Key points Is reduced muscle strength, as measured by handgrip strength, associated with increased risk of dementia, poorer neuroimaging outcomes, and reduced cognition in both men and women? Findings This cohort study of 190,406 adults in the United Kingdom found associations for both men and women across multiple outcomes and with multiple adjustment strategies. Grip strength was associated with fluid intelligence, prospective memory, and dementia diagnoses; this association was more pronounced for vascular dementia. Meaning These findings add to a growing body of research suggesting that interventions designed to increase muscle strength, particularly among middle-aged adults, may hold promise for maintaining neurocognitive brain health. |
Introduction
Muscle strength is associated with numerous health outcomes, including measures of cognitive aging. This association suggests that there may be potential benefits of strength training in delaying age-related cognitive loss or dementia, but there is a paucity of evidence to inform such interventions. For example, the most relevant outcomes (cognitive function, clinical dementia, or neuroimaging), potential mechanisms, variability of outcomes between gender or age groups, and possible spurious explanations for the association have not been evaluated.
Handgrip strength (HGS) is a reliable measure of muscle strength feasible to assess in large samples. HGS offers the opportunity for a more detailed examination of how muscle strength is associated with multiple neurocognitive outcomes.
Numerous studies show that HGS is associated with worse scores on cognitive tests, but these associations are vulnerable to reverse causality bias if incipient dementia influences HGS. A recent systematic review identified 10 studies of HGS and incident dementia, but only 2 used clinically recorded dementia outcomes, and none included sufficient sample size or diversity to assess gender or age differences in associations.
There is almost no evidence available on whether the association between HGS and neurocognitive outcomes differs between middle and old age. Middle age is a particularly important window; Midlife precedes the onset of almost all dementias, and interventions in midlife have the greatest benefit for muscle strength.
In this study, we leverage data from the UK Biobank, a large, well-characterized sample of middle-aged and older men and women who did not have dementia at baseline to examine the associations of HGS with incident dementia, neuroimaging correlates, and cognition. We augmented the findings on the association of HGS with cognition by performing a Mendelian randomization analysis of the association between genetic risk of dementia and HGS.
We hypothesized that reduced muscle strength, as measured by HGS, would be associated with increased risk of dementia, worse neuroimaging outcomes, and reduced cognition in both men and women. We also hypothesized that genetic risk for dementia would not be associated with HGS.
Importance
Associations between muscle strength and cognitive outcomes have sparked interest in interventions that increase muscle strength for dementia prevention, but associations between muscle strength and cognitive aging are unclear, particularly among older adults. middle age.
Aim
To assess the association between handgrip strength (HGS) and dementia, reduced cognition and poorer neuroimaging outcomes in a UK population of middle-aged adults.
Design, environment and participants
This cohort study assessed UK Biobank participants aged 39 to 73 years enrolled between 2006 and 2010 with HGS measured and followed prospectively for dementia diagnosis. Data was analyzed from October 2021 to April 2022.
Exhibitions
HGS evaluated in both hands using a dynamometer.
Main results and measures
Outcomes included cognitive test scores (fluid intelligence and prospective memory), brain magnetic resonance imaging measures (total brain volume, white matter hyperintensity, and hippocampal volume), and incident dementia (all-cause and Alzheimer’s disease [ AD] from primary care, hospital or death records) during a median (IQR) of 11.7 (11.0-12.4) years of follow-up.
Mixed-effects linear and logistic regressions and Cox proportional hazards models were used to estimate associations, stratified by gender and adjusted for covariates. Estimates are presented per 5 kg decrement in HGS.
To assess reverse causality , we assessed whether a polygenic risk score for AD is associated with HGS.
Results
A subsample of 190,406 adult participants in the UK Biobank were evaluated (mean [SD] age, 56.5 [8.1] years; 102,735 women [54%]).
- A 5 kg decrease in HGS was associated with lower fluid intelligence scores in men (β, -0.007; 95% CI, -0.010 to -0.003) and women (β, -0.04; 95% CI). , -0.05 to -0.04).
- A 5-kg decrease in HGS was associated with worse odds of responding correctly to a prospective memory task for men (odds ratio, 0.91; 95% CI, 0.90 to 0.92) and women (odds ratio, 0.91; 95% CI, 0.90 to 0.92). , 0.88; 95% CI, 0.87 to 0.90).
- A 5-kg decrease in HGS was associated with greater white matter hyperintensity volume in men (β, 92.22; 95% CI, 31.09 to 153.35) and women (β, 83.56; 95% CI, 13.54 to 153.58).
- A 5-kg decrease in HGS was associated with incident dementia for men (hazard ratio, 1.20; 95% CI, 1.12 to 1.28) and women (hazard ratio, 1.12; 95% CI, 1.00 to 1.26).
Gender-stratified hazard ratios for diagnoses of dementia, Alzheimer’s disease and vascular dementia associated with a 5 kg decrease in handgrip strength (HGS) among 190,406 UK Biobank participants
Conclusions and relevance
These findings suggest that HGS is associated with measures of neurocognitive brain health among men and women and add to a growing body of research indicating that interventions designed to increase muscle strength , particularly among middle-aged adults, may hold promise for maintaining neurocognitive brain health.
Discussion
In this cohort of 190,406 individuals from a large, well-characterized prospective study of adults in the United Kingdom, we examined associations between HGS and multiple measures of neurocognitive brain health. We found associations for both men and women across multiple outcomes and with multiple adjustment strategies.
Lower HGS was associated with decreased fluid intelligence, lower odds of a correct score on a prospective memory test, and increased dementia diagnoses. This association was more pronounced for vascular dementia. Lower HGS was associated with greater white matter (WMH) volume for both men and women, but was not significantly associated with total brain volume or hippocampal volume.
Taken together, these results suggest that even small changes in muscle strength could have a non-trivial association with vascular dementia risk.
Our results are consistent with studies that have found that HGS and other measures of total body muscle strength are associated with cognitive status and incident dementia.
Conclusions Our cohort study provides evidence that HGS is associated with several markers of cognitive aging, including neuroimaging markers of cerebral small vessel disease and dementia subtypes. Our findings add to a small but growing body of research indicating that the association between muscle strength and dementia may be due to vascular mechanisms and that interventions designed to increase muscle strength, particularly among middle-aged adults, may hold promise. for the maintenance of neurocognitive capacity and brain health. |
