August 20, 2026
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Work that requires physical activity may increase the risk of dementia, a new study finds.
The benefits of physical activity are well known, from improved mood and sleep to better brain health and increased longevity, so it would seem that more movement is always good.
But a new study challenges this thought, at least when it comes to dementia risk, and renews focus on what is known as the "physical activity paradox."
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The physical activity paradox is the hypothesis that exercise done during down time benefits overall health, while exercise done as part of a job may not yield the same positive effects and may actually be detrimental.
Prior research lends support to the physical activity paradox as it relates to cardiovascular risk and death from all causes.
A 2021 paper, for instance, found that higher activity during leisure time was associated with reduced risk of heart attacks, stroke and all-cause mortality, but that physical activity on the job was linked to an increase in these risks. A 2018 meta-analysis of 26 different studies also found that, for men, a higher level of physical activity was associated with an increased risk of death from any cause, regardless of level of leisure-time activity.
The new study, published Tuesday in The Lancet Public Health, looked more specifically at the impact of work-related physical activity and dementia risk. The findings suggested that leisure-time activities, such as swimming, running, walking and playing sports, was associated with a decreased risk of dementia but that physical activity on the job increased dementia risk.
"The findings challenge the long-held assumption that 'every move counts' for brain health," said Natan Feter, the study's first author and a postdoctoral fellow at the University of Southern California.
The study analyzed 74 studies involving 4.2 million people, ages 45 to 93, in 30 countries. The researchers tracked participants' diagnoses for dementia and Alzheimer's disease.
People who engaged in higher levels of physical activity off the job had a 24% lower risk of dementia than people who were least active. But people who engaged in occupational physical activity had a 20% higher risk of dementia.
"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," Feter told Newsweek.
Another possible explanation for the findings is that on-the-job physical activity may involve heavy lifting, repetitive motions and other forms of movement that can be damaging to the body. Also, these types of jobs may deplete people's energy, making it harder for them to engage in leisure time physical activities, the researchers said.
