| Summary: | Background and Rationale: Asthma and overweight are public health concerns. Lifestyle, including dietary and activity patterns, is associated with overweight and asthma. Moreover, an association between these two diseases has been described. Yet, few studies have considered these associations longitudinally in youth. Methods: Based on data from the 1995 Manitoba Birth Prospective Cohort (n=723, 404 [55.9%] boys), we designed a series of studies to address the question: “Do obesity and related lifestyle behaviours influence asthma and airway hyperresponsivess (AHR) outcomes in children?” Following protocol for a mixed methods sequential explanatory design study, we first considered this research question using quantitative methods. Exposure variables included weight status (body mass index (BMI); BMI z-scores; normal weight vs. overweight), diet, physical activity and screen time. Outcome variables included asthma and AHR at 8-10 years old and at 12-13 years old. Quantitative findings provided direction for the qualitative investigations. That is, we sought to further explain some of the quantitative findings using qualitative methods. For the qualitative portion of this dissertation, 15-16 year old youth were purposively selected (Winnipeg residency, asthma status, gender) from the 1995 Manitoba Prospective Birth Cohort. Due to recruitment challenges, participation was supplemented with youth from the Canadian Asthma Primary Prevention Study, using the same purposive selection criteria. Quantitative Results: Overweight at 12-13 years old was associated with a two-fold increased odds of persistent asthma in girls. In contrast, boys within the highest BMI quartile at 8-10 years old were nearly twice as likely to have remittent asthma at 12-13 years old. High vegetable intake was protective against allergic asthma and moderate-to-severe AHR by 50% and 42%, respectively. High screen time at 8-10 years old, particularly amongst overweight youth, was associated with an increased odds of asthma, but not AHR at 8-10 years and 12-13 years; there were no associations between physical activity, asthma and AHR. Qualitative Results: Youth spoke of asthma as a condition that neither limits physical activity, nor is an excuse for refraining from physical activity. Conclusions: Modest evidence that some quantitatively-measured weight and related lifestyle behaviours during the pubertal years is associated with asthma. Yet, qualitative data suggest that youth with asthma believe that physical activity is achievable despite their condition, although some describe that asthma interferes with physical activity.
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