Author(s): ZHAI, X., CHOI, H.R., ZHONG, J., DAI, Y., SAWADA, S.S. , Institution: THE UNIVERSITY OF HONG KONG, Country: HONG KONG, Abstract-ID: 174

INTRODUCTION:
The association between muscle strength, as measured by handgrip strength (HGS), and dementia has been well-established. However, the role of HGS asymmetry in dementia risk remains understudied. This study investigated the independent and joint associations of HGS asymmetry and weakness with incident dementia in the Survey of Health, Ageing and Retirement in Europe (SHARE) study with a follow-up of 18 years.
METHODS:
This cohort study analyzed participants aged ≥ 50 years from SHARE (2004-2022) across 28 countries. Dementia was ascertained using the following question: “Doctor has said you had: Alzheimer’s disease, dementia, or senility”. HGS was measured in kg using a dynamometer. HGS asymmetry was defined as a >10% difference between hands (HGS ratio < 0.9 or > 1.1). Weakness was defined as maximum HGS < 27 kg in men or <16 kg in women per EWGSOP criteria. We created four combinations of HGS asymmetry and weakness to permit a joint analysis: ‘both asymmetry and weakness’, ‘weakness only’, ‘asymmetry only’, and ‘neither asymmetry nor weakness’. Time-varying Cox regression models were employed to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs), adjusting for potential confounders including age, sex, education (less than upper secondary, upper secondary and vocational, and tertiary education), marital status (married, partnered, separated, divorced, widowed, and never married), residence (rural/urban), geographical region (Eastern, Northern, Southern, Western Europe, and Israel), body mass index (underweight, normal weight, overweight, and obesity classes I-III), smoking status (never, previous, and current), weekly alcohol consumption (yes/no), physical activity (very low, moderately low, moderately high, and high), number of medications, and maximum HGS or HGS asymmetry.
RESULTS:
The study included 99,077 participants (54.9% women, mean age 66.6 years). Prevalence of HGS asymmetry and weakness were 49.4% and 6.8%. Over a mean follow-up of 7.6 years, there were 4,513 cases of dementia. The incidence of dementia was 6.0 per 1000 person-years (95% CI: 5.85, 6.20). Participants without HGS asymmetry had lower dementia risk [HR: 0.88 (95% CI: 0.79, 0.97)], after adjusting for all confounders including maximum HGS. The HR (95% CI) for dementia in the normal group was 0.50 (0.44, 0.56) compared to the weakness group, after adjusting for all confounders includings HGS asymmetry. In the joint analyses, compared with the ‘both asymmetry and weakness’ group, the HRs (95% CIs) for dementia were 0.81 (0.68, 0.98), 0.49 (0.42, 0.56), and 0.44 (0.38, 0.51) in the ‘weakness only’, ‘asymmetry only’, and ‘neither asymmetry nor weakness’ groups.
CONCLUSION:
HGS asymmetry and weakness were independently associated with dementia risk, with their co-occurrence conferring the highest risk. These findings suggest that clinical assessments targeting both muscle symmetry and muscle strength may contribute to the detection of dementia and inform effective intervention strategies.