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One Common Type of Physical Activity Linked to Higher Dementia Risk
0 Share Newsweek is a Trust Project member See more of our trusted coverage when you search. Prefer Newsweek on Google to see more of our trusted coverage when you search. For years, scientists have known that regular physical activity can help lower the risk of dementia . But a new study suggests that where and how people get that activity may matter just as much as how much they do.
A meta-analysis involving more than 4.2 million people found that leisure-time exercise, including activities such as walking, cycling, running, swimming and sports, was associated with a significantly lower risk of dementia. In contrast, physical activity performed as part of a person's job was linked to a higher risk of developing the condition.
Natan Feter, the study’s first author, told Newsweek : "Occupational physical activity often involves spending time in environments that may be less favorable to health, including greater exposure to air pollution and psychosocial stressors."
The findings, published in The Lancet Public Health , are the first to systematically investigate whether the "physical activity paradox" applies to dementia.
The paradox, already documented in cardiovascular research , refers to the observation that physically demanding jobs do not appear to provide the same health benefits as voluntary exercise and may even be associated with poorer health outcomes.
Feter said: "The observed associations may therefore partly reflect the cumulative effects of social, economi c, and environmental adversities rather than being fully attributable to occupational physical activity per se.
"This dimension of risk should be interpreted through a structural lens, recognizing these exposures as sociocultural and environmental drivers of health rather than as biological traits."
The Alzheimer's Association says an estimated 7.4 million Americans are living with Alzheimer's dementia.
The research team, led by David Raichlen, professor of biological sciences and anthropology at 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 between 45 and 93 across 30 countries.
Participants were followed for a median of 10 years, during which researchers tracked diagnoses of all-cause dementia, Alzheimer's disease and vascular dementia.
Overall, people who engaged in higher levels of leisure-time physical activity had a 24 percent lower risk of dementia compared with those who were least active. Household physical activity also appeared beneficial, although that finding was based on a single study.
"The findings challenge the long-held assumption that 'every move counts' for brain health ," said Feter, a postdoctoral fellow in Raichlen's Evolutionary Biology of Physical Activity Lab, in a statement.
The researchers noted that physical activity is often treated as a single category, despite including a wide range of activities such as exercise, manual labor, commuting and housework.
According to the authors, these different forms of movement take place in very different circumstances and may affect long-term health in distinct ways.
Feter told Newsweek : "Occupational physical activity often involves repetitive, low-complexity tasks that may limit the accumulation of cognitive reserve. It may also occur in environments characterized by hazardous exposures, such as air and noise pollution."
Whereas leisure-time activity is more likely to be self-selected, varied, and socially engaging.
"However, a single factor is unlikely to explain this association," Feter said. "The social and commercial determinants of physical activity are complex and multifaceted, and understanding why some individuals have more opportunities to engage in safe and meaningful physical activity than others warrants further investigation."
Manual occupations are more likely to involve psychosocial stress , lower job control, hazardous working conditions and greater exposure to air and noise pollution, factors that have each been independently linked to dementia risk.
Workers in these roles may also have fewer opportunities for recreational exercise because of fatigue, time constraints or limited access to safe places for physical activity.
The study also found contrasting patterns between leisure-time and occupational activity. Higher levels of leisure-time exercise were associated with progressively lower dementia risk until the benefits leveled off. By comparison, higher amounts of occupational physical activity were associated with progressively greater dementia risk before that association also plateaued.
The authors cautioned that evidence remains limited for both household activity and active commuting, making it difficult to draw firm conclusions about those areas.
Most of the studies included in the analysis were conducted in high-income countries, despite low- and middle-income countries being expected to experience the largest increases in dementia cases in the coming decades.
Another limitation is that nearly all of the studies relied on self-reported physical activity, which can introduce recall bias.
However, Feter said the consistency of the findings across multiple sensitivity analyses suggests the association warrants attention.
Researchers stressed that the results do not mean people should avoid physically active jobs. Because the review was based on observational studies, it cannot prove that occupational activity causes dementia.
Instead, the findings highlight the importance of considering the context in which physical activity takes place. Leisure-time activity remained protective, while occupational activity remained associated with elevated dementia risk, even after accounting for factors including age, education and chronic disease.
The authors also pointed to research published last month in Alzheimer's & Dementia by Raichlen, Feter and colleagues. That study found that mentally active...
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