Sleeping too long is bad for the brain, you should not exceed this number of hours per night

Some people need more sleep, which is not without health risks.

We spend about a third of our lives sleeping. The French sleep an average of 7 hours a day, and many of them suffer from sleep debt, the consequences of which are well-known for their health. But conversely, some are "heavy sleepers" and need more sleep than others. This is also not insignificant for health, especially for the brain.

Needing more sleep per night is a real sleep disorder called hypersomnia. This rare disorder has short-term consequences: fatigue, difficulty concentrating, memory problems, decreased intellectual capacity... But it also has long-term consequences. Excess—as well as lack—of sleep can be the cause of several chronic diseases, including obesity and cardiovascular disease.

Studies have shown that sleeping more than 9 hours a night also has an impact on the brain, beyond mental health. "Several studies have suggested that excessive or insufficient sleep is linked to deficiencies in cognitive domains, including memory, attention, and the ability to manage and direct other mental processes, such as planning, problem-solving, and impulse control," explained American researchers who have researched the subject in a press release.

Their work, published this year, rightly suggested that "sleeping nine hours or more per night is associated with poorer cognitive performance, particularly in people with depression," whether or not they take antidepressants. These people are very often affected by sleep disturbances, including an excessive need for sleep. Depression is also an established risk factor for cognitive decline, including dementia. "Sleep may be a modifiable risk factor for cognitive decline in people with depression," according to Vanessa Young, the lead author of the American study.

Another study published in 2017 in the journal Neurology concluded that people who sleep too much are twice as likely to develop dementia. "Extended sleep duration may be a marker of early neurodegeneration and therefore a useful clinical tool for identifying individuals at higher risk of progressing to clinical dementia within 10 years," the researchers said.

It may be normal to need more sleep at certain times in life, particularly during childhood or in the event of illness, but a chronic need to sleep more than 9 hours per night in adults, especially in the event of daytime symptoms such as fatigue, should lead to consulting a health professional who can establish the cause of this hypersomnia and put treatments in place.