Physical activity and constipation in Hong Kong adolescents.

Objective: To examine the association of constipation with exercise, non-exercise physical activity, and sedentary behaviours in Hong Kong adolescents.

Methods: In 2006-2007, 42 secondary schools were randomly selected to participate in the Hong Kong Student Obesity Surveillance (HKSOS) project. A total of 33692 Form 1-7 students (44.9% boys; mean age 14.8, SD 1.9 years) completed an anonymous questionnaire on lifestyle behaviours. Constipation was defined as a frequency of evacuation of less than once every two days. Exercise (moderate-to-vigorous levels) and non-exercise physical activity (NEPA) were each considered insufficient when less than 1 hour per day, and sedentary behaviours were considered excessive when over 4 hours per day. Logistic regression was used to calculate adjusted odds ratio (AOR) for constipation in relation to exercise, NEPA, and sedentary behaviours, adjusting for potential confounders.

Results: Constipation was identified in 15.6% (95% CI 15.2% - 16.0%) of adolescents overall, 14.0% in those with sufficient exercise and 19.6% in those without. Constipation was associated with insufficient exercise (AOR 1.26, 95% CI 1.16 - 1.36), insufficient NEPA 1.21 (1.10 - 1.33) and excessive sedentary behaviours (1.25, 1.17 - 1.34). Compared with having none of the above 3 inactive behaviours, increasing AORs of constipation were observed for having 1 (AOR 1.23), 2 (AOR 1.57) and 3 (AOR 1.88) inactive behaviours (p for trend <0.001).

Conclusions: Constipation was associated with insufficient physical activity and excessive sedentary behaviours among Chinese adolescents with a dose-response relation. If the association is causal, constipation could be prevented by promotion of physical activity.