Growing evidence demonstrates that lifestyle behaviors modify dementia risk. Investigators from the Harvard Aging Brain Study assessed the effects of physical activity on β-amyloid ( peptide  crucially involved in Alzheimer’s disease as the main component of the amyloid plaques found in the brains of people with Alzheimer’s disease) burden, longitudinal cognitive decline, and neurodegeneration ( the progressive loss of structure or function of neurons, including death of neurons) in cognitively normal older adults.

Baseline physical activity was the daily number of steps counted over 5 to 7 days by a waistband pedometer (~5500 daily steps in these participants); β-amyloid burden was determined via Pittsburgh Compound B positron emission tomography (Positron emission tomography (PET) is a type of nuclear medicine procedure that measures metabolic activity of the cells of body tissues) , and vascular risk was calculated with the Framingham Heart Study cardiovascular disease risk score (estimates risk of heart attack in 10 years) .  Longitudinal neurodegeneration was measured by loss of gray matter ( part of the brain that contains most of the brain’s neuronal cell bodies) and cortical thickness (Cortex is the outer layer of the brain) seen on brain MRI, and a cognitive composite score indicated cognitive change over time.

Cross-sectional analysis of the 182 participants (57% female; mean age, 73), showed that greater physical activity was associated with lower vascular risk but not with β-amyloid burden. After a follow-up of 5 to 6 years, higher physical activity was associated with slower β-amyloid–related cognitive decline and gray-matter volume loss in multivariable analyses. Lower vascular risk was independently associated with slower β-amyloid–related cognitive decline and volume loss. Exploratory whole-brain analyses associated greater physical activity with slower β-amyloid–related cortical thinning in the entorhinal, insular, lateral temporal, and medial parietal regions but not the hippocampus.

Citation: Rabin JS et al. Associations of physical activity and β-amyloid with longitudinal cognition and neurodegeneration in clinically normal older adults. JAMA Neurol 2019 Jul 16; [e-pub]. (https://doi.org/10.1001/jamaneurol.2019.1879)

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Comments: many studies indicated that physical activity could help with dementia; this is a longitudinal study with biomarkers demonstrating the benefits- impressive-BA