New Research Suggests Where Physical Activity Takes Place Could Influence Dementia Risk
Physical activity is widely recognised as an important component of healthy ageing, with previous research linking regular exercise with improved cardiovascular and brain health and a reduced risk of dementia.
However, new research suggests that the context in which physical activity takes place may be just as important as the amount of activity itself.
A systematic review and meta-analysis involving 74 studies and more than 4.2 million adults has found that physical activity undertaken during leisure time was associated with a lower risk of dementia, while high levels of physical activity performed as part of employment were associated with an increased risk.
The findings, published in The Lancet Public Health, indicate that considering all forms of physical activity as equivalent could overlook significant differences in their potential relationship with long-term cognitive health.
Overall, people undertaking high levels of physical activity had an approximately 20% lower risk of developing dementia from any cause. The analysis also found associations with a 21% lower risk of Alzheimer’s disease and a 29% lower risk of vascular dementia.
However, the picture changed when researchers examined the setting in which activity occurred.
High levels of physical activity during leisure time — including exercise and recreational sporting activities — were associated with a 24% lower risk of all-cause dementia.
Household physical activity was also associated with a lower risk, estimated at around 15%, although the researchers stressed that this particular finding was based on only one study and should therefore be interpreted cautiously.
By contrast, occupational physical activity was associated with an estimated 20% higher risk of dementia. Active commuting was also associated with a 10% higher risk, although the evidence supporting both commuting and household activity was limited.
The researchers emphasised that the findings do not demonstrate that physically demanding work causes dementia.
Instead, they suggest that the relationship may reflect the wider circumstances often associated with physically demanding occupations.
People in physically strenuous jobs may experience greater levels of long-term stress, lower job autonomy, hazardous working conditions and exposure to air or noise pollution. Socioeconomic circumstances and other occupational factors could also influence brain health over the course of a lifetime.
The nature of some physically demanding occupations may also involve repetitive tasks with relatively limited opportunities for cognitive stimulation, potentially influencing the development of what researchers describe as cognitive reserve.
The researchers therefore caution against interpreting the results as evidence that physical activity at work is inherently harmful to brain health.
Rather, occupational physical activity may be acting partly as a marker for a combination of social, economic, environmental and workplace factors that can accumulate over many years.
This distinction is particularly important when considering healthy ageing. Someone undertaking regular walking, swimming, gardening, dancing or recreational sport may experience very different physical and psychological circumstances from someone whose employment requires prolonged periods of strenuous manual labour.
The findings add to a growing body of research suggesting that the relationship between physical activity and dementia is more complex than simply measuring how many hours a person spends being physically active.
Previous research has similarly identified an association between sustained high levels of occupational physical activity and later-life cognitive impairment, while leisure-time activity has generally been associated with better cognitive outcomes.
The researchers also identified several important limitations in the evidence.
Most of the studies included in the analysis relied on participants reporting their own levels of physical activity, which can introduce inaccuracies. Furthermore, the certainty of evidence varied between the different activity categories and was generally rated as low or very low.
There was also a geographical limitation: approximately 93% of the studies were undertaken in high-income countries.
That is significant given that the global burden of dementia is expected to grow particularly rapidly in low- and middle-income countries, meaning that further research across a wider range of populations will be needed.
The findings should therefore be viewed as evidence of an association rather than proof that one particular type of physical activity directly causes or prevents dementia.
For care providers and those supporting older people, the research reinforces the importance of taking a broad view of physical activity.
Encouraging residents to remain active through enjoyable, appropriately tailored activities can form an important part of promoting physical and mental wellbeing. Walking, gardening, gentle exercise classes, dancing and recreational activities can all provide opportunities for movement while also supporting social interaction and engagement.
The latest findings suggest, however, that quality, context and purpose may matter alongside quantity when considering physical activity and long-term brain health.
They also underline the need for further research to understand why different forms of activity appear to have contrasting associations with dementia risk, and how factors such as occupation, socioeconomic circumstances, stress, environmental exposures and cognitive stimulation interact over the life course.
The research does not change the established message that staying physically active is an important part of healthy ageing. Rather, it suggests that when considering dementia prevention, not all physical activity should necessarily be viewed through the same lens.
