Apr 27, 2026 12:00:00

The optimal amount of sleep to reduce the risk of dementia has been revealed.

With dementia cases on the rise worldwide, scientists are searching for ways to prevent its onset. Previous research has indicated that

people who get too little sleep are at higher risk of dementia, but a new study analyzing data from over 1.3 million people has revealed the 'optimal amount of sleep to reduce dementia risk.'

The Relationships between physical activity, sedentary behavior, sleep, and dementia: A systematic review and meta-analysis of cohort studies | PLOS One
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0343621

Scientists Reveal The Optimal Amount of Sleep to Lower Dementia Risk : ScienceAlert
https://www.sciencealert.com/scientists-reveal-the-optimal-amount-of-sleep-to-lower-dementia-risk

Since there is no established cure for dementia, preventing its onset is crucial. Dementia caused by Alzheimer's disease and other conditions is known to be associated with various risk factors such as exercise habits, diet, social isolation, sleep duration, air pollution, and hearing impairment.

A research team at York University in Canada integrated data collected from 69 previous studies to analyze the relationship between three factors—physical activity, sleep duration, and sedentary time—and the risk of dementia. The analysis of dementia risk and physical activity involved data from over 2.8 million people, the analysis of sleep duration involved over 1.3 million people, and the analysis of sedentary time involved over 290,000 people.

The analysis revealed that getting less than 7 hours of sleep per night increased the risk of dementia by approximately 18%, while getting 8 hours or more of sleep per night increased the risk by approximately 28%. In other words, the optimal amount of sleep to reduce the risk of dementia is 7 to 8 hours per night.

These results are consistent with previous research indicating that people who sleep too much are more likely to have poor health and a higher risk of death. Possible reasons for this include the fact that 'people with poor health to begin with need more sleep to recover' and 'the deterioration of health leads to a decline in sleep quality.'

Why are people who sleep too much at a higher risk of death? - GIGAZINE

The study also found that a sedentary lifestyle of more than eight hours a day and less than 150 minutes of exercise per week significantly increase the risk of dementia. In their paper, the research team states, 'Regular exercise, reduced sedentary time, and adequate sleep (7-8 hours) may be associated with a reduced risk of dementia and could be achievable factors in preventing or delaying the onset of dementia.'

This study merely investigated the relationship between dementia risk and three factors, and did not experimentally confirm a causal relationship. However, the research team argued that exercise and sleep may maintain active blood flow in the brain, remove waste products from nerve cells, and protect brain-related areas such as the heart.