Synergistic Effects of Body Mass Index in Early Adulthood and Recent Weight Gain in Reducing Mortality Risk Among Cancer Survivors.

Background: Cancer survivors face an elevated risk of mortality, and changes in body mass index (BMI) may play a critical prognostic role. This study examined BMI variations during early adulthood and recent years in relation to cancer-specific mortality and all-cause mortality.

Methods: Data were drawn from the National Health and Nutrition Examination Survey. Statistical models were applied to evaluate associations, dose-response relationships, and threshold effects.

Results: Among 2,024 cancer survivors, recent BMI increases were significantly associated with reduced cancer and all-cause mortality, whereas earlier BMI changes showed weaker associations. Compared with those in the lowest tertile, those with greater recent BMI increases had a 24%-44% lower risk of cancer mortality (P for trend = 0.016) and a 34%-45% lower risk of all-cause mortality (P for trend < 0.001). A non-linear association was identified, with a 5% BMI increase as the threshold; each 1% gain below this threshold was linked to a 4% mortality risk reduction (p < 0.001). Joint analysis revealed that a high early BMI combined with a ≥ 5% recent BMI increase significantly reduced mortality risk.

Conclusions: Moderate recent weight gain may improve survival among cancer survivors, underscoring the importance of individualized weight management strategies.