Weakness May Cause Mortality In Older Americans: A Matched Cohort Analysis

Abstract

Muscle weakness has been implicated with early mortality; however, quantifying the extent of this association with a carefully matched not weak and strong control will help to better establish the impact of weakness on premature death. PURPOSE: We utilized a propensity cohort analysis in a national sample of older Americans for this study to determine if persons who were weak had a higher risk for early mortality compared to a not weak or strong control group. METHODS: Data from 19,729 Americans aged at least 50 years from 2006-2014 waves of the Health and Retirement Study were analyzed. Handgrip strength was measured with a hand-grip dynamometer. Men with handgrip strength <26 kilograms were considered weak, ≥26 kilograms were considered not weak, and ≥32 kilograms were considered strong. Women with handgrip strength <16 kilograms were classified as weak, ≥16 kilograms were classified as not weak, and ≥20 kilograms were classified as strong. The National Death Index and postmortem interviews determined date of death. The greedy matching algorithm was used to separately match the weak cohort 1:1 to a 1) not weak control cohort, and 2) strong control cohort on several influential covariates. Kaplan-Meier estimators examined survival probabilities and Cox models determined the association between weakness and time to mortality for each of the matched pairs. RESULTS: Of the 1,077 weak and not weak matched pairs, 401 weak (37.2%; mortality rate per 1,000 person years: 90.6) and 296 not weak (27.4%; mortality rate per 1,000 person years: 57.8) older Americans died over an average 4.4±2.5 year follow up. There were 392 weak (37.0%; mortality rate per 1,000 person years: 89.6) and 243 strong (22.9%; mortality rate per 1,000 person years: 46.7) persons that died over a mean 4.5±2.5 year follow up from the 1,057 weak and strong matched pairs. Those in the weak cohort had a 1.40 (95% confidence interval (CI): 1.19-1.64) and 1.54 (CI: 1.30-1.83) higher hazard for mortality relative to older Americans in the not weak and strong control cohorts, respectively. CONCLUSION: Our findings may indicate a causal association between muscle weakness and mortality in older Americans. Healthcare providers should include measures of handgrip strength as part of routine health assessments and discuss the health risks of weakness with their patients.