A systematic review of the relationship between body composition including muscle, fat, bone, and body water and frailty in Asian residents.

International guidelines suggested that overweight and underweight are risk factors for frailty. However, body composition, which directly affects body weight, was not mentioned as a risk factor. We aimed to investigate whether the body composition, including muscle, fat, bone, and body water, is a risk factor for frailty. MEDLINE, Cumulative Index to Nursing and Allied Health Literature, and Scopus were searched up to June 03, 2022. We included cohort studies or observational studies using a cross-sectional design that reported an association between body composition and frailty. Two reviewers assessed the quality of the included cohort studies. Furthermore, we examined whether body composition as a risk factor for frailty varies depending on the participant's place of residence. Of the 3871 retrieved studies, 77 were ultimately included, 7 of which were cohort studies. The risk-of-bias evaluation in each cohort study showed that all studies had at least one concern. Low lean mass, waist circumference-defined abdominal obesity, and bone mineral density were significantly associated with frailty in the cohort studies. The results of bone mineral density were conflicted in the cross-sectional studies. Considering the participants' place of residence, a significant association between lower-extremity muscle mass and frailty was demonstrated, particularly among Asian residents. Low lean mass and abdominal obesity were likely risk factors for frailty. These results could be useful for developing frailty prevention strategies and could have a positive impact on individual health management. Further, future studies are needed because body composition affecting frailty may differ by race.