We aimed to investigate the potential causal associations of adiposity with asthma overall, asthma by atopic status or by levels of symptom control in a large adult population and stratified by sex. We also investigated the potential for reverse causation between asthma and risk of adiposity.
We performed a bidirectional one-sample Mendelian randomisation (MR) study using the Norwegian Nord-Trøndelag Health Study population including 56 105 adults. 73 and 47 genetic variants were included as instrumental variables for body mass index (BMI) and waist-to-hip ratio (WHR), respectively. Asthma was defined as ever asthma, doctor-diagnosed asthma and doctor-diagnosed active asthma, and was further classified by atopic status or levels of symptom control. Causal OR was calculated with the Wald method.
The ORs per 1 SD (4.1 kg/m2) increase in genetically determined BMI were ranged from 1.36 to 1.49 for the three asthma definitions and similar for women and men. The corresponding ORs for non-atopic asthma (range 1.42-1.72) appeared stronger than those for the atopic asthma (range 1.18-1.26), but they were similar for controlled versus partly controlled doctor-diagnosed active asthma (1.43 vs 1.44). There was no clear association between genetically predicted WHR and asthma risk or between genetically predicted asthma and the adiposity markers.
Our MR study provided evidence of a causal association of BMI with asthma in adults, particularly with non-atopic asthma. There was no clear evidence of a causal link between WHR and asthma or of reverse causation.
The influence of air pollution on disability days in Toronto during the period 1994-1999 was examined using data from Canada's National Population Health Survey. A model of disability days (the sum of days spent in bed and days when the respondent cut down on usual activities) during the 2 weeks prior to the interview was constructed by sequentially examining the influence of time period, personal characteristics, weather, and air pollution. After adjusting for these other factors, only the effects of carbon monoxide and particulate matter of median diameter less than 2.5 microm (PM2.5) were statistically significant (respectively, 30.8% (95% CI 1.2-69.0) and 21.9% (95% CI 3.8-43.0) increase in disability days for a change in concentration equal to the interquartile range of the 2-week average pollutant concentration). PM2.5 was more strongly associated with disability days in the warm season. Results of multipollutant models were difficult to interpret in that effect sizes appeared to be influenced by covariation among pollutants. With the exception of warm season results for PM2.5, findings were not sensitive to alternative analytical approaches. While these results are suggestive of significant effects of the urban air pollution mix at relatively low ambient concentrations, the precise contribution of individual pollutants could not be determined.
This article provides (1) a synthesis of the literature on the linkages between air pollution and human health, (2) an overview of quality management approaches in Canada, the United States, and the European Union (EU), and (3) future directions for air quality research. Numerous studies examining short-term effects of air pollution show significant associations between ambient levels of particulate matter (PM) and other air pollutants and increases in premature mortality and hospitalizations for cardiovascular and respiratory illnesses. Several well-designed epidemiological studies confirmed the adverse long-term effects of PM on both mortality and morbidity. Epidemiological studies also document significant associations between ozone (O3), sulfur (SO2), and nitrogen oxides (NO(x)) and adverse health outcomes; however, the effects of gaseous pollutants are less well documented. Subpopulations that are more susceptible to air pollution include children, the elderly, those with cardiorespiratory disease, and socioeconomically deprived individuals. Canada-wide standards for ambient air concentrations of PM2.5 and O3 were set in 2000, providing air quality targets to be achieved by 2010. In the United States, the Clean Air Act provides the framework for the establishment and review of National Ambient Air Quality Standards for criteria air pollutants and the establishment of emissions standards for hazardous air pollutants. The 1996 European Union's enactment of the Framework Directive for Air Quality established the process for setting Europe-wide limit values for a series of pollutants. The Clean Air for Europe program was established by the European Union to review existing limit values, emission ceilings, and abatement protocols, as set out in the current legislation. These initiatives serve as the legislative framework for air quality management in North America and Europe.
Evidence and Risk Assessment Division, Centre for Chronic Disease Prevention and Control, Public Health Agency of Canada, 120 Colonnade Road, AL 6701A, Ottawa, Ontario, Canada. Jinfu_Hu@phac-aspc.gc.ca
Epidemiologic studies have reported that moderate alcohol consumption is inversely associated with the risk of renal cell carcinoma (RCC), but sex-specific results are inconsistent. The present study examines the association between alcohol intake and the risk of RCC among men and women.
