Dynamic patterns of body size and mortality among older adults in China: Evidence from a multi-city cohort study

Changes in body size in later life may influence survival, yet evidence on how changes in BMI, weight and waist circumference relate to mortality in older adults remains limited. Using data from 1,412,411 adults aged 65 years and older in a nationwide Chinese cohort with repeated examinations from 2017 to 2023, we primarily evaluated BMI transition patterns in relation to all-cause and cause-specific mortality, with relative and absolute body size changes examined as complementary measures. The primary Cox analyses, incorporating the Stable Cox procedure, included 1,338,732 participants with complete covariate data. Compared with remaining normal weight, persistent underweight (HR = 1.61 [95% CI, 1.56 to 1.66]) and transition from normal weight to underweight (HR = 1.46 [1.42 to 1.50]) were associated with higher mortality, whereas remaining overweight (HR = 0.77 [0.75 to 0.79]) and transition from normal weight to overweight (HR = 0.75 [0.73 to 0.77]) were associated with lower mortality. Analyses of relative and absolute changes broadly supported the BMI transition findings. Associations were broadly consistent across gender, age, and causes of death. Declining body size measures in later life may serve as markers of health deterioration and help identify older adults who warrant further clinical assessment.