Handgrip Weakness and Asymmetry Independently Predict the Development of New Activity Limitations: Results from Analyses of Longitudinal Data from the US Health and Retirement Study

Objectives Examining strength asymmetries in assessments of muscle function may improve screenings for limitations in independent living tasks such as instrumental activities of daily living (IADL). We sought to determine the associations between handgrip strength (HGS) asymmetry and future IADL limitations in aging Americans. Design Longitudinal panel. Setting and Participants Secondary analyses of data from participants aged at least 50 years from the 2006-2016 waves of the Health and Retirement Study. The analytic sample included 18,235 Americans who identified hand dominance and had measures of HGS for both hands in a single wave. Methods Hand dominance was self-reported, and a handgrip dynamometer measured HGS on each hand. The highest HGS values on each hand were used to calculate the HGS asymmetry ratio: (nondominant HGS/dominant HGS). Individuals with HGS asymmetry ratio <0.80 or >1.20 had HGS asymmetry. Persons with HGS asymmetry ratio <0.80 had dominant HGS asymmetry, whereas participants with HGS asymmetry ratio >1.20 had nondominant HGS asymmetry. Persons with HGS asymmetry ratio <1.0 also had their ratio inversed to make all HGS asymmetry ratios ≥1.0. IADL were self-reported. Covariate-adjusted generalized estimating equations were used for the analyses. Results Participants with HGS asymmetry had 1.12 [95% confidence interval (CI): 1.03-1.20] greater odds for future IADL limitations. Each HGS asymmetry dominance group also had greater odds for future IADL limitations: 1.09 (CI: 1.01-1.18) for individuals with dominant HGS asymmetry and 1.29 (CI: 1.09-1.52) for persons with nondominant HGS asymmetry. Every 0.10 increase in inverted HGS asymmetry ratio was associated with 1.30 (CI: 1.07-1.57) greater odds for future IADL limitations. Conclusions and Implications Assessing HGS asymmetry, as another potential biomarker of impaired muscle function, may provide novel insights for predicting IADL limitations. Future research should continue examining how strength asymmetries, and other aspects of muscle function beyond maximal strength, factor into the disabling cascade.