Walking 5,000–7,500 steps a day may delay Alzheimer's cognitive decline by up to seven years

Walking between 5,000 and 7,500 steps a day could delay the cognitive decline associated with Alzheimer's disease by roughly seven years, according to a large study published in Nature Medicine — and a separate UCLA study finds that crossing the 4,000-step threshold is enough to produce measurable changes in the brain regions that govern memory and attention.

The Nature Medicine findings come from scientists at Mass General Brigham, who tracked 296 adults aged 50 to 90 — none showing cognitive impairment at the outset — over an average of 9.3 years as part of the Harvard Aging Brain Study. Participants wore waistband pedometers and underwent PET scans to measure amyloid-beta plaques and tau tangles, the two proteins most closely associated with Alzheimer's progression, and completed yearly cognitive assessments.

The results broke down by step count. People walking 3,000 to 5,000 steps a day experienced roughly three years of delay in cognitive decline. Those reaching 5,000 to 7,500 steps saw that delay extend to around seven years. Participants who were largely inactive showed faster accumulation of tau proteins and more rapid declines in thinking skills and daily functioning, according to Science Daily.

Crucially, the benefit was concentrated among participants who already had elevated amyloid-beta — the group most at risk. Among those with low amyloid-beta, there was little evidence of cognitive decline or tau buildup regardless of activity level, and no significant link to step counts. Statistical modeling indicated that the primary mechanism behind physical activity's benefit was its association with slower tau accumulation.

This sheds light on why some people who appear to be on an Alzheimer's disease trajectory don't decline as quickly as others. Lifestyle factors appear to impact the earliest stages of Alzheimer's disease, suggesting that lifestyle changes may slow the emergence of cognitive symptoms if we act early.— Jasmeer Chhatwal, MD, PhD, senior author and neurologist, Mass General Brigham

The UCLA study, published in a preprint edition of the Journal of Alzheimer's Disease, approached the question from a different angle: brain structure rather than protein buildup. Researchers recruited 29 adults aged 60 and older who reported memory complaints, tracked their steps for seven days using accelerometers, and divided them into two groups — those walking more than 4,000 steps daily and those walking fewer.

Those in the more active group had a thicker hippocampus — the small, memory-critical region deep within the brain — and thicker surrounding regions than their less active peers. They also outperformed on tests of attention, information-processing speed, and executive functioning, the set of mental skills involved in planning and goal-setting. Lower physical activity correlated with thinner brain structures and lower cognitive functioning, according to UCLA Health.

Few studies have looked at how physical activity affects the thickness of brain structures. Brain thickness, a more sensitive measure than volume, can track subtle changes in the brain earlier than volume and can independently predict cognition, so this is an important question.— Prabha Siddarth, first author and biostatistician, Semel Institute for Neuroscience and Human Behavior at UCLA

The two studies use different methods and populations — the Mass General Brigham work is longer, larger, and focused on people at elevated Alzheimer's risk, while the UCLA study is smaller and centered on structural brain changes — but they point toward the same practical conclusion: moderate daily walking produces detectable benefits in the brain regions and proteins most relevant to cognitive aging.

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. These findings show us that it's possible to build cognitive resilience and resistance to tau pathology in the setting of preclinical Alzheimer's disease.— Reisa Sperling, MD, co-author and co-principal investigator, Harvard Aging Brain Study

The Mass General Brigham team plans to investigate which types of physical activity are most beneficial, including how intensity and long-term exercise patterns influence brain health, and to uncover the biological mechanisms linking physical activity, tau buildup, and cognitive function. They also aim to inform future clinical trials testing exercise-based interventions in older adults at elevated Alzheimer's risk. The UCLA researchers said future studies will track participants over a longer period to better understand the causes of hippocampal thinning.

We want to empower people to protect their brain and cognitive health by keeping physically active. Every step counts — and even small increases in daily activities can build over time to create sustained changes in habit and health.— Wai-Ying Wendy Yau, MD, first author and cognitive neurologist, Mass General Brigham

Why it matters — For the tens of millions of older adults at risk of Alzheimer's, these studies offer a concrete, low-cost target — a few thousand daily steps — that may meaningfully slow the brain changes driving the disease, years before symptoms appear.

Reported by uclahealth.org, sciencedaily.com