A Body Shape Index (ABSI) Shows Stronger Associations with Falls than BMI Among Older Adults: Evidence from the NHATS Cohort

Introduction Falls are a major public health concern among older adults, leading to injuries, loss of independence, and increased mortality. A Body Shape Index (ABSI), which integrates waist circumference with height and weight, may better capture abdominal adiposity than BMI. To our knowledge, this is the first study to examine the association between ABSI and fall risk in older adults using data from the National Health and Aging Trends Study (NHATS). Methods We analyzed data from NHATS, a nationally representative cohort of U.S. Medicare beneficiaries aged ≥65 years. Baseline anthropometric data (height, weight, waist circumference) from Round 1 were linked to 12-month fall outcomes in Round 2. Exposures were BMI and ABSI. Survey-weighted logistic regression models estimated associations between each measure and fall outcomes, adjusting for sociodemographic and health-related covariates. Results In adjusted models, ABSI was significantly associated with both any fall (OR = 1.15, 95% CI 1.04–1.27; p = 0.009) and multiple falls (OR = 1.20, 95% CI 1.03–1.39; p = 0.018). BMI showed weaker and less consistent associations (any fall: OR = 1.02, 95% CI 1.00–1.03; p = 0.030; multiple falls: OR = 1.01, 95% CI 0.995–1.03; p = 0.158). Associations were stronger among adults aged ≥80 years and those with multimorbidity or conditions such as arthritis, hypertension, or diabetes. Conclusion ABSI may be a more sensitive anthropometric measure than BMI for identifying older adults at risk for falls, underscoring its potential to improve geriatric fall-risk assessment and prevention strategies.