Every Step Counts In Slowing Alzheimer’s: Researchers

Every step matters when it comes to protecting the brain, say researchers from Mass General Brigham, whose new study suggests that even modest physical activity may help slow the progression of Alzheimer’s disease, a neurodegenerative disorder affecting older adults at risk.

Walking as few as 3,000 to 5,000 steps a day can make a measurable difference, according to the findings published in Nature Medicine, which point to a tangible link between daily movement and cognitive health.

The study found that individuals who walked within this range experienced significantly slower rates of cognitive decline and a reduced buildup of harmful brain proteins compared with those leading more sedentary lives.

On average, cognitive decline was delayed by about three years in those taking 3,000–5,000 steps daily, and by seven years in those walking between 5,000 and 7,500 steps.

By contrast, participants with low activity levels showed faster accumulation of tau proteins in the brain and a more rapid decline in cognition and daily functioning.

“This sheds light on why some people who appear to be on an Alzheimer’s disease trajectory don’t decline as quickly as others,” said Dr. Jasmeer Chhatwal, senior author of the study and neurologist at the Mass General Brigham Department of Neurology.

“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.”

The researchers analysed data from 296 participants aged 50 to 90 years enrolled in the Harvard Aging Brain Study, all of whom were cognitively unimpaired at the outset. Using PET brain scans, the team measured baseline levels of amyloid-beta and tau — proteins linked to Alzheimer’s pathology — and assessed participants’ physical activity through pedometers worn at the waist.

The cohort underwent annual cognitive assessments for up to 14 years, with a subset receiving follow-up brain scans to track protein buildup.

The results revealed that higher step counts were associated with slower rates of both cognitive decline and tau accumulation, particularly among individuals with elevated baseline levels of amyloid-beta. Statistical modelling suggested that much of the benefit from physical activity was mediated by a reduction in tau buildup.

In contrast, participants with low amyloid-beta levels showed little evidence of cognitive decline or tau accumulation over time, regardless of their activity levels — underscoring that the benefit of exercise may be greatest for those already at heightened risk.

“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 Dr. Reisa Sperling, co-principal investigator of the study.

“These findings show that it is possible to build cognitive resilience and resistance to tau pathology in the preclinical stages of Alzheimer’s disease. This is particularly encouraging for our goal of preventing Alzheimer’s dementia and other forms of late-life cognitive impairment.”

The researchers plan to further explore which aspects of physical activity — such as intensity, duration, or consistency — contribute most to brain protection. They also intend to study the biological mechanisms linking exercise, tau pathology, and cognition, which could inform the design of future clinical trials testing lifestyle-based interventions for dementia prevention.

“We want to empower people to protect their brain and cognitive health by staying physically active,” said Dr. Wai-Ying Wendy Yau, the study’s first author. “Every step counts — and even small increases in daily movement can, over time, lead to lasting improvements in health.”

The study holds particular significance for India, where Alzheimer’s disease is fast emerging as a major public health concern, driven by rapid population ageing, lifestyle changes, and increasing health risks. Recent national estimates suggest that about 8.8 million Indians aged 60 years and above currently live with dementia — a large proportion of whom are affected by Alzheimer’s disease. If current prevalence rates persist, the number is projected to nearly double to 16.9 million by 2036 and triple by 2050, largely due to demographic ageing. The growing burden of Alzheimer’s and related dementias, experts warn, will place mounting pressure on families, caregivers, healthcare systems, and social welfare networks across the country.