OBJECTIVES
Dynapenia refers to the age-related loss of muscle strength. Recent studies have reported that decreased muscle strength, such as handgrip strength (HGS), is associated with cognitive impairment in older adults. From the perspective of the weakness of the neuromuscular systems, decreased muscle strength may be closely related to cognitive decline. However, changes in muscle strength and cognitive function may occur simultaneously as a reflection of aging. The purpose of this study was to investigate the relationship between repeated measures of muscle strength and changes in cognitive function, as well as the new onset of mild cognitive impairment (MCI) in middle-aged and older adults, using Korean Longitudinal Study of Aging (KLoSA) data.
METHODS
This study included 10,516 adults (4,671 males and 5,845 females, mean age: 60.6 ± 10.7 years). Muscle strength was measured using HGS. HGS was divided into quartiles. Dynapenia was defined as HGS<28kg for men and <18kg for women. MCI was defined as the Korean Mini-Mental State Examination (K-MMSE) scores having less than 24. A logistic regression model was used to determine the associations between the changes in muscle strength and the risk of MCI after adjusting for covariates. In addition, a cox proportional hazard model was used to examine dynapenia and the risk of new onset of MCI.
RESULTS
Dynapenia and the lowest HGS quartile were significantly associated with an increased risk of MCI in cross-sectional analysis. In longitudinal analysis, the odds ratios (ORs) for MCI were 1.84 (95% CI, 1.71 to 1.97) in dynapenia, 2.07 (95% CI, 1.85 to 2.31) in the lowest absolute HGS and 2.17 (95% CI, 1.95 to 2.42) in the lowest relative HGS. After a 14-year follow-up, the hazard ratio (HR) for MCI was 1.29 (95% CI, 1.15 to 1.46) among participants with newly diagnosed dynapenia, and 1.29 (95% CI, 1.14 to 1.47) among participants who had persistent dynapenia after 2 years.
CONCLUSIONS
Our prospective cohort study showed that dynapenia and lower muscle strength are associated with an increased risk of MCI over time. Thus, our findings suggest that maintaining muscle strength may reduce the risk of cognitive function decline.