Overview of longitudinal studies on physical activity at baseline and incident asthma.

Overview of study characteristics, study quality based on the Newcastle-Ottawa Scale (NOS) and odds ratios of longitudinal studies on physical activity and asthma incidence. Note that Beckett and Lucke use high physical activity levels as reference category, while Benet, Huovinen and Thomsen use low physical activity levels as reference category.
CI; confidence interval, PA; physical activity, aHR; adjusted hazard ratio, aOR; adjusted odds ratio, OR; odds ratio.
*P<0.05.
#aData provided by the authors.
#bAnalyses did not account for the correlation between twin pairs but twins were considered unrelated subjects.
#cPA assessed through questionnaires using the Physical Activity History Score (validated); categorized in five equal levels (quintiles).
#dPA defined as time spent in household and leisure time PA, converted to metabolic equivalents (METs); categorized in three equal levels (tertiles).
#eThree categories of PA: Sedentary: Respondents estimating their own leisure time physical activity as practically non-existent. Conditioning: Respondents who exercised at least 6 times per month for at least 30 min with a mean intensity corresponding to walking. Occasional: Respondents who did not meet the criteria of sedentary or conditioning.
#fTwo categories of PA: Nil/low PA: <600 METs (metabolic equivalents) per week (this reflects 30 minutes of moderate activity on five days each week). Moderate/high PA: >600 METs per week.
#gTwo categories of PA: Low PA: <2 hours per week of light leisure time exercise activities. High PA: >2 hours per week of light leisure time exercise activities.
#hother confounders: age, race, centre, and maximal education.
#iother confounders: menopausal status, education level, working status, and co-morbidities.
#jother confounders: age, atopy, and respiratory symptoms.