Sex differences in association between body composition and frailty or physical performance in community-dwelling older adults

Frailty is a common geriatric condition due to aging, defined as a decrease in the functional reserve to maintain the homeostasis. As part of the aging process, body composition changes occur. This study investigated the relationship between body composition and frailty in a community-dwelling elderly Korean population. This cross-sectional cohort study analyzed data of 2,385 elderly participants (aged 70–84 years, 1131 males and 1254 females) of the Korean Frailty and Aging Cohort Study from 2016 to 2017. Body composition, including total and trunk fat masses and fat-free mass, were measured with dual-energy X-ray absorptiometry. Fat mass index (FMI), trunk fat mass index, and fat-free mass index (FFMI) represented total fat mass, trunk fat mass, and fat-free mass according to height. Based on the frailty index developed by Fried, we compared the frail and non-frail groups. Poor physical performance assessed with the short physical performance battery score of < 9 is considered frailty. To evaluate the relationship between the variables, simple and fully adjusted multivariable logistic regression analyses were performed according to sex. Among the participants, 462 (19.3%) were defined as the frail group, with a significantly high mean age of 77.9 ± 4.0 years. In the logistic regression analysis of frailty based on body mass index (BMI) categories, underweight (BMI < 18 kg/m(2)) participants showed a high incidence of frailty in both sexes. BMI showed an association with frailty only in males. Lower FFMI was associated with a higher incidence of frailty in both sexes, which was statistically significant in the fully adjusted models. In the female, fat-related indexes including body fat percentage, FMI, and trunk fat mass index showed a significant association with poor physical performance. In contrast, males with low FFMI only showed a significant association with poor physical performance. Frailty was closely correlated with lower FFMI in both sexes. The poor physical performance associated with frailty correlated with fat-related body composition in females and fat-free mass in males, owing to the difference in body composition between the sexes. In the assessment of frailty, body composition and sex-related differences should be analyzed.