Age at diagnosis, lifestyle factors, and risk of mortality: a city-wide cohort study of cancer survivors

Background The growing global cancer burden highlights the urgent need to improve long-term outcomes among cancer survivors. Age-related biological changes may modify the associations between lifestyle factors and mortality, yet the joint effects of diagnostic age and lifestyle factors remain poorly understood. Methods Cancer survivors diagnosed between 2010 and 2018 in Guangzhou were followed up until 2023. Associations of lifestyle factors with all-cause mortality risk were examined, stratified by early-onset (< 50 years) and late-onset (≥ 50 years) cancers. Interactions were evaluated on multiplicative and additive scales. Results Among 22,079 cancer survivors, 10,839 deaths occurred during a median follow-up of 4.14 years. An antagonistic interaction of diagnostic age with physical activity on all-cause mortality risk was observed. Compared with inactivity, physical activity (≥ 150 min/week) was associated with a 15% lower risk of all-cause mortality (restricted mean survival time [RMST] difference: 0.29 years) in early-onset survivors and a 23% lower risk in late-onset survivors (RMST difference: 0.69 years). A synergistic interaction of diagnostic age with sleep duration was observed. Compared with 7 h/day, short sleep duration (≤ 5 h/day) was associated with a higher mortality risk (RMST difference: −0.43 years) in early-onset survivors, while 8 h/day was associated with a lower risk in late-onset survivors (RMST difference: 0.13 years). Conclusions Sufficient physical activity and sleep duration were significantly associated with improved survival, with their effects varying by diagnostic age. These findings underscore the importance of tailored lifestyle management strategies for early-/late-onset cancer survivors to mitigate mortality burden.