A new study shows a strong correlation between muscle strength and mobility and brain volume, including in the hippocampus that underlies memory function, in adults with Alzheimer’s disease (AD).
Investigators found statistically significant relationships between better handgrip strength and mobility and hippocampal and lobar brain volumes in 38 cognitively impaired adults with biomarker evidence of AD.
“The implication is that muscular strength and mobility influence brain health and can potentially be modified to improve outcomes in persons with Alzheimer’s,” study investigator Cyrus Raji, MD, PhD, Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri, told Medscape Medical News.
The study was published online December 14 in the Journal of Alzheimer’s Disease.
Brain-Body Connection
The researchers measured handgrip strength in patients’ dominant and nondominant hands using a hand dynamometer and calculated handgrip asymmetry. Mobility was measured via the 2-minute walk test. Together, the test results were used to categorize patients as “frail” or “not frail.”
They measured regional brain volumes using Neuroreader (Brainreader), a US Food and Drug Administration (FDA)-approved software application that measures brain volumes on MRI scans.
The investigators found higher nondominant handgrip strength was significantly associated with larger volumes in the hippocampal volume (P = .02). In addition, higher dominant handgrip strength correlated with higher frontal lobe volume (P = .02).
Results also showed higher scores on the 2-minute walk test were associated with larger hippocampal (P = .04), frontal (P = .01), temporal (P = .03), parietal (P = .009), and occipital lobe (P = .005) volumes. Frailty was associated with reduced frontal, temporal, and parietal lobe volumes.
“In this study we combined objective evaluations of frailty with measurable determinants of brain structure on MRI to demonstrate a link between frailty and brain health in patients with both biomarker evidence of AD and cognitive impairment,” study investigator Somayeh Meysami, MD, with Pacific Brain Health Center, Pacific Neuroscience Institute Foundation (PNI), Santa Monica, California, told Medscape Medical News.
The researchers noted it’s possible that interventions specifically focused on improving ambulatory mobility and handgrip strength could be beneficial in improving dementia trajectories.
‘Use It or Lose It’
The chief limitation of the study is the cross-sectional design that precludes drawing firm conclusions about the causal relationships between handgrip strength and changes in brain structure.
In addition, the study used a relatively small convenience sample of outpatients from a specialty memory clinic.
The researchers say future longitudinal analyses with a larger sample size will be important to better understand the possible directions of causality between handgrip strength and progression of atrophy in AD.
However, despite these limitations, the findings emphasize the importance of “body-brain connections,” added David A. Merrill, MD, PhD, director of the Pacific Brain Health Center at PNI.
“Training our muscles helps sustain our brains, and vice versa. It’s ‘use it or lose it’ for both body and mind. Exercise remains among the best strategies for maintaining a healthy body and mind with aging,” Merrill told Medscape Medical News.
“While it’s long been appreciated that aerobic training helps the brain, these findings add to the importance of strength training in supporting successful aging,” he added.
This work was supported by Providence St. Joseph Health, Seattle, Washington; Saint John’s Health Center Foundation; Pacific Neuroscience Institute Foundation; and the National Institutes of Health. Raji receives consulting fees from Brainreader, Apollo Health, Pacific Neuroscience Foundation, and patents/royalties from Neurevolution LLC. Merrill and Meysami reported no relevant disclosures.
J Alzheimer’s Dis. Published online December 14, 2022. Full text.
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