Associations between physical activity and constipation in adult Americans: Results from the National Health and Nutrition Examination Survey

Background There is mixed evidence that physical activity is associated with constipation on the population level. This analysis aimed to determine whether amount and types of physical activity are cross-sectionally associated with constipation. Methods A total of 9963 adults from the 2007-2010 National Health and Nutrition Examination Survey (NHANES) were included. Constipation was defined based on low stool frequency (<3 stools/wk) and a hard/lumpy consistency (type 1 or 2 on the Bristol Stool Form Scale). Univariate logistic regression models evaluated associations between physical activity variables and constipation, while multivariate models were built to account for other variables (age, gender, education, race/ethnicity, relationship status, health status, body mass index, fiber intake, and moisture intake). Key results Based on <3 stools/wk, 3.4% (95% CI, 2.8%-4.2%) of Americans were constipated, whereas 7.3% (95% CI, 6.7%-8.1%) were deemed constipated when using the hard/lumpy definition. Odds ratios (ORs) of experiencing < 3 stools/wk were 1.82 (95% CI, 1.11-2.97) for people engaging in no vigorous recreational activity (vs. any) and 1.41 (95% CI, 1.08-1.85) for those doing no moderate recreational activity (vs. any). Likewise, doing no moderate recreational activity was associated with slightly higher odds of hard/lumpy stools (OR = 1.23, 95% CI, 1.03-1.46). These associations were attenuated and insignificant in multivariate models (all ORs < 1.45). Conclusion On the population level, self-reported physical inactivity is not strongly associated with passing < 3 stools/wk or hard/lumpy stools. Better-designed prospective observational and intervention studies are needed to clarify how physical inactivity impacts different forms of constipation.