Physical activity in mid-life could lower dementia risk by 45%: US study

Regular physical activity during mid-life years and later could lower one's risk of developing dementia by up to 45 per cent, compared to those who are less active during the period, found an analysis of over 4,300 adults in a US town.

The findings, published in The Journal of the American Medical Association (JAMA), could help develop strategies that are timed to the most relevant stages of adult life, researchers said.

Dementia is an ageing-related condition in which one's memory, thought processes and speech are steadily impacted over time, and can eventually interfere with daily activities. Alzheimer's disease is the most common form of dementia.

Researchers from Boston University School of Medicine looked at data from the 'Framingham Heart Study', which began in 1948 and recruited men and women from the town of Framingham in the US state of Massachusetts. The participants were followed up for a period of up to 37 years.

"Individuals with the highest levels of physical activity at mid-life and late-life had 41 per cent and 45 per cent lower risk of all-cause dementia, respectively, compared with those with the lowest levels of physical activity," authors wrote.

Among the participants — 1,526 young adults, 1,943 in mid-life and 855 in late years — 567 cases of dementia were noted at the end of the follow-up period.

Moderate levels of physical activity was associated with 35-38 per cent lower risk of dementia, compared to the least physically active ones.

The researchers also looked at how carrying the 'APOE e4' gene variant — considered among the strongest factors for developing Alzheimer's disease — impacted the link between physical activity and dementia risk.

For those not carrying the gene variant, highest levels of physical activity during mid-life were linked to a nearly 50-60 per cent lower risk of dementia, while highest levels during late-life resulted in a 46 per cent lower risk, compared to lowest levels of activity.

However, for those carrying the gene variant, highest levels of physical activity in late-life was related with a 66 per cent lower dementia risk, compared to lowest levels.

The authors said physical activity can directly slow down the production of amyloid clumps — accumulation of amyloid proteins causing cell death — in the brain, a phenomenon considered intrinsic to Alzheimer's disease.

Physical activity can also improve brain structure and function by promoting growth of neurons in hippocampus, responsible for memory, they said.