Mailed questionnaires were completed by 1138 newly diagnosed, histologically confirmed RCC cases and 5039 population controls between 1994 and 1997 in eight Canadian provinces. A food frequency questionnaire provided data on eating habits and alcohol consumption 2 years before data collection. Other information included socio-economic status, lifestyle habits, alcohol use, and diet. Odds ratios (ORs) and 95% confidence intervals (CIs) were derived through unconditional logistic regression.
Total alcohol intake was inversely associated with RCC in men and in women; the OR for the highest intake group (> or =22.3 g/day among men and > or =7.9 g/day among women) versus the non-drinkers was 0.7 (95% CI, 0.5-0.9) for both sexes. Analysis of menopausal status produced ORs for the highest intake group versus the non-drinkers of 1.2 (95% CI, 0.7-2.1) among premenopausal women and 0.6 (95% CI, 0.4-0.9) among postmenopausal women. Smoking and obesity were not important effect modifiers.
Moderate alcohol consumption may be associated with a decreased risk of RCC in men and in women (mainly postmenopausal women).
Recurrent events, such as repeated hospital admissions for the same health outcome, occur frequently in environmental health studies. In this study, we conducted an analysis of data on repeated respiratory hospitalizations among the elderly in Vancouver, Canada, for the period of June 1, 1995, to March 31, 1999, using a new method proposed by (Dewanji and Moolgavkar 2000, 2002) for recurrent events, and compared it with some traditional methods. In particular, we assessed the impact of ambient gaseous (SO2, NO2, CO, and O3) and particulate pollutants (PM10, PM2.5, and PM10-2.5) as well as the coefficient of haze (CoH) on recurrent respiratory hospital admissions. Using the new procedure, significant associations were found between admissions and 3-day, 5-day, and 7-day moving averages of the ambient SO2 concentrations, with the strongest association observed at the 7-day lag (RR = 1.044, 95% CI: 1.018-1.070). We also found PM10-2.5 for 3-day and 5-day lag to be significant, with the strongest association at 5-day lag (RR = 1.020, 95% CI: 1.001-1.039). No significant associations with admission were found with current day exposure.
T-lymphocytes may preferentially differentiate towards a Th1 subtype, which is thought to be involved in the autoimmune aspects of diabetes, or a Th2 subtype, which is thought to mediate allergic disease. The activation of one subtype is thought to inhibit the other. To determine if diabetes is less common among those with allergic disease, consistent with the postulated TH1/Th2 paradigm, we used data from the 2000-2001 Canadian Community Health Survey of those at least 12 years of age from 125,159 households. Diabetes requiring insulin was reported in 1% whether or not allergies were reported. The crude odds ratio between diabetes and allergies for the entire population was 1.06 (95% confidence interval (CI): 0.90, 1.24). Adjusted for household size, number of bedrooms, immigrant status, income adequacy, educational level, smoking status, alcohol drinking status, regular exercise, and age, there was a positive association between allergy and diabetes with an odds ratio of 1.25 (95% CI: 1.06, 1.49). These results do not provide evidence for the existence of the Th1/Th2 paradigm as a determinant of disease patterns in the general population.
Antagonism between Th1 and Th2 lymphocyte mediated responses has been proposed to explain the observed 20th Century population increase in Th2 mediated allergic disease and reciprocal decrease in infectious disease, which stimulates a Th1 mediated response.
To determine if Th1/Th2 antagonism would be consistent with associations between non-infectious diseases, we tested the hypothesis that the population prevalence of Th2 mediated allergies is inversely related to the prevalence of Th1 mediated rheumatoid arthritis.
The analysis was based on data from the Canadian Community Health Survey conducted by Statistics Canada in 2000-2001 of those at least 12 years of age from 125,129 households. Each subject was asked if he or she had certain chronic health conditions that had been diagnosed by a health professional. Logistic regression models were used to evaluate the association between rheumatoid arthritis and allergies with consideration of other important variables.
