Changes in physical activity and diabetes risk after cancer diagnosis: a nationwide cohort study.

PURPOSE: Physical activity has the potential to reduce the risk of diabetes after cancer diagnosis. However, current evidence supporting its effects is limited. This study aims to examine the associations between changes in physical activity and subsequent risk of diabetes among cancer survivors.

METHODS: A total of 264,250 cancer survivors (mean age 56.7 (12.5) years, 44.2% males) without a prior history of diabetes were assessed for adherence to physical activity both before and after their diagnosis. The primary outcome was incident diabetes. The Fine-Gray proportional sub-distribution hazards model was used to calculate sub-distribution hazard ratios (sHRs) and 95% confidence intervals (CIs) for diabetes risk, considering death as a competing risk.

RESULTS: Over a follow-up of 1,065,802 person-years, maintaining regular physical activity from pre-diagnosis was associated with a 10% reduced risk of diabetes after cancer diagnosis (sHR 0.90, 95% CI 0.85-0.96), considering traditional diabetes risk factors, sociodemographics, and primary cancer sites. Cancer survivors who became active and inactive after their cancer diagnosis exhibited a marginally decreased risk of diabetes (sHR 0.98, 95% CI 0.93-1.03; sHR 0.97, 95% CI 0.92-1.03). The strength and direction of the association varied depending on the primary site of cancer.

CONCLUSIONS: Regular physical activity starting before a cancer diagnosis is associated with a lower risk of diabetes following the diagnosis, independent of established diabetes risk factors.

IMPLICATIONS FOR CANCER SURVIVORS: The study underscores the importance of engaging in sufficient physical activity to mitigate the risk of diabetes in cancer survivors.