Incidence of Dementia and Alzheimer's Disease, Genetic Susceptibility, and Grip Strength Among Older Adults

Background Grip strength has prognostic value for aging-related health outcomes. Whether the associations of grip strength with the risk of dementia and Alzheimer's disease (AD) vary by the genetic risk of AD and related dementias (ADD) is unknown.Methods This study included 148 659 older adults of white British ancestry (aged >= 60 years) participating in UK Biobank with no dementia, and self-reported poor health status at baseline. Polygenic risk scores (PRS) for ADD were calculated based on 64 genetic variants. Grip strength was measured by hand dynamometers.Results The hazard ratios (HR) of dementia (n = 4 963) and AD (n = 2 373) for high genetic risk of ADD were 2.36 (95% confidence interval [CI]: 2.15-2.59) and 3.00 (95% CI: 2.61-3.44), respectively, compared with low genetic risk. Compared with the bottom tertile of grip strength, the top tertile of grip strength had a hazard ratio (HR) of 0.69 (95% CI: 0.64-0.74) for incident dementia, and 0.74 (95% CI: 0.66-0.82) for incident AD, after adjustment for confounders and PRS for ADD. The risk of dementia and AD was lower with the top grip strength tertile within each level of genetic susceptibility to ADD. There was no evidence of multiplicative interaction between grip strength and genetic susceptibility to ADD for both dementia (p value: .241) and AD (p value: .314).Conclusions Older adults with higher PRS for ADD are at higher risk of developing dementia and AD. The risk of dementia and AD was lower in individuals with higher grip strength, regardless of their level of genetic susceptibility to ADD.