The Critical Link Between Sleep and Brain Health
Humans have been pushing the natural boundaries between day and night for centuries. In the 1800s, we used candles and gas lamps to extend the day. Today in America, you can go for a meal, exercise at the gym, or shop for groceries at almost any time during a 24-hour cycle. There are plenty of opportunities to stay awake.
Making sleep a priority, however, is another matter. A majority of Americans report sleeping poorly and many more convince themselves they don’t need much sleep. But they’d be wrong. When sleep experts say we need seven to nine hours of sleep, they know what they’re talking about. And new research suggesting that the brain uses sleep time to clear away harmful neurotoxins makes it even more critical.
In the last couple of decades, big strides have been made in sleep research. Scientists have learned that we use sleep to regenerate our cells, practice skills and consolidate memories. They also found that energy consumption within the brain didn’t fluctuate much between wakefulness and sleep, which didn’t make sense. Many neural functions shut down at night so why didn’t energy consumption decrease during sleep?
A team of researchers at the University of Rochester Medical Center’s Center for Translational Neuromedicine, led by co-director Maken Nedergaard, think they have the answers. Through advanced brain-imaging technology, they observed the sleeping brains of mice, which are strikingly similar to humans’. They discovered what they call the glymphatic system, which cleans the brain and rids it of harmful toxins. It works like a trash removal company, rumbling around the neighborhood, picking up trash and dumping it in a landfill (which turns out to be the liver). It pumps cerebrospinal fluid (CSF) throughout the brain, whose cells, during this process, contract and shrink by up to 60 percent! This contraction allows the CSF to flow more freely, consequently doing a more thorough job. The team found that the glymphatic system is close to 10 times more active during sleep than it is during wakefulness and was the cause of all that energy usage. Working with limited resources, the brain chooses to perform this vital purge during sleep rather than when we’re awake, doing all our “stuff.”
The big headline from this research is that the toxins being cleared from our brain include amyloid-beta, thought to be responsible for Alzheimer’s disease. If we don’t get enough sleep, these and other neurotoxins accumulate where they can cause serious, long-term damage. And if you need more motivation to reform your sleep habits, people with sleep deficits are more likely to be depressed, be obese, develop diabetes, have a weaker immune system, and age prematurely.
Click to access a sleep diary created by the National Sleep Foundation.