Optimal body composition indices cutoff values based on all-cause mortality in the elderly

The cutoffs of body composition indices are inconclusive in older populations. This study is designed toward determining the optimal cutoffs of the body composition indices based on the association with all-cause mortality. During 2009 and 2010, a cohort population of 1200 was enrolled in central western Taiwan. Of the 1200 subjects, 428 older subjects (mean age: 72.5 ± 5.4 yrs.; 47.7 % were women) were censored in this study. The waist circumference (WC) and body mass index (BMI) were measured using standard anthropometric methods. A multi-frequency bioelectrical impedance analysis device was utilized to estimate each participant's body composition indices, including percent body fat (PBF) and skeletal muscle mass index (SMMI). All claims records of death from 2009 to 2018 in the National Health Insurance Research Databank were identified. A receiver operating characteristic curve method and the highest Youden index were used to identify the optimal cutoffs. A Cox proportional hazards regression analysis was used to model associations between each of the recommended cutoff values with all-cause mortality. The all-cause mortality rate was 20.09 % after a follow-up period of 5.86 ± 2.39 person-years. The significant indices cutoff value was identified to be WC (86.7 cm) for older women and BMI (23.8 kg/m²) and as WC (77.6 cm), and SMMI (8.7 kg/m²) for older men. The recommended optimal cutoffs of the body composition indices were gender-specific and can be utilized to predict the risk of all-cause mortality.