The longitudinal associations of sarcopenia definitions with functional deterioration: a comparative study.

Objective: Probable sarcopenia is a predictor of functional limitation in older adults. However, whether standard thresholds recommended by guides, or population-specific thresholds better predict impairment in functionality is an issue that needs to be enlightened. We aimed to study the associations of probable sarcopenia identified by the use of EWGSOP2 and population-specific thresholds with deterioration in functionality at follow-up and give prevalences of probable sarcopenia with different thresholds in older outpatients admitted to a tertiary health center.

Methods: In this retrospective, longitudinal follow-up study, we assessed handgrip strength (HGS) at the admission with a Jamar hand-dynamometer and diagnosed probable sarcopenia with standard and population-specific thresholds, i.e., 27 kg/16 kg, and 35 kg/20 kg in males/females, respectively. We evaluated activities of daily living (ADL) and instrumental ADL (IADL), with Katz and Lawton scales, at the admission and follow-up. To study whether probable sarcopenia was a predictor of impaired functionality, we defined two models for Cox regression analysis. We performed adjustments for age, sex, and nutritional status (assessed by Mini-Nutritional Assessment-Short Form) in Model 1 and defined Model 2 by adding low gait speed and frailty to the variables in Model 1.

Results: Among a total of 1970 patients, 195 had follow-up of median 560 days. The mean age was 75.5 ± 5.5, and 142 (72.8%) were female. In the basal evaluation, the prevalences of probable sarcopenia defined by the standard cut-offs and by population-specific cut-offs were 8.7% and 35.4%, respectively. In univariate analyses (Kaplan-Meier log-rank test), probable sarcopenia by population-specific cut-offs, but not EWGSOP2-cut-offs, was associated with deteriorations in both ADL (p = 0.04) and IADL (p < 0.001). In multivariate analyses, only the probable sarcopenia identified by population-specific cut-offs was independently associated with impairment in IADL in both models [HR (95%CI) = 1.88 (1.07-3.30), and 1.9 (1.04-3.6); for Model 1 and Model 2, respectively)].

Conclusion: Our findings suggested that the definition of probable sarcopenia identified by not standard, but population-specific thresholds more reliably predicted longitudinal deterioration of functionality in older outpatients. This finding might be considered as evidence supporting the use of population-specific cut-offs when the concern is sarcopenia diagnosis.