Even a moderate amount of physical activity may delay the onset of Alzheimer’s disease in at-risk older adults

A small increase in step count may help slow the progression of Alzheimer’s disease among people at high risk, a new study suggests. In a paper published in natural medicineMass General Brigham researchers found that physical activity was associated with a slower rate of cognitive decline in older adults with high levels of amyloid beta, a protein linked to Alzheimer’s disease.

For people who walked only 3,000 to 5,000 steps a day, cognitive decline was delayed by an average of 3 years, and for those who walked 5,000 to 7,500 steps a day, it was delayed by 7 years. People who lead sedentary lifestyles had a much faster buildup of tau protein in their brains and a faster decline in cognitive and daily functioning.

“This sheds light on why some people who appear to be on track for Alzheimer’s disease do not decline as quickly as others,” said lead author Jasmeer Chhatwal, MD, of the Mass General Brigham Department of Neurology. “Lifestyle factors appear to influence the early stages of Alzheimer’s disease, suggesting that lifestyle changes, if taken early, may delay the appearance of cognitive symptoms.”

Researchers analyzed data from 296 participants aged 50 to 90 who participated in the Harvard Aging Brain Study. Neither of these participants had cognitive impairment at the start of the study. They used PET brain scans to measure baseline levels of amyloid beta in plaques and tau in tangles and assessed participants’ physical activity using waistband pedometers.

Participants underwent annual follow-up cognitive assessments for 2 to 14 years (mean = 9.3 years), and a subset underwent repeat PET scans to track changes in tau.

More steps were associated with slower rates of cognitive decline and slower tau protein accumulation in participants with higher baseline levels of amyloid beta. The researchers’ statistical modeling suggested that most of the physical activity benefits associated with slowing cognitive decline were driven by slow tau accumulation.

In contrast, people with low baseline levels of amyloid beta showed little cognitive decline or tau protein buildup over time and no significant associations with physical activity.

“We are thrilled that data from the Harvard Aging Brain Study has helped the field better understand the importance of physical activity for maintaining brain health,” said co-author Reisa Sperling, MD, a neurologist at the Brigham Department of Neurology in Massachusetts and co-principal investigator of the Harvard Aging Brain Study.

“These findings demonstrate that it is possible to build cognitive resilience and resistance to tau pathology in the preclinical Alzheimer’s disease setting. This is particularly encouraging in our quest to ultimately prevent Alzheimer’s disease dementia and reduce multifactorial dementia.”

In the future, the researchers plan to look more deeply into which aspects of physical activity, such as exercise intensity and longitudinal activity patterns, are most important. They also plan to investigate the biological mechanisms linking physical activity, tau accumulation, and cognitive health.

Critically, the authors believe that this study may help design future clinical trials testing exercise interventions to slow late-life cognitive decline, particularly in individuals at high risk due to preclinical Alzheimer’s disease.

“We want to empower people to protect their brain and cognitive health by staying physically active,” said first author Wai-Ying Wendy Yau, MD, a cognitive neurologist at the Brigham Department of Neurology in Massachusetts.

“Every step counts. Even small increases in daily activity can lead to lasting changes in your habits and health over time.”