A study reveals that physical exercise can delay the onset of Alzheimer's symptoms by up to seven years.

Physical activity can delay the onset of Alzheimer 's disease symptoms by up to seven years in people at risk, according to research published Monday in the journal Nature Medicine . A team of scientists from Australia, Canada, and the United States followed nearly 300 people with preclinical Alzheimer's for 14 years. These individuals had no symptoms of the disease but exhibited a high accumulation of Tau and Beta-amyloid proteins in their brains, placing them at high risk.

Scientists aimed to determine whether physical activity, even moderate activity, influenced the development of the disease. Their results have confirmed that it does. Older adults who walk fewer than 3,000 steps a day and have elevated levels of the beta-amyloid protein in their brains, clearly associated with the development of Alzheimer's, show faster cognitive decline compared to more active individuals.

Conversely, cognitive decline and loss of functionality in daily life activities are delayed by an average of three years in people who walk between 3,000 and 5,000 steps a day, and by an average of seven years in those who walk at least between 5,000 and 7,500 steps a day.

"Our finding shows that increasing the number of steps, even slightly, can help slow the progression of Alzheimer's disease in people at high risk of developing it," says one of the authors, Jasmeer Chhatwal, a neurologist at Mass General Brigham, a medical research consortium between Harvard University and Boston's most prestigious hospitals.

According to Chhatwal, his discovery would explain why some people at risk of Alzheimer's deteriorate more rapidly than others cognitively, while also allowing lifestyle changes to be used as a therapeutic strategy.

Researchers analyzed data from 296 participants aged 50 to 90 from the Harvard Brain Aging Study, all of whom had no cognitive impairment at the start of the study. They used a non-invasive test that measures the body's metabolic activity in real time (Positron Emission Tomography, PET) to measure baseline levels of beta-amyloid in plaques and tau in neurofibrillary tangles in the participants' brains.

Simultaneously, participants' physical activity was measured using waist-worn pedometers. Participants underwent annual follow-up cognitive assessments for a period of between 2 and 14 years (an average of 9.3 years), and a subgroup also underwent PET scans to analyze changes in Tau protein.

The results showed that a higher number of steps was associated with slower rates of cognitive decline and slower accumulation of Tau protein in participants with elevated baseline levels of beta-amyloid protein. Exercise, therefore, slows the accumulation of Tau protein, and a lack of it has the opposite effect.

"Our study shows that every step counts, and even a small increase in activity leads to improved brain and cognitive health. Staying physically active is one way to protect your brain ," said another of the authors, Wai-Ying Wendy Yau, a neurologist at Mass General Brigham, in a statement from the center.

Looking ahead, researchers plan to delve deeper into which aspects of physical activity may be most important in slowing Alzheimer's, and into the biological mechanisms that underlie this influence.

The authors believe it is crucial that this work can help design future clinical trials testing exercise interventions to slow cognitive decline in old age, especially in people at high risk of developing Alzheimer's disease.