Physical activity and cancer risk: Findings from the UK Biobank, a large prospective cohort study

Objectives: This study aimed to investigate the association between physical activity and site-specific cancer incidence. Methods: UK Biobank is a prospective population-based cohort study. 364,899 adults (51.6 % females, mean age 56.0 years) were included. The exposure variable was physical activity level derived from the International Physical Activity Questionnaire-Short Form (IPAQ-SF). Participants were categorised at 'high' ( >= 1,500 MET-minutes/week), 'moderate' (>= 600 MET-minutes/week) or 'low' levels of activity following standardised IPAQ-SF scoring guidance. Primary outcome measures included incident cancers at 20 sites. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95 % confidence intervals (CIs) showing relationships between physical activity and cancer. Results: 21,816 incident cancers were identified. Significant associations were identified between high physical activity levels and lower risk of lung (HR 0.81, 95 % CI: 0.70, 0.94), breast (female only) (HR 0.85, 95 % CI: 0.77, 0.94), hepatobiliary tract (HR 0.72, 95 % CI: 0.53, 0.97), and colon (HR 0.86, 95 % CI: 0.74, 0.99) cancers compared to low physical activity levels. Moderate levels of physical activity were associated with significantly lower risk of oropharyngeal (HR 0.71, 95 % CI: 0.55, 0.93), and lung cancer (HR 0.86, 95 % CI: 0.74, 0.99) compared to low physical activity levels. Sensitivity analyses showed associations of higher physical activity with lower oesophageal and higher prostate cancer incidence. Conclusions: Regular physical activity is significantly associated with reduced risk for lung, breast, hepatobiliary tract, colon and oropharyngeal cancers. Our findings highlight the importance of physical activity promotion, particularly high levels of physical activity, in cancer prevention.