Americans are one sleep-deprived population – only a third of us get the minimum seven hours of sleep a night. But it’s not all about quantity of sleep, quality also matters. In a recent study, researchers found that people who get less quality sleep are at higher risks for developing dementia.
In the new study, researchers collected sleep data on over 300 people, whose ages averaged to 67 year. The participants were followed for an average of 12 years. By that point, about 10 percent of the group (32 people) were diagnosed with some form of dementia. Alzheimer’s disease accounted for 75 percent of that subset.
When the researchers compared the dementia diagnosis with the person’s sleep profile, they noticed a striking pattern. Those who got less REM sleep seemed to have an increased risk of developing cognitive problems later in life.
REM, or “rapid eye movement,” refers to one of the five stages of sleep, and is characterized by quick, random movements of the eyes. When people enter this stage of sleep, the brain’s electrical output actually resembles wakefulness, marked by high activity. This is why REM sleep is sometimes referred to as “paradoxical” sleep. People are most likely to experience vivid dreams in REM sleep.
Scientists have known for years that lack of sleep is a major contributor to health problems. But this is one of the first studies to point to a correlation between poor sleep and increased dementia risks. It’s important to note that the results do not suggest cause and effect; rather, there is a link between low REM sleep and dementia risks.
In a typical night people cycle through the sleep stages about four to five times, with each subsequent cycle lasting longer than the previous. However, over the course of the average human lifespan, REM sleep duration shortens progressively. That is, a newborn baby spends about 80 percent of the total sleep time in REM, while in the average adult, REM sleep only accounts for 20 to 25 percent of our total sleep time.
By comparison, people in the study who developed dementia spent about 17 percent of total sleep time in REM. While the difference may seem small, the team found that every 1 percent of reduced REM sleep was correlated to a 9 percent increase in dementia risks.
It’s thought that REM sleep helps the brain process and consolidate memories and experiences. Some studies also implicate REM sleep in promoting healthy neural networks, and the development and maintenance of a healthy brain. Given these roles, it’s not inconceivable that not getting enough quality REM sleep is tied to cognitive decline.
"On one hand, REM may help protect connections within the brain that are vulnerable to damage with aging and Alzheimer's disease," said Matthew Pase, a senior research fellow at Swinburne University of Technology in Australia. "On the other hand, perhaps lower REM is caused by other potential dementia risk factors, such as heightened anxiety and stress. This requires further study."
One bright note is that non-REM sleep was not associated with dementia risks.
Next, the team plans to confirm the effect in a larger sample. Moreover, they hope future experiments may point to a mechanism of how dementia is tied to poor sleep. Such knowledge could facilitate big prevention efforts for this debilitating disease.
Additional sources: Live Science
