This conclusion was reached by an international group of scientists who analyzed the results of 74 observational studies. In total, they covered more than 4.2 million people aged 45 to 93 from 30 countries. The work was published in the journal *The Lancet Public Health*. ## The Paradox of Physical Activity Previously, physical activity was often viewed as a single indicator: the more a person moves, the better it is for their health. However, the new analysis showed that leisure-time activity and physical labor at work may be associated with the risk of dementia in different ways. > "We have long known that physical activity is generally associated with a lower risk of dementia, but most studies have treated all types of movement as the same," explained one of the authors, Nathan Fether from the University of Southern California. It is the differences between voluntary activities and forced labor that the researchers referred to as the "paradox of physical activity." ## What Proved to be Beneficial A high level of leisure-time activity was associated with a reduction in the risk of dementia by about 24%. This type of activity includes walking, swimming, running, dancing, gym workouts, and cycling for leisure or training. Performing household chores was found to be associated with a risk reduction of about 15%. At the same time, the principle of "the more, the better" only works up to a certain point. As leisure-time activity increased, the risk gradually decreased, but then the effect plateaued. It is likely that not only the movement itself matters. Voluntary activities usually allow a person to choose the pace, duration, and rest time. Additionally, sports and walks can be accompanied by social interaction, emotional relief, and additional mental stimulation. ## Why Physical Labor Does Not Have the Same Effect High physical activity at the workplace, on the contrary, was associated with approximately a 20% increase in the risk of dementia. The heavier and longer the load, the more pronounced this association was. Scientists emphasize that the cause may not be physical labor itself, but the accompanying conditions: * chronic stress; * low wages; * insufficient recovery time; * exposure to noise and polluted air; * monotonous repetitive movements; * lack of mental stimulation; * socio-economic differences among participants. In other words, an eight-hour heavy shift and a half-hour walk after work affect the body differently, even if in both cases a person is moving a lot. ## An Unexpected Result for Commuting Active commuting—long walking or cycling—was associated with an approximately 10% increase in the risk of dementia. However, this result should be evaluated with particular caution: the conclusion is based on only two studies, so it cannot yet be considered definitive. Possible explanations include air pollution, stress, lack of free choice, and socio-economic characteristics of the participants. This does not mean that walking or cycling is harmful. Rather, the study shows that the same activity can occur under completely different conditions and be accompanied by various risk factors. ## Correlation Does Not Imply Causation The authors emphasize: the analysis included observational studies, so it does not prove that heavy physical labor directly causes dementia. It only shows a statistical correlation. The likelihood of developing dementia is influenced by age, genetic predisposition, education, cardiovascular health, nutrition, smoking, sleep quality, social activity, and many other factors. Additionally, people engaged in heavy physical labor may more frequently encounter adverse living conditions that are difficult to completely separate from the influence of the labor itself. Even for someone with physically demanding work, it is beneficial to find time for voluntary and enjoyable activities—walking, swimming, dancing, or other suitable pursuits. The study does not negate the benefits of movement but shows that for brain health, it is important to consider not only the volume of activity but also stress, working conditions, recovery opportunities, and personal choice.
