The team was led by Matthew Walker, professor of neuroscience and psychology and head of the Sleep and Neuroimaging Laboratory at Berkeley. Sleep is vital to all animals, says Walker — every single bodily system relies on that downtime to function properly.
The Berkeley team reviewed the sleep data of 2 million people and noticed changes in the sleeping patterns over different age ranges. Then they examined the sleeping patterns and neurological impulses of rodents.
Walker's team found that the chemical signal that triggers sleep in the brains of mice declines in strength as the mice get older. The brain has a more difficult time receiving the signal as a result, making it more difficult for the older mice to sleep for a longer period of time.
"It's almost like a radio antenna that's weak," said Walker in a statement. "The signal is there, but the antenna just can't pick it up." Walker believes that this is a sign that sleep deprivation contributes to aging, whereas conventional wisdom had it the other way around.
"Or at least it's a two-way street I think, and maybe the fact that it's flowing in more than one direction. In other words, I think sleep disruption is a novel, underappreciated fact that is contributing to age and dementia as we get older," he said.
When you fall asleep, you cycle between four states. One of those states is called Slow Wave Sleep (SWS), and its purpose is to recuperate the brain and body. Older people take a longer time to fall asleep and awaken more often, but most importantly, they spend less time in the SWS state.
Sleep decline typically begins in the late 20's or early 30's and continuously decreases. By the time the average person turns 50 their sleep becomes half as restful as it was when they were 20. This is why older people frequently wake up throughout the night while young people sleep like rocks.
A good night's rest is more important than just avoiding crankiness and coffee addiction, according to Walker. "Every one of the major diseases that are killing us in first-world nations – from diabetes to obesity to Alzheimer's disease to cancer – all of those things now have strong causal links to a lack of sleep. And all of those diseases significantly increase in likelihood the older that we get, and especially in dementia."
Now that the problem is better understood, Walker says, it may be possible to treat it. Currently, there's no drug that targets the brain's "sleepiness receptor." Sleeping pills and other sedatives may make it easier to fall and stay asleep, but they don't improve the amount of SWS that the body needs.
Two promising techniques that Walker hopes to explore in successive research are electrical brain stimulation, which is invasive but has proven effective in improving the quality of sleep among young people, and cognitive behavioral psychotherapy, which has been used as an insomnia treatment in the past.
"Sleep decline is one of the most dramatic physiological changes that occurs as we age, yet that demonstrable change is not part of the health conversation today," said Walker.
"We need to recognize the causal contribution of sleep disruption in the physical and mental deterioration that underlies aging and dementia. More attention needs to be paid to the diagnosis and treatment of sleep disturbance if we are going to extend healthspan, and not just lifespan."
In 2016, policy think tank RAND Corporation estimated that the loss of productivity caused by Americans not getting enough sleep costs $411 billion every year.