You're 3 Times More Likely to Get Sick If You Do This at Night, Study Says

Your immune system will suffer if your nighttime routine is not up to par.

The common cold can be caused by over 200 types of viruses, but it's most often the result of rhinovirus, experts say. Once exposed to a cold virus, your body relies on its natural ability to fight it off, and certain key factors can influence just how well your immune system does the job. In particular, studies have shown that how much sleep you get can greatly help or hinder your immune function. Clocking the right amount of rest gives you a fighting chance against colds, while skimping on sleep can leave your body susceptible to sickness. Read on to learn how much sleep makes you three times more likely to develop cold symptoms, and to find out why good "sleep efficiency" is just as important.

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Getting less than 7 hours of sleep makes you 3 times more likely to get a cold.

sick woman coughing Neds to get lungs checked

According to a 2009 study published in JAMA Internal Network, your chances of developing a cold triple if you regularly clock under seven hours of sleep per night. After controlling for "pre-challenge virus-specific antibody titers, demographics, season of the year, body mass, socioeconomic status, psychological variables, or health practices," the team found that "participants with less than seven hours of sleep were 2.94 times more likely to develop a cold [when exposed to rhinovirus] than those with eight hours or more of sleep," wrote the researchers.

The team says their findings can be explained with the help of past research, which has linked the poor sleep to lower immune function, due to "reduced natural killer cell activity, suppressed interleukin-2 production, and increased levels of circulating pro-inflammatory cytokines."

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Sleep efficiency also affects your odds of getting a cold.

Man with a cold on the couch blowing his nose

Sleep efficiency is the percentage of time spent asleep while in bed, and it's another way to measure one's quantity and quality of sleep. Experts from the Hypersomnia Foundation write that one's sleep efficiency "is calculated by dividing the amount of time spent asleep (in minutes) by the total amount of time in bed (in minutes). A normal sleep efficiency is considered to be 85 percent or higher," they note.

As it turns out, sleep efficiency is even more important than overall hours spent sleeping, say the JAMA researchers. "Participants with less than 92 percent efficiency were 5.50 times more likely to develop a cold than those with 98 percent or more efficiency," the team wrote. "Poorer sleep efficiency and shorter sleep duration in the weeks preceding exposure to a rhinovirus were associated with lower resistance to illness," they add.

Getting less than 7 hours of sleep has other health consequences.

Man talking to doctor about being screened for diabetes

According to the Centers for Disease Control and Prevention (CDC), getting less than seven hours of sleep per night is associated with higher risk of several chronic illnesses. In fact, the health authority says that those who report short sleep duration (defined as under seven hours) are more likely to experience heart attack, heart disease, stroke, asthma, chronic obstructive pulmonary disease (COPD), cancer, arthritis, depression, chronic kidney disease, and diabetes when compared to individuals who report sufficient sleep (defined as seven hours or more per night).

Ultimately, the heightened health risks associated with frequent poor sleep can have serious implications. A 2010 study in the journal Sleep, which reviewed data from 1,382,999 individuals across 16 studies, determined that those who slept for less than seven hours per night suffered "an increased risk of death from all causes."

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Sleep deprivation is more common than you might think.

older man with gray hair awake in bed at night
Shutterstock / Monkey Business Images

While the side effects of poor sleep are well documented, the CDC says that 35 percent of the American population still fails to get adequate rest, clocking under seven hours of sleep per night.

"The percentage [of people getting insufficient sleep] varies considerably by state, from less than 30 percent in Colorado, South Dakota, and Minnesota to more than 40 percent in Kentucky and Hawaii," explains the health authority. "The highest percentages [of people with inadequate sleep] were in the southeastern United States and in states along the Appalachian Mountains. The lowest percentages were in the Great Plains states." Age also appears to play a role, says the CDC: those over 65 are less likely to report insufficient sleep than those under 65.

According to the Sleep Foundation, the symptoms of insufficient sleep include slowed thinking, reduced attention span, poor memory, low energy, poor or risky decision-making, mood changes, and more. Speak with your doctor now if you notice these signs of sleep deprivation to determine whether it's affecting your health, and how to get a better night's rest.

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Lauren Gray
Lauren Gray is a New York-based writer, editor, and consultant. Read more
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