Bioimpedance-Estimated Metabolic Age in a Falls Clinic: Associations with Multimorbidity and Physical Frailty.

Bioelectrical impedance analysis (BIA) is a non-invasive method used to assess body composition and estimate metabolic age (MA). However, the clinical significance of BIA-estimated MA remains poorly understood. We explored the associations of MA with chronological age (CA), multimorbidity, and physical frailty (PF) in falls clinic attendees. Participants aged ≥50 years were assessed for multimorbidity using the Cumulative Illness Rating Scale-Geriatric, PF using the SHARE Frailty Instrument for Primary Care, and underwent BIA. Among 107 participants (mean age 69.8 years, 57% women), MA showed a moderate correlation with CA (=0.62, p<0.001). On bivariate analysis, participants with MA>CA were younger, had higher multimorbidity, and were frailer compared to those with MA<CA. Multivariate linear regression analyses revealed that MA was independently associated with CA and BIA-estimated fat mass in both sexes, BIA-estimated muscle mass in men, and PF in women, but not with multimorbidity. BIA-estimated MA mostly reflects CA and BIA's own body composition estimates, but was significantly associated with PF in women. Research should externally validate this finding and investigate the responsiveness of BIA-estimated MA to interventions.