Summary: People who perform physically demanding jobs face a 55% higher risk of developing dementia compared with those in more sedentary occupations.
Source: University of Copenhagen
A new study from the University of Copenhagen finds that long-term, hard physical work is linked with a substantially higher risk of dementia. After adjusting for lifestyle factors and other relevant variables, men who performed physically demanding jobs had about a 55% greater risk of developing dementia than men in sedentary roles.
While regular leisure-time physical activity is widely recognized as protective against cognitive decline, this study highlights a crucial distinction: not all physical activity produces the same health effects. Occupational physical activity—repetitive, strenuous labor performed over many years—appears to have different consequences for brain and cardiovascular health than voluntary exercise done in free time.
Associate Professor Kirsten Nabe-Nielsen from the Department of Public Health at the University of Copenhagen, who led the research in collaboration with the National Research Centre for the Working Environment and Bispebjerg-Frederiksberg Hospital, emphasizes that the form and context of physical activity matter.
“We expected that heavy physical work might increase dementia risk. Previous studies have suggested this possibility, but our investigation is the first to link occupational physical strain convincingly with a higher occurrence of dementia,” says Kirsten Nabe-Nielsen. She explains that public health recommendations about physical activity should distinguish between exercise taken voluntarily in leisure time and the strenuous physical demands of many occupations, since they may produce opposite effects on long-term brain health.
Even after accounting for smoking, blood pressure, body weight, alcohol consumption and leisure-time exercise, the association between heavy physical work and higher dementia incidence persisted. This suggests occupational strain may independently contribute to the development of dementia.
Professor MSO Andreas Holtermann of the National Research Centre for the Working Environment, a co-author of the study, stresses the importance of prevention. “Changes in the brain linked to dementia begin many years before people retire. Workplace measures to promote health are valuable, but they are often taken up more by better-educated employees. Those with shorter education and manual jobs—despite higher daily step counts and more body use—tend to have poorer fitness, more pain and higher rates of overweight. For many manual workers, avoiding heavy lifts alone is not enough if they want to stay in the workforce into older age. They need preventive strategies such as targeted exercise and strength training to build physical resilience.”
The analysis draws on the Copenhagen Male Study (CMS), which followed 4,721 Danish men who reported their typical work tasks in 1970–71 when they were 40–59 years old. The original cohort came from 14 large Copenhagen-based employers, including national services and municipal workplaces. Over decades of follow-up, researchers collected health information on these men and linked it to national registers to identify dementia diagnoses.
The study team suggests biological mechanisms that could explain the link between physically demanding work and dementia. Prolonged physical strain may negatively affect cardiovascular function and blood supply to the brain, contributing to high blood pressure, heart disease, and other vascular conditions that increase dementia risk.
Following these findings, the National Research Centre for the Working Environment is collecting additional data from occupations such as social and healthcare assistants, childcare workers and packing operatives. The goal is to design workplace interventions that reorganize physically demanding tasks so they deliver an “exercise effect” rather than cumulative wear and tear. Such interventions aim to make heavy lifts and repetitive tasks healthier for workers by incorporating strength training, recovery periods and ergonomic changes.
Researchers hope employers will adopt practical changes that enable manual workers to remain healthier longer, and that occupational health guidance will differentiate clearly between beneficial leisure-time physical activity and potentially harmful occupational physical strain.
About this dementia research news
Source: University of Copenhagen
Contact: Kirsten Nabe-Nielsen – University of Copenhagen
Image: The image is in the public domain.
Original Research: Closed access.
“The effect of occupational physical activity on dementia: Results from the Copenhagen Male Study” by Kirsten Nabe-Nielsen et al. Scandinavian Journal of Medicine & Science in Sports. DOI: 10.1111/sms.13846
Abstract
The effect of occupational physical activity on dementia: Results from the Copenhagen Male Study
Leisure-time physical activity (LTPA) reduces the risk of dementia, while the effect of occupational physical activity (OPA) remains uncertain. This longitudinal analysis used self-reported data on OPA and LTPA collected in 1970–71 from 4,721 male employees aged 40–59 at baseline. Dementia cases were identified through national registers, and participants were followed from age 60 until 2016. Incidence rate ratios (IRR) were estimated and adjusted for age, socioeconomic status, marital status, and psychological stress. Additional models included health behaviors and blood pressure, and mutually adjusted OPA and LTPA. During 86,557 person-years of follow-up, 697 dementia cases were identified. Participants with high OPA had an adjusted IRR of 1.48 (95% CI: 1.05–2.10) compared with men in sedentary jobs. High LTPA was associated with a non-significantly lower IRR of dementia compared with sedentary leisure time. The study concludes that LTPA and OPA are differentially associated with dementia risk, indicating that current recommendations about physical activity and dementia prevention should explicitly refer to leisure-time exercise; further research on occupational physical activity and cognitive health is warranted.