Association of Serum β2-microglobulin Levels with Prevalent and Incident Physical Frailty in Community-Dwelling Older Women

Abstract

Physical frailty is common among older adults and is associated with adverse outcomes. Reduced kidney function may predispose to frailty. The relationship between serum β2-microglobulin (B2M), a novel marker of kidney function, and frailty has been studied very little. PURPOSE: This study aimed to investigate whether higher serum B2M levels were associated with prevalent and incident frailty in community-dwelling older women. METHODS: To examine prevalent frailty, we included 1,191 participants with adequate data for assessing frailty status (based on the Fried criteria) and B2M in a baseline survey of community-dwelling women aged ≥75 years. To examine incident frailty, we analyzed a subset of 456 participants without baseline frailty and with a repeated frailty assessment at a 4-year on-site clinical follow-up. Adjusted odds ratios (ORs) for the main confounders were obtained using logistic regression. RESULTS: There were 241 (20.2%) women with prevalent frailty at baseline and 67 (14.7%) with incident frailty at the 4-year follow-up. In a multivariable analysis adjusted for multiple potential confounders, B2M categories of 1.6-1.8 and 1.9-2.1 mg/L were associated with 2.24- and 2.05-fold greater odds of frailty, respectively, compared with prevalent frailty of B2M <1.6 mg/L. When modeled as continuous variables after adjusting for potential confounders and baseline status, higher B2M levels continued to be associated with incident frailty (odds ratio: 1.36, 95% CI: 1.03-1.80). After further adjustment for potential biochemical mediators, there was no evidence of an association between higher B2M levels at baseline and greater odds of frailty at follow-up. CONCLUSIONS: Higher B2M levels were independently associated with greater frailty at baseline in older adults but only slightly associated with increased risk of incident frailty at the 4-year follow-up. Higher B2M might be a consequence of frailty, rather than a cause.