Background: Physical activity during adulthood has been consistently associated with lower risk of colorectal cancers, but whether physical activity during adolescence may also play a role in colorectal carcinogenesis is unclear.
Methods: We included 28,250 women in the Nurses' Health Study II who provided data on physical activity during adolescence (ages 12-22 years) in 1997 and underwent lower bowel endoscopy (1998-2011). We used logistic regression models for clustered data to examine the association between physical activity during adolescence and risk of adenoma later in life.
Results: Physical activity during adolescence was inversely associated with risk of colorectal adenoma (2373 cases), independent of physical activity during adulthood. The multivariable-adjusted odds ratio (OR) of adenoma was 0.89 (95% CI 0.77-1.02; Ptrend = 0.03) comparing women with ≥ 72 metabolic equivalent of tasks-hours/week (MET-h/week) to < 21 MET-h/week. Women with high physical activity during both adolescence (≥53.3 MET-h/week) and adulthood (≥23.1 MET-h/week) had significantly lower risk of adenoma (all adenomas: OR 0.76; 95% CI 0.66-0.88; advanced adenoma: OR 0.61; 95% CI 0.45-0.82) compared to women with low physical activity during both stages of life.
Conclusions: Our findings suggest that physical activity during adolescence may lower the risk of colorectal adenoma later in life.