A statistical analysis pooling data from 69 previous studies has identified 7 to 8 hours of nightly sleep as the optimal duration for minimizing dementia risk, ScienceAlert reported. Researchers at York University in Canada examined this sleep window alongside physical activity and sedentary time as modifiable lifestyle factors that could potentially prevent or delay the onset of dementia.
Abnormal sleep durations increase dementia risk
The York University researchers found that sleeping less than 7 hours each night correlated with an 18 percent increase in dementia risk, while logging more than 8 hours correlated with a 28 percent increase. The review encompassed nearly 4.5 million participants starting from a dementia-free baseline, tracking disease incidence over time across populations aged 35 and older. While the study established strong statistical associations, the authors emphasized it does not prove direct cause and effect, noting that prolonged sleep can sometimes serve as an early sign of Alzheimer’s disease rather than its driver.
Increased REM sleep lowers disease risk
Expanding on sleep quality metrics, a separate study published in PLOS Medicine analyzed wrist accelerometer data from over 95,000 UK Biobank participants followed for roughly nine years. That study found that getting more REM sleep was associated with a lower risk of 83 different diseases, including a 46 percent lower risk of dementia. Participants who logged about 47 more minutes of REM sleep showed these reduced risk associations, while greater deep sleep was linked to a lower risk of seven conditions, including type 2 diabetes and Parkinson’s disease. Experts note that consumer fitness trackers estimate these sleep stages using algorithms rather than clinical overnight sleep studies, meaning users should focus on total duration and consistent schedules rather than chasing specific wearable scores.
Sedentary Behavior and Physical Activity
Alongside sleep duration, the York University analysis evaluated physical movement and sitting time. Prolonged sitting exceeding 8 hours a day and a lack of physical activity falling below 150 minutes a week both correlated with a significant increase in the chances of developing dementia. Only 3 of the 69 studies reviewed specifically examined sedentary habits, pointing to a need for further research involving middle-aged adults and long-term behavioral changes.
Sleeping seven to eight hours minimizes dementia risk
What did the York University study reveal about sleep and dementia?
The analysis of 69 studies covering nearly 4.5 million participants found that sleeping 7 to 8 hours nightly minimized dementia risk. Sleeping less than 7 hours was linked to an 18 percent higher risk, while sleeping more than 8 hours was linked to a 28 percent increase.
How does REM sleep relate to disease risk according to UK Biobank data?
Research published in PLOS Medicine utilizing data from over 95,000 participants tracked via wrist accelerometers showed that getting about 47 more minutes of REM sleep was associated with a 46 percent lower risk of dementia and reduced risk across 83 total diseases.
What physical activity and sitting thresholds were analyzed?
The York University researchers found that sitting for more than 8 hours a day combined with physical activity of less than 150 minutes a week significantly increased the likelihood of developing dementia.
Related reading