Associations of accelerometer-measured physical activity and physical activity-related cancer incidence in older women: results from the WHI OPACH Study

BACKGROUND: We examined the associations between accelerometry-measured physical activity (PA) and incidence of 13 cancers among a cohort of postmenopausal women. METHODS: In this prospective study, 6382 women wore ActiGraph GT3X+ accelerometers at the hip for up to 7 days during 2012–2013, and were followed over a median of 4.7 years for diagnosis of 13 invasive cancers. Calibrated intensity cut points were used to define minutes per day of total, light and moderate-to-vigorous PA. We used multivariable Cox regression to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for tertiles, and one-standard deviation (SD) unit increments of PA exposures in relation to cancer incidence. We examined effect measure modification by age, race/ethnicity, body mass index and smoking history. RESULTS: The highest (vs. lowest) tertiles of total, light and moderate-to-vigorous PA were associated with covariate-adjusted HRs of 0.72 (95% CI = 0.53–0.97), 0.81 (95% CI = 0.60–1.09) and 0.66 (95% CI = 0.48–0.91), respectively. In age-stratified analyses, HRs for total PA were lower among women <80 years (HR(per one-SD) = 0.75, 95% CI = 0.63–0.90) than among women ≥80 years (HR(per one-SD) = 0.99, 95% CI = 0.82–1.18) (P(Interaction) = 0.03). Race/ethnicity, BMI and smoking did not strongly modify these associations. CONCLUSIONS: Engaging in physical activity may play a beneficial role in the prevention of certain cancers in older women.