Getting less than 6 hours of sleep during middle age dramatically increases risk of dementia

LONDON — At any age, the benefits of a full night’s sleep can be tremendous for human health. While the common belief is everyone needs eight hours of rest, studies point to six or seven being good enough. Now, a new report finds those hours of sleep are even more important than ever for people during middle age. Researchers from University College London say getting less than six hours of nightly rest in your 50s and 60s significantly increases the chances of developing dementia later on.

Their findings reveal middle-aged individuals sleeping less than six hours a night are 30 percent more likely to develop dementia. Around five million Americans over age 65 are dealing with some form of cognitive decline. The CDC expects that number to rise to 14 million by the year 2060.

“Sleep problems are known to occur in people with dementia, but it remains unclear whether sleep duration in midlife affects the risk of developing dementia at older ages. Here, by using a very long follow-up period, we have found that short duration sleep in midlife, assessed more than 25 years before mean age at dementia onset, is associated with dementia risk in late life,” says lead author Dr. Séverine Sabia in a university release.

“While we cannot confirm that not sleeping enough actually increases the risk of dementia, there are plenty of reasons why a good night’s sleep might be good for brain health. These findings confirm the importance of sleep hygiene for health.”

Your sleep history may increase dementia risk

Researchers find growing evidence that a person’s sleep patterns long before the onset of dementia symptoms contributes to the disease. Insufficient sleep duration is already a dementia risk factor among seniors 65 and older. However, the British team now believes this may have more to do with bodily changes starting at younger ages.

Study authors examined data on 7,959 British adults from the Whitehall II cohort study during their review. Participants self-reported their sleep durations six times between 1985 and 1988, while the group was between ages 35 and 55. They then documented their sleep length again between 2015 and 2016, now between the ages of 63 and 86.

Researchers say the readings allowed them to see sleep duration patterns at ages 50, 60, and 70. Some of the participants also wore watch accelerometers over a full week to provide objective measurements of their sleep length. Over the course of this 30+ year study, 521 participants developed dementia by 2019.

The results reveal sleep duration during middle age has a strong connection to who suffers from cognitive decline later on. Specifically, less than six hours of sleep each night during midlife significantly elevated each participant’s dementia risk.

Does getting extra sleep help?

Researchers note that there doesn’t appear to be any link between sleeping more than eight hours and lower dementia risk. Previous studies suggest too much sleep also increases dementia risk, but the new report finds those results to be inconsistent.

The team also reveals the link between sleep and dementia is independent of other factors like mental health, behavioral differences, sociodemographic status, and heart health.

“We know that sleep is important to our brain health, as it is involved in learning and memory, waste clearance from the brain, and the ability of our brain cells to remain healthy. A better understand of how sleep features might shape our risk of dementia is needed, as this might help researchers develop new ways to reduce the risk of dementia, or to delay its progression,” concludes senior author Dr. Archana Singh-Manoux.

The study appears in the journal Nature Communications.