Time-Varying Body Mass Index, Waist Circumference and All-Cause Mortality in US Adults Aged 65 or Older.

BACKGROUND: This study examined associations of body mass index (BMI) category and waist circumference (WC) independently and in tandem on all-cause mortality risk among US adults aged ≥ 65 years. METHODS: The present study utilized 14 years of longitudinal data (2011-2024) from 6905 participants in the National Health and Aging Trends Study. Cox proportional hazards models were used to estimate the hazard ratios (HRs), adjusted for baseline age, race, education, annual income, smoking status, and homebound status. RESULTS: Compared with normal weight, overweight males (HR, 0.54 [95% CI, 0.45-0.66]) and males with class I and II obesity (HR, 0.49 [95% CI, 0.37-0.65]) had lower mortality risk. High WC was associated with greater mortality risk in males (HR, 1.24 [95% CI, 1.07-1.44]). Similar patterns were observed in females. In joint BMI-WC analyses, overweight regardless of WC status and class I and II obesity with high WC were associated with lower mortality risk among males. Being underweight, regardless of WC status, and having normal weight with high WC were both associated with higher mortality risk in both sexes. CONCLUSIONS: These findings highlight the adverse association of central adiposity and the limitations of BMI-only classification for mortality risk stratification in older adults.