Asthma prevalence has been reported to be lower in rural regions, but the reasons for this are not known.
To confirm the existence of an urban-rural geographic gradient in asthma prevalence among Canadian youths and to evaluate whether this gradient was mediated by health behaviors.
Cross-sectional data from 4,726 Canadian youth (grades 6-10) were collected during the 2001-02 Health Behaviour in School-Aged Children survey. Geographic region was categorized as metro (urbanized), non-metro but adjacent to metro, and rural. Asthma was defined via self-report of doctors' diagnoses and at least 1 of: (1) asthma symptoms or (2) a health care visit for asthma in the past year. Health behaviors (diet and physical activity) as well as obesity were also assessed.
Asthma prevalence was lowest in rural regions (metro = 17.7%, non-metro-adjacent = 15.6%, rural = 14.8%). A lower risk of asthma was associated with rural region (adjusted odds ratio [OR] = 0.76, 95% CI = 0.61-0.95) and living in non-metro-adjacent regions (adjusted OR = 0.81, 95% CI = 0.65-1.01). Health behaviors and obesity status did not mediate the association between geographic region and asthma. Being overweight or obese, having a high physical activity level, and exposure to passive smoking independently elevated the risk of asthma, whereas increased consumption of whole milk or vegetables were each protective.
Although asthma prevalence among youth was lower in rural areas, this association was not mediated by health behaviors or obesity. Other exposures, likely environmental, are the logical mechanisms through which rural geographic status is related to lower asthma prevalence.