New research highlights a growing concern for brain health: sitting for extended periods each day may significantly increase the risk of dementia.
According to a large-scale review published in PLOS One, adults aged 35 and older who sit for more than eight hours daily face a 27% higher risk of developing dementia compared to those who sit less. The findings stem from an analysis of nearly 300,000 participants in long-term prospective studies conducted by researchers at York University in Canada.
The study also underscores the critical role of sleep duration in cognitive health. Analyzing data from over 1.3 million individuals across 17 sleep studies, researchers found that both insufficient and excessive sleep are linked to elevated dementia risk. Compared to individuals who consistently sleep seven to eight hours per night — considered the optimal range — those who sleep less than seven hours face an 18% increased risk, while those who sleep more than eight hours see a 28% rise in risk.
Experts explain that disruptions to sleep and prolonged inactivity may impair the brain’s glymphatic system, which is most active during sleep and helps clear metabolic waste and regulate inflammation. When this system is compromised, the aging process in the brain may accelerate, potentially contributing to structural decline and neurodegeneration.
Researchers emphasize that regular physical activity remains one of the most effective strategies for protecting brain health. They recommend breaking up long periods of sitting with movement and maintaining consistent, moderate sleep patterns to support long-term cognitive resilience.
As global populations age, dementia continues to pose a major public health challenge. Current estimates suggest approximately 55 million people worldwide live with dementia, a number projected to triple by 2050. Addressing modifiable lifestyle factors like sedentary behavior and sleep hygiene could play a key role in reducing future burden.
