It's common knowledge that sleep is essential to staying healthy. Even still, too many adults fail to get enough each night. Constant sleep deprivation not only causes zombie-like behavior; over time it also weakens the immune system and raises a person's risk for a number of chronic health conditions, including diabetes, obesity, heart disease and stroke. Poor sleep hygiene can also be a contributing factor for heightened depression risk and affects a person's ability to think, focus and make decisions.
A new study published Monday in the journal Sleep finds people who don't sleep enough are at higher risk for developing colds. Most studies that seek to understand the link between sleep and immune system function are based on forced sleep deprivation of participants. But this study sought to emulate real-life scenarios and provide a more nuanced understanding of the health impact of staying in bed one or two hours longer each night.
For the study, 169 adults underwent health screenings for two months, including questionnaires about lifestyle habits such as cigarette and alcohol use, stress levels and even their personality and temperament. Participants wore wristwatches that monitored sleep quality and quantity over the course of a week. Next, each person checked into a hotel and received nasal drops that contained the common cold virus. Researchers continued to monitor the participants for an additional week and took mucous samples to determine when the virus set in.
After adjusting for lifestyle and other factors noted in questionnaires, the researchers found those who slept less than six hours each night were over four times more likely to develop the cold, compared with participants who slept for more than seven hours each night. Participants who slept even less—five or fewer hours each night—were 4.5 times more likely to develop a cold. The researchers didn't observe a difference in cold susceptibility between participants who slept seven hours and those who slept eight or more a night.
"Sleep goes beyond all the other factors that were measured," Aric Prather, an assistant professor of psychiatry at the University of California, San Francisco, and lead author of the study, said in a press statement. "It didn't matter how old people were, their stress levels, their race, education or income. It didn't matter if they were a smoker. With all those things taken into account, statistically sleep still carried the day and was an overwhelmingly strong predictor for susceptibility to the cold virus."
Experts recommend that adults get at least seven to eight hours of sleep each night to stay physically and mentally healthy, though many people claim they can function on much less. According to the U.S. Centers for Disease Control and Prevention, 30 percent of adults sleep six or less hours of each night. This study and others like it suggest that nationwide sleep deprivation is a public health problem.
"Given that infectious illness (i.e., influenza and pneumonia) remains one of the top 10 leading causes of death in the United States, the current data suggest that a greater focus on sleep duration, as well as sleep health more broadly, is indicated," the researchers write in the study's conclusion.
