Leisure-time energy expenditure in asthmatics and non-asthmatics.

An association between obesity and asthma has been documented previously, but the nature of this relationship remains unknown. This study aimed to determine if asthma is associated with a sedentary lifestyle which may explain this association. The energy expenditure (EE) on leisure activities was examined in 16,813 subjects, of at least 12 years of age, who participated in the Canadian National Population Health Survey 1994-95. Energy expenditure was calculated by multiplying the duration of leisure-time physical activity by its estimated metabolic energy cost. Asthma was considered to be present if an affirmative response was given to the question, 'Do you have asthma diagnosed by a health professional?' The average EE (+/- standard error) in males was 2.47 (+/- 0.11) kcal kg(-1) day(-1) for asthmatics and 1.98 (+/- 0.03) kcal kg(-1) day(-1) for non-asthmatics. The corresponding average EEs in females were 1.77 (+/- 0.08) and 1.54 (+/- 0.02) kcal kg(-1) day(-1) for asthmatics and non-asthmatics, respectively. The mean EE values decreased with increasing age. A significant interaction between asthma and age was noted with respect to EE; asthmatics tended to have higher mean EE values than non-asthmatics among younger subjects, and lower mean EE values in older subjects. This effect was more pronounced in females than in males. It was concluded that asthmatics were not consistently inactive compared with non-asthmatics. Leisure-time physical activity cannot explain the positive association between obesity and asthma.