Objectives
Dynapenia is the age-related loss of muscle strength. Decreased muscle strength, includinghandgrip strength (HGS), is associated with cognitive impairment in older adults, possibly due to weakeningof the neuromuscular system. However, changes in muscle strength and cognitive function may occurs simultaneously and reflect aging. Previous studies that used cross-sectional study designs or single measurements of muscle strength may not adequately reflect the effects of changes in muscle strength overtime. We aimed to investigate the relationship between repeated measures of muscle strength and changesin cognitive function and new-onset mild cognitive impairment (MCI) in middle-aged and older adults.
Methods
This prospective cohort study used data from Korean Longitudinal Study of Aging (2006-2020) for10,516 adults (4,671 males and 5,845 females, mean age: 60.6 ± 10.7 years). Muscle strength was measuredusing HGS and divided into quartiles by sex. Dynapenia was defined as HGS <28 kg for men and <18 kg forwomen. MCI was defined as Korean Mini-Mental State Examination scores <24. Logistic regression analysiswas used to determine the associations between the changes in muscle strength and the risk of MCI afteradjusting for covariates. Additionally, a Cox proportional hazard model was used to examine the change indynapenia and the risk of new-onset of MCI after adjusting for covariates.
Results
In a cross-sectional analysis, dynapenia (odds ratio [OR] = 1.98; 95% confidence intervals [CI]: 1.75–2.24) and the lowest absolute (OR = 2.13; 95% CI: 1.73–2.62) and relative (OR = 2.29; 95% CI: 1.88–2.78) HGS were significantly associated with an increased risk of MCI. In longitudinal analysis, the ORs for MCI were 1.84 (95% CI: 1.71–1.97) in dynapenia, 2.07 (95% CI: 1.85– 2.31) in the lowest absolute HGS and 2.17 (95% CI: 1.95–2.42) in the lowest relative HGS. During a 14-year follow-up, the hazard ratio (HR) for MCI was 1.29 (95% CI:1.15–1.46) among participants with newly diagnosed dynapenia, and 1.29 (95% CI: 1.14–1.47) among participants who had persistent dynapenia after 2 years.
Conclusion
Our prospective cohort study showed that dynapenia and lower muscle strength were associated with an increased risk of MCI over time. Also, persistent and newly diagnosed dynapenia were associated with an increased risk of new-onset MCI. Thus, our findings suggest that early detection and prevention of dynapenia may prevent cognitive function decline.