Leisure-time exercise linked to lower dementia risk

For years, scientists have known that regular physical activity can help lower the risk of dementia. But new USC research suggests that it's not only the amount but also the activity's context - for work or for leisure - that makes a difference.

A meta-analysis of more than 4.2 million people has found that leisure-time exercise - activities such as walking, cycling, running, swimming or playing sports - is associated with a substantially lower risk of dementia. In contrast, physical activity performed as part of a job appears to be linked with a higher risk of developing the condition.

The findings, published in The Lancet Public Health, are the first to systematically examine whether the so-called "physical activity paradox" extends to dementia. This paradox, well documented in cardiovascular research, describes the surprising observation that physically demanding jobs do not provide the same health benefits as voluntary exercise - and may even increase disease risk.

The research team, led by Professor of Biological Sciences and Anthropology David Raichlen of the USC Dornsife College of Letters, Arts and Sciences, analyzed data from 74 cohort and case-control studies involving more than 4.2 million participants aged 45 to 93 years across 30 countries. Participants were followed for a median of 10 years, during which investigators tracked diagnoses of all-cause dementia, Alzheimer's disease and vascular dementia.