The link between movement and brain health has never been clearer. Two recent studies, published in The Lancet Public Health and PLOS One, shed light on one of modern medicine's most pressing questions: how to prevent dementia, a disease already affecting 55 million people worldwide, with projected costs reaching €2 billion by 2030.
It's Not Just How Much You Move, But How and Why
The first study, led by the University of Southern California, analyzed data from 74 studies involving more than 4.2 million people across 30 countries, aged 45 to 93, and followed participants for an average of 10 years.
The findings, published in The Lancet Public Health, confirm the so-called physical activity paradox: while recreational exercise – walking, running, cycling, swimming, or playing sports – reduced dementia risk by 24%, occupational physical activity (jobs requiring physical effort) was associated with a 20% higher risk.
“These findings challenge the long-held assumption that all movement counts for brain health,” noted Natan Feter, first author of the study. Context is key: recreational exercise is typically self-directed, done at an enjoyable intensity, and often accompanied by social interaction. In contrast, manual occupational effort includes repetitive tasks, long hours on your feet, heavy lifting, little recovery time, and greater exposure to adverse environmental factors such as noise or pollution.
What is the physical activity paradox?
This concept describes how the same type of activity (physical exertion) can have opposite effects on health depending on its context. Leisure exercise brings cardiovascular and mental benefits, while sustained occupational effort without adequate recovery can lead to chronic stress and poorer overall health.
Sleep and Sedentarism Also Play a Role
The second study, from York University (Canada), published in PLOS One, reviewed 69 studies involving millions of adults over 35 years old. They found that regular physical activity was linked to a 25% lower dementia risk, and that sleeping 7–8 hours per night also offered protection.
Conversely, sleeping less than 7 hours raised dementia risk by 18%, and sleeping more than 8 hours increased it by 28%. Sitting for more than 8 hours daily raised risk by 27%.
What Does This Mean for Daily Life?
The authors recommend prioritizing physical activity during leisure time, as well as improving access to parks and safe spaces, ensuring adequate rest, and reducing harmful exposures in the workplace. “The context in which physical activity is performed can be as important as the activity itself,” highlighted David Raichlen.
Professor Lucrecia Moreno, from CEU Cardenal Herrera University, points out the importance of the cognitive reserve: if your job is physically demanding, it's crucial to maintain mental stimulation; if your job is sedentary, don't underestimate the value of physical exercise.
| Factor | Effect on Dementia Risk |
|---|---|
| Recreational exercise | -24% risk |
| Occupational physical activity | +20% risk |
| Regular physical activity | -25% risk |
| Sleeping 7–8 hours/night | -25% risk |
| Sleeping < 7 hours/night | +18% risk |
| Sleeping > 8 hours/night | +28% risk |
| Sitting > 8 hours/day | +27% risk |
Sources: elEconomista.es · Infobae · Cuídate Plus · Diario de Cuyo · Agencia SINC