] as reliever), and rates of exacerbations were lower at all treatment steps in BUD/FORM maintenance and reliever therapy versus same maintenance dose ICS/LABA (P < 0.01) and at treatment Step 4 versus higher maintenance dose ICS/LABA (P < 0.001). BUD/FORM maintenance and reliever therapy also achieved significantly higher rates of current clinical control and significantly lower exacerbation rates at most treatment steps compared with a higher maintenance dose ICS + SABA (Steps 2-4 for control and Steps 3 and 4 for exacerbations). With all treatments, the proportion of patients achieving current clinical control was lower with increasing treatment steps.
BUD/FORM maintenance and reliever therapy may be a preferable option for patients on Steps 2 to 4 of asthma guidelines requiring a more effective treatment and, compared with other fixed dose alternatives, is most effective in the higher treatment steps.
Chronic exposure to traffic-related air pollution (TRAP) may contribute to premature mortality, but few studies to date have addressed this topic.
In this study we assessed the association between TRAP and mortality in Toronto, Ontario, Canada.
We collected nitrogen dioxide samples over two seasons using duplicate two-sided Ogawa passive diffusion samplers at 143 locations across Toronto. We calibrated land use regressions to predict NO2 exposure on a fine scale within Toronto. We used interpolations to predict levels of particulate matter with aerodynamic diameter ≤ 2.5 μm (PM2.5) and ozone levels. We assigned predicted pollution exposures to 2,360 subjects from a respiratory clinic, and abstracted health data on these subjects from medical billings, lung function tests, and diagnoses by pulmonologists. We tracked mortality between 1992 and 2002. We used standard and multilevel Cox proportional hazard models to test associations between air pollution and mortality.
After controlling for age, sex, lung function, obesity, smoking, and neighborhood deprivation, we observed a 17% increase in all-cause mortality and a 40% increase in circulatory mortality from an exposure contrast across the interquartile range of 4 ppb NO2. We observed no significant associations with other pollutants.
Exposure to TRAP was significantly associated with increased all-cause and circulatory mortality in this cohort. A high prevalence of cardiopulmonary disease in the cohort probably limits inference of the findings to populations with a substantial proportion of susceptible individuals.
air pollution; GIS; mortality; nitrogen dioxide; traffic air pollution; Toronto
Variations in air pollution exposure within a community may be associated with asthma prevalence. However, studies conducted to date have produced inconsistent results, possibly due to errors in measurement of the exposures.
A standardized asthma survey was administered to children in grades one and eight in Hamilton, Canada, in 1994–95 (N ~1467). Exposure to air pollution was estimated in four ways: (1) distance from roadways; (2) interpolated surfaces for ozone, sulfur dioxide, particulate matter and nitrous oxides from seven to nine governmental monitoring stations; (3) a kriged nitrogen dioxide (NO2) surface based on a network of 100 passive NO2 monitors; and (4) a land use regression (LUR) model derived from the same monitoring network. Logistic regressions were used to test associations between asthma and air pollution, controlling for variables including neighbourhood income, dwelling value, state of housing, a deprivation index and smoking.
There were no significant associations between any of the exposure estimates and asthma in the whole population, but large effects were detected the subgroup of children without hayfever (predominately in girls). The most robust effects were observed for the association of asthma without hayfever and NO2LUR OR = 1.86 (95%CI, 1.59–2.16) in all girls and OR = 2.98 (95%CI, 0.98–9.06) for older girls, over an interquartile range increase and controlling for confounders.
Our findings indicate that traffic-related pollutants, such as NO2, are associated with asthma without overt evidence of other atopic disorders among female children living in a medium-sized Canadian city. The effects were sensitive to the method of exposure estimation. More refined exposure models produced the most robust associations.
Studies of the prevalence of asthma among migrating populations may help in identifying environmental risk factors.
