We all know that we're supposed to rest when we're sick, but let's face it: few of us do.
With the flu still surging above epidemic levels, we talked to two sleep experts to explain the science behind the immune and restorative properties of sleep. Dr. Stuart Quan is the clinical chief and medical director of Brigham and Women's Hospital Sleep Disorders Service, and Bob Rosenberg is the medical director of the Sleep Disorders Center of Prescott Valley, Arizona, and author of Sleep Soundly Every Night; Feel Fantastic Every Day.
Sleep probably gets less credit than it should for battling illness since much of its work is under cover, so to speak: sleep is essential to your immune system in warding off sickness before you can sniffle.
A 2012 study on responses to vaccines illustrates exactly how closely sleep is linked to the immune system: Researchers found that those who got the hepatitis B vaccine after sleeping fewer than six hours that week were much more likely to be unprotected from the disease six months later. And each extra hour of sleep correlated with a 56 percent increase in secondary antibody levels, they reported in the journal SLEEP.
Previous laboratory studies showed similar results with the flu vaccine.
What scientists don't know for certain is just how sleep confers its benefits. It's likely, though, that inadequate sleep affects the number and type of immune cells in your body. T-cells, for example, help prevent infection, but their numbers fall with sleep deprivation, Quan said.
Lack of sleep can also mess with concentrations of cytokines, proteins that signal cells, resulting in a less-than-adequate antibody response. It may take as little as a single night to prompt those responses.
"One night of bad sleep can make a lot of difference," Quan said.
And chronic lack of sleep may manifest itself as unexplained aches and pains, Rosenberg said, referring to a study in which severely sleep-deprived college students reported symptoms similar to fibromyalgia.
Sleep is equally essential in helping you recover if you do get sick, Rosenberg said.
"Sleep is important for healing because slow wave or deep sleep is when tissue repair occurs," Rosenberg said. "We put out most of our growth hormone in deep sleep, and growth hormone is important in terms of repairing tissue, muscle, everything you could think of that has to do with repair."
Most of us are conditioned to fight or ignore sickness, putting off resting by working at home or muddling through a day at the office.
"We look at sleep as a hindrance rather than an important time of restoration and brain growth," Rosenberg said.
The vast majority of us need between seven and nine hours of sleep a night. Chronic sleep deprivation usually refers to fewer than six hours, Rosenberg said. When we're sick, that number may shift, so it's especially important to listen to your body. The good news is that our bodies clue us in by making tumor necrosis factor alpha (TNF) proteins, which trigger sleepiness and fatigue, when we're ill.
"Many think that may be protective," Rosenberg said, so "ride with it. The bottom line is if you're sleepy or fatigued, get sleep and rest -- that's what your body is telling you."