Optimal sleep duration to reduce risk of dementia identified

Sleeping seven to eight hours a night is associated with the lowest risk of developing dementia. Both too little and too much sleep were associated with an increased risk of disease. This conclusion was reached by scientists at York University in Canada. The results of their study were published in the journal PLOS One.

The authors analyzed data from 69 previous studies that included a total of nearly 4.5 million people. In addition to sleep duration, the researchers assessed the effects of physical activity and time spent sitting.

Compared to the optimal seven to eight hours, sleeping less than seven hours a night was associated with an 18 percent increased risk of dementia. People who slept more than eight hours had a 28 percent higher risk.

Additional risk factors were lack of movement and prolonged sitting. Less than 150 minutes of physical activity per week and more than eight hours of sedentary activity per day were also associated with a greater likelihood of developing dementia.

The authors note that sleep, movement, and physical activity can support blood flow to the brain, normal nerve cell function, and reduce inflammation. However, the study found an association, but did not prove that too little or too much sleep directly causes dementia.