A new large-scale analysis suggests that both insufficient and excessive sleep, along with prolonged sitting, may significantly increase the risk of dementia. The findings highlight the importance of balancing daily habits such as physical activity, sleep, and sedentary time for better brain health.

Dementia affects more than 55 million people worldwide and currently has no cure, making prevention strategies especially important. Researchers emphasize that modifiable lifestyle factors—like how much people move, sit, and sleep—are among the most promising areas for reducing risk.

The study combined data from 69 previous studies involving adults aged 35 and older. It found that regular physical activity was associated with a 25% lower risk of dementia, reinforcing its key role in maintaining brain health across different age groups.

Sleep duration also showed a strong connection to dementia risk. Sleeping less than seven hours per night was linked to an 18% higher risk, while sleeping more than eight hours increased risk by 28%. These results suggest that consistently sleeping outside the recommended 7–8 hour range may have long-term consequences for cognitive health.

Sedentary behavior was another important factor. Spending more than eight hours a day sitting was associated with a 27% higher risk of dementia. Researchers note that prolonged, uninterrupted sitting may negatively affect the brain, even in people who are otherwise physically active.

Experts stress that breaking up long periods of sitting, staying active, and maintaining regular sleep patterns are practical, low-risk strategies that may support cognitive health. However, since the findings are based on observational data, more research is needed to confirm cause-and-effect relationships.

Overall, the study suggests that small, consistent lifestyle changes—such as incorporating movement into daily routines, improving sleep habits, and reducing sedentary time—may play an important role in lowering dementia risk over time.