Associations of device-measured physical activity and body mass index with cancer incidence: prospective cohort study

Background: Low physical activity (PA) and high adiposity are associated with cancer risk. It is unclear whether different amounts and intensities of PA can mitigate this association.

Purpose: We aimed to examine the joint dose-response associations between body mass index (BMI) and accelerometer-measured PA with incident cancer.

Methods: UK Biobank participants were classified as normal weight (18.5-24.9 kg/m2), overweight (25-29.9 kg/m2) or obese (>30 kg/m2) BMI. PA data included weekly light-intensity (LPA), moderate-to-vigorous-intensity (MVPA), vigorous-intensity (VPA), and total volume. Cancer diagnoses and deaths were obtained from registries. We excluded participants with events in the first two years of follow-up, prevalent diseases, or physical limitations. Hazard ratios were calculated from proportional sub-hazards models with multivariate adjustment and age as timescale to examine the joint dose-response associations between BMI categories and PA levels with incident fatal and non-fatal cancer, accounting for other deaths as competing events.

Results: Analysis included 70,747 participants (mean age 61.6 ± 7.9, 56.4% women) over a median 6.1-year follow-up, with 2,625 incident cancer cases. Compared with the referent (normal-weight and 5th centile of total PA/LPA and zero MVPA/VPA), participants with overweight and obesity showed a 25% to 45% higher cancer hazard at zero MVPA, VPA and low total PA levels. Some attenuation of these associations was found from MPVA levels within international guidelines, from VPA below the guidelines, and with higher total PA. Normal weight participants did not show a higher cancer hazard regardless of PA levels. No clear associations were found for LPA.

Conclusions: High levels of MVPA, VPA and total PA may attenuate but not clearly offset the cancer hazard associated with overweight and obesity. Maintaining a healthy weight seems comparatively more important.

Practical implications: Public health efforts should encourage both weight control and promoting higher PA to mitigate cancer risk effectively.

Funding: None