Associations of Body Mass Index and Waist Circumference with Falls among Community-Dwelling Older Adults in Korea

Objectives: This study aimed to investigate the association between obesity and falls among community-dwelling older adults in Korea and to assess whether body mass index (BMI) or waist circumference (WC) more accurately predicts fall risk. Methods: This study included 4,378 community-dwelling older adults aged ≥65 years from the seventh Korea National Health and Nutrition Examination Survey (2016-2018). Complex-sample logistic regression analyses were conducted to examine the associations between general and central obesity and falls, stratified by sex and age group. Predictive accuracy was evaluated using Harrell's C-index, and differences between WC and BMI were assessed using the ΔC-index and the DeLong test. Results: BMI-defined general obesity was not significantly associated with falls. In contrast, WC-defined central obesity was significantly associated with falls among older adults overall (adjusted odds ratio = 1.82, 95% CI: 1.20-2.76). In sex-stratified analyses, central obesity remained significantly associated with falls in both men and women. Age-stratified analyses showed a significant association between central obesity and falls among adults aged 65-74 years, but not among those aged ≥75 years. WC demonstrated a modest but statistically significant improvement in predictive ability compared with BMI (ΔC-index = 0.047, p = 0.044), although subgroup differences were not statistically significant. Conclusions: Central obesity, but not general obesity defined by BMI, was significantly associated with falls among community-dwelling older Korean adults. WC showed slightly better predictive performance than BMI. These findings suggest that WC may be a more appropriate indicator than BMI for identifying older adults at increased risk of falls.