Handgrip strength asymmetry is associated with the risk of neurodegenerative disorders among Chinese older adults
Zi Chen, Mandy Ho, Pui Hing Chau
Abstract
BACKGROUND: Neurodegenerative disorders, as the irreversible condition, have a long, silent preclinical period. Recognition of early physical signs of neurodegenerative disorders had important practical implications for identifying at-risk population. The aim of this study was to investigate whether handgrip strength (HGS) asymmetry was associated with the incidence of neurodegenerative disorders among Chinese older adults. METHODS: This study used the data of participants aged 60 years and over from three waves (2011-2015) of China Health and Retirement Longitudinal Study. HGS asymmetry was measured with HGS ratio (maximal non-dominant HGS/maximal dominant HGS), with the value less than 0.9 or more than 1.1 considered as HGS asymmetry. Physician-diagnosed neurodegenerative disorders were identified by self-reported or proxy-reported information. Competing risk analysis was conducted to examine the association between HGS asymmetry and incident neurodegenerative disorders, with mortality treated as the competing event. RESULTS: A total of 4925 participants were included in the analysis [mean (SD) age: 68.1(6.68); female: 49.7%]. Eight hundred and eighty-eight (18.0%) participants had low HGS and 2227 (45.2%) had HGS asymmetry. During the 4 years of follow-up, there were 156 cases of neurodegenerative disorders and 422 cases of mortality. The incidence of neurodegenerative disorders was 8.7 per 1000 person-years [95% confidence interval (CI): 7.4-10.2], and the incidence of mortality was 23.5 per 1000 person-years (95% CI: 21.4-25.9). Both the cause-specific model and the Fine-Gray subdistribution hazard model showed that participants with HGS asymmetry had increased hazard of neurodegenerative disorders [hazard ratio (HR) = 1.66, P = 0.002, 95% CI: 1.202-2.297; subdistribution hazard ratio (SHR) = 1.65, P = 0.002, 95% CI: 1.202-2.285]. Low HGS, but not HGS asymmetry, was related to the higher hazard of mortality (HR = 1.61, P < 0.001, 95% CI: 1.297-1.995; SHR = 1.58, P < 0.001, 95% CI: 1.286-1.951). CONCLUSIONS: Handgrip strength asymmetry was associated with the future risk of neurodegenerative disorders among Chinese older adults. Public healthcare providers could consider examining HGS asymmetry along with the maximal HGS as a way to identify those at elevated risk of neurodegenerative disorders.