A large-scale analysis led by researchers at York University in Canada suggests that sleep habits, physical activity, and daily sitting time play a significant role in the risk of developing dementia. Reviewing data from 69 studies involving nearly four and a half million people, the researchers found that sleeping between seven and eight hours per night was associated with the lowest risk of dementia. Sleeping less than seven hours increased risk by about 18 percent, while sleeping more than eight hours raised the risk by about 28 percent.

The findings indicate that both insufficient and excessive sleep may be linked to poorer brain health. However, the researchers stress that the results show statistical associations rather than direct cause and effect. In some cases, prolonged sleep may be an early sign of neurodegenerative diseases rather than a direct cause.

Beyond sleep, sitting for more than eight hours a day and engaging in less than 150 minutes of physical activity per week were also linked to higher dementia risk. The researchers estimate that up to half of dementia cases could be prevented or delayed through lifestyle changes, emphasizing that balanced sleep, regular movement, and reduced sitting time may help protect cognitive health over time.