Slow-Wave Sleep Loss Linked to Increased Dementia Risk in Older Adults"

A 2023 study suggests that the risk of developing dementia increases as people age if they lose even small amounts of slow-wave sleep—the deepest stage of sleep. For individuals over 60, losing just 1% of this type of sleep each year can raise their chances of developing dementia by 27%. The risk is even higher, 32%, when focusing on Alzheimer’s disease.

Slow-wave sleep is the third stage of the sleep cycle, lasting 20–40 minutes and occurring within the 90-minute sleep cycle. It is the most restful stage, where the brain and body undergo essential processes like reduced heart rate, slowed brain activity, and lower blood pressure. During this time, the body strengthens muscles and bones, boosts the immune system, and prepares the brain for learning and memory retention.

Research shows that people with Alzheimer’s-related brain changes who experienced more slow-wave sleep performed better on memory tests. According to neuroscientist Matthew Pase of Monash University, slow-wave sleep helps the aging brain by clearing waste, including proteins that build up in Alzheimer’s disease. Pase and his colleagues examined how slow-wave sleep might influence dementia risk, suggesting that slow-wave sleep loss could be a changeable risk factor.

The study analyzed 346 participants from the Framingham Heart Study, who underwent two sleep studies in 1995–1998 and again in 2001–2003. The participants were followed up until 2018, by which point 52 dementia cases had been recorded. The researchers observed a steady decline in slow-wave sleep after the age of 60, particularly between ages 75 and 80. They found that each percentage decrease in slow-wave sleep per year was linked to a 27% increased risk of dementia.

Slow-wave sleep loss was also linked to cardiovascular disease, medications that impact sleep, and having the APOE ε4 gene, which is associated with Alzheimer’s. The study noted that while the connection between sleep loss and dementia is strong, it doesn’t prove causation. More research is needed to determine whether sleep loss causes dementia or if early dementia processes lead to sleep disturbances.

In the meantime, making sure to get enough sleep—especially slow-wave sleep—can help with memory and overall brain health.

The study was published in JAMA Neurology in November 2023.