Even light physical activity can slow the progression of Alzheimer's disease - study

This conclusion was reached by researchers from the Mass General Brigham Medical Network, whose work was published in the journal Nature Medicine.

The scientists analysed data from 296 people aged 50 to 90 years who participated in the Harvard Aging Brain Study project. All participants had no cognitive impairment at baseline, but some had elevated levels of amyloid-beta, a protein associated with the formation of plaques in the brain in Alzheimer's disease.

Using pedometers, the researchers monitored physical activity levels and PET scans tracked the accumulation of abnormal amyloid and tau proteins in the brain. The follow-up lasted an average of nine years, and for some participants, up to 14 years.

The results were impressive. People who walked 3,000 to 5,000 steps a day experienced, on average, a slowing of cognitive decline for about three years. Those who took 5,000 to 7,500 steps gained up to seven years compared to sedentary participants.

The sedentary people had a faster accumulation of tau proteins - a substance that damages nerve cells - and thus accelerated deterioration in memory and ability to perform daily activities.

"This explains why some people at risk for Alzheimer's disease age mentally slower than others," notes study leader Dr Jasmir Chhatwal of Mass General Brigham's neurology department. - "Lifestyle can influence the earliest stages of the disease, which means timely behavioural changes can delay the onset of symptoms."

The scientists emphasised that the benefit of physical activity was seen specifically in those who already had signs of amyloid plaques - that is, in the preclinical phase of Alzheimer's disease. In participants without such changes, the link between activity and cognitive health was minimal.

According to neuroscientist Reisa Sperling, a co-author of the study, these findings confirm: regular walks and other moderate exercise can strengthen the brain's cognitive "resistance" - its ability to resist damage caused by tau proteins.

"Every step counts," added the paper's first author Dr Wai-Ying Wendy Yau. - Even small increases in daily activity over time have tangible results for the brain and the whole body."

The researchers now plan to study which parameters of physical activity are most effective - duration, intensity or regularity. They also intend to find out what biological mechanisms link movement with slowing down degenerative processes in the brain.

According to the authors, the data obtained will help to develop dementia prevention programmes and clinical trials aimed at preserving cognitive health in old age.