Allergy history was positively related to the prevalence of rheumatoid arthritis both in women (adjusted odds ratio (OR): 1.57, 95% CI: 1.43, 1.73) and in men (adjusted OR: 1.55, 95% CI: 1.36, 1.77).
The reported population prevalences of allergies and rheumatoid arthritis were positively associated and not explained by Th1/Th2 anatagonism suggesting that this mechanism may only be applicable to the association between an infectious and an immunologic disease. Mechanisms accounting for positive associations between immunologic diseases deserve further study.
McLaughlin Centre for Population Health Risk Assessment, Institute of Population Health, and Department of Epidemiology and Community Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada. Sliu@uottawa.ca
The association between ambient air pollution and adverse health effects, such as emergency room visits, hospitalizations, and mortality from respiratory and cardiovascular diseases, has been studied extensively in many countries, including Canada. Recently, studies conducted in China, the Czech Republic, and the United States have related ambient air pollution to adverse pregnancy outcomes. In this study, we examined association between preterm birth, low birth weight, and intrauterine growth retardation (IUGR) among singleton live births and ambient concentrations of sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone in Vancouver, Canada, for 1985-1998. Multiple logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for such effects. Low birth weight was associated with exposure to SO2 during the first month of pregnancy (OR = 1.11, 95% CI, 1.01-1.22, for a 5.0 ppb increase). Preterm birth was associated with exposure to SO2 (OR = 1.09, 95% CI, 1.01-1.19, for a 5.0 ppb increase) and to CO (OR = 1.08, 95% CI, 1.01-1.15, for a 1.0 ppm increase) during the last month of pregnancy. IUGR was associated with exposure to SO2 (OR = 1.07, 95% CI, 1.01-1.13, for a 5.0 ppb increase), to NO2 (OR = 1.05, 95% CI, 1.01-1.10, for a 10.0 ppb increase), and to CO (OR = 1.06, 95% CI, 1.01-1.10, for a 1.0 ppm increase) during the first month of pregnancy. In conclusion, relatively low concentrations of gaseous air pollutants are associated with adverse effects on birth outcomes in populations experiencing diverse air pollution profiles.
This study aimed to determine the association between home and vehicle exposure to environmental tobacco smoke (ETS), and chronic bronchitis based on data from 64,961 non-smokers aged 12 years and older who participated in the 2005 Canadian Community Health Survey (CCHS). The proportion of respondents who reported ETS exposure in the home and vehicle was 9.0% and 8.4% respectively. The prevalence of self-reported doctor diagnosed chronic bronchitis was 1.5%. When considered separately, home and vehicle ETS were both significantly associated with chronic bronchitis in children and adolescents aged 12-19 years, with adjusted odds ratios of 2.30 (95% CI 1.46-3.63) and 2.25 (95% CI 1.42-3.58), respectively. Neither home, nor vehicle ETS exposure was significantly associated with chronic bronchitis in age groups greater than 19 years. When home and vehicle ETS exposure were considered together, and sex, age, allergies, asthma, marital status, level of education, and race where controlled for, home ETS exposure was not a significant predictor of chronic bronchitis (P = 0.296), while vehicle ETS was. The correlation between exposure variables was fair, with a kappa coefficient of 0.40 (P
Obesity has been linked to stress, but there is lack of strong evidence from general populations.
The analysis was based on data from 112,716 Canadians aged 18 years or more who participated in a national survey conducted in 2007-2008. A questionnaire covered the information on self-perceived lifetime stress, height, and weight. Logistic regression analysis was used to determine the association between chronic stress and obesity.
The crude prevalence of obesity was 18.1% for men and 16.0% for women. A small proportion (3.7%) of the participants reported being extremely stressed most days in their lives and 19.1% reported being quite a bit stressed, and the proportions of stress were slightly higher in women than in men. Overall, those who reported being extremely stressed (adjusted OR: 1.23, 95% CI: 1.13, 1.35) or those who reported being quite a bit stressed (adjusted OR: 1.08, 95% CI: 1.02, 1.15) had an increased risk of obesity compared with who were not at all stressed. The adjusted odds ratio was 1.44 (95% CI: 1.13, 1.35) for women who were extremely stressed compared with women who were not at all stressed.
Lifetime stress was associated with an increased risk of obesity especially in women.