We analyzed data from Vancouver, Canada, and from Guangzhou, Beijing and Hong Kong, China, collected during phase 3 of the International Study of Asthma and Allergies in Childhood. We subdivided the Vancouver adolescents according to whether they were Chinese immigrants to Canada, Canadian-born Chinese or Canadian-born non-Chinese. We compared the prevalence of asthma and wheezing among Chinese adolescents born in Canada, Chinese adolescents who had immigrated to Canada and Chinese adolescents living in China.
Of 7794 Chinese adolescents who met the inclusion criteria, 3058 were from Guangzhou, 2824 were from Beijing, and 1912 were from Hong Kong. Of 2235 adolescents in Vancouver, Canada, 475 were Chinese immigrants, 617 were Canadian-born Chinese, and 1143 were Canadian-born non-Chinese. The prevalence of current wheezing among boys ranged from 5.9% in Guangzhou to 11.2% in Canadian-born Chinese adolescents. For girls, the range was 4.3% in Guangzhou to 9.8% in Canadian-born Chinese adolescents. The prevalence of ever having had asthma ranged from 6.6% to 16.6% for boys and from 2.9% to 15.0% for girls. Prevalence gradients persisted after adjustment for other environmental variables (odds ratios for ever having had asthma among Canadian-born Chinese compared with native Chinese in Guangzhou: 2.72 [95% confidence interval 1.75–4.23] for boys and 5.50 [95% confidence interval 3.21–9.44] for girls; p < 0.001 for both). Among Chinese adolescents living in Vancouver, the prevalence of ever wheezing increased with duration of residence, from 14.5% among those living in Canada for less than 7 years to 20.9% among those living their entire life in Canada. The same pattern was observed for the prevalence of ever having had asthma, from 7.7% to 15.9%.
Asthma symptoms in Chinese adolescents were lowest among residents of mainland China, were greater for those in Hong Kong and those who had immigrated to Canada, and were highest among those born in Canada. These findings suggest that environmental factors and duration of exposure influence asthma prevalence.
To compare the cost-effectiveness of budesonide-formoterol in a single inhaler used as both maintenance and reliever medication versus clinician-directed titration of salmeterol-fluticasone as maintenance medication, plus salbutamol taken as needed, in controlling asthma in adults and adolescents.
A Canadian economic evaluation was conducted based on the results of a large (n=2143), open-label, randomized, controlled effectiveness trial in which health resource use was prospectively collected. The primary outcome measurement was the time to the first severe exacerbation. Costs included direct medical costs (physician and emergency room visits, hospitalizations, asthma drug costs, etc) and productivity (absenteeism). The time horizon was one year, which corresponded to the duration of the clinical trial. Prices were obtained from 2005 Canadian sources. Both health care and societal perspectives were considered, and deterministic univariate sensitivity analyses were conducted.
In the clinical trial, budesonide-formoterol as maintenance and reliever treatment was superior to salmeterol-fluticasone with respect to the time to the first severe exacerbation, overall rate of exacerbations and use of as-needed reliever medication. The annualized rate of severe exacerbations was 0.24 events/patient in the budesonide-formoterol arm and 0.31 events/patient in the salmeterol-fluticasone arm (P=0.0025). From a health care perspective, the mean cost per patient-year was $1,315 in the budesonide-formoterol arm versus $1,541 in the salmeterol-fluticasone arm. From a societal perspective, the mean cost per patient-year was $1,538 in the budesonide-formoterol arm and $1,854 in the salmeterol-fluticasone arm. Budesonide-formoterol was dominant (more effective and less expensive) in the base case analysis from both perspectives. The results were robust under sensitivity testing.
The strategy that allows budesonide-formoterol to be used in a single inhaler as both maintenance and reliever medication proved to be more effective and less expensive than a strategy of clinician-directed titration of salmeterol-fluticasone with salbutamol as reliever therapy.
Asthma; Budesonide-formoterol; Comparison; Economic evaluation; Salmeterol-fluticasone
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.
The sample (n=2962) was drawn from six Canadian sites.
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.
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.
Smoking and asthma, jointly and individually, are major determinants of obstructive disorders in young adults. Bronchial hyper-responsiveness contributes to obstruction in both groups.
Airway obstruction; Obstructive lung disease; Risk factors; Young adults