The evidence is now solid: short sleepers are far more susceptible to colds than average sleepers. Results of a study published this month in the journal Sleep show that people who sleep 6 hours or less are over 4 times as likely to catch a cold as people who get over 7 hours a night.
This may come as no surprise. If you’ve got insomnia, or if you’re naturally a short sleeper, you’ve probably had quite a few colds and suspected it had something to do with your sleep. You’re right: sleep shores up the immune system, and getting too little leaves you vulnerable to getting sick.
Here’s more about it and steps you can take to dodge the bullet this year as cold and flu season begins.
Importance of This Study
Other studies have shown that response to the flu vaccine is impaired in people whose sleep is partially restricted, and that short and inefficient sleep—as assessed by study participants themselves—confers lower resistance to illness.
But in the new study of 164 healthy volunteers, it was participants’ natural sleep behavior that was assessed (rather than their sleep being arbitrarily restricted). Also, their sleep was measured objectively. In addition to filling out sleep diaries for a week, at night they wore wristwatch-type devices designed to monitor sleep duration and continuity.
Participants also underwent 2 months of health screenings during which researchers collected information about their temperament, lifestyle, and habits. Following sleep assessment, participants were sequestered and given nasal drops containing a cold virus. Researchers then collected mucus samples daily for 5 days to monitor for cold development.
Perhaps more surprising than the main result was the fact that no other variable taken into account (smoking and alcohol consumption, for example) was as predictive of the likelihood of catching a cold as sleep duration.
“It didn’t matter how old people were, their stress levels, their race, education or income,” said Aric Prather, lead author of the study, quoted in ScienceDaily. “It didn’t matter if they were a smoker. With all those things taken into account, statistically sleep still carried the day.”
When Getting More Sleep Isn’t Easy
The take-away here is something you’ve heard before: if you want to stay healthy, get more sleep. I’m all in favor of that—when it’s possible. I’ve spent quite a bit of time studying and writing about how to get more sleep. Take a look at some of my suggestions by exploring the topic cloud to the right of this blog. (My book, The Savvy Insomniac, contains still more suggestions).
But for all the ways sleep can be improved by adopting changes in habits, mindset, and lifestyle (and, some will argue, with medication), some aspects of sleep are less amenable to change than others. Sleep length and sleep quality, for example, are partially determined by genetic factors. Twin studies suggest the heritability of sleep length and sleep quality is about 40 to 50 percent: similar to the heritability of general intelligence. No matter how much you’d like to be an 8-hour sleeper, it may not be in the cards.
The advice to get more sleep could be useful for people who willingly short themselves on sleep. It might translate into a resolve to go to bed earlier, in turn helping people stay healthy.
But getting more sleep is not such a straightforward matter for short sleepers or insomniacs, who can’t get the amount or quality of sleep we want even when given the opportunity. Going to bed earlier most likely will not do the trick. That usually tends to make insomnia worse.
Neither can we know when situations will arise that cause stress and interfere with sleep. For all we practice good sleep hygiene, it may be impossible to get anything approaching 7 hours’ sleep a night.
Tips for Avoiding Colds and Flu
We can be otherwise proactive in shoring up our immune systems to avoid colds and flu:
- Get a flu shot. Flu shots are available at pharmacies and doctors’ offices now.
- Get moderate to vigorous exercise at least 5 days a week. Results of two well-controlled studies showed that healthy young and older women who walked briskly 35 to 45 minutes a day 5 days a week for 12 to 15 weeks experienced about half the days with cold symptoms as women in the sedentary control groups. Regular exercise appears to boost the immune system in ways that reduce susceptibility to colds over the long term.
- Eat a balanced diet, minimizing sugar and simple carbohydrates. If you’re trying to lose weight, don’t restrict your caloric intake too drastically. Immune function is suppressed during times of very low caloric intake and quick weight loss. Gradual weight loss is more congenial to a healthy immune system.
- Reduce your exposure to germs. Viruses are mostly spread through the air (via coughing and sneezing) and then inhaled. Touching surfaces that harbor viruses—public computers and doorknobs, for instance—and then absentmindedly touching your face can also result in infection. Wash your hands with soap and water frequently and at length, and make liberal use of hand sanitizer. When a family member is sick at home, avoid sharing towels, and wipe down telephones and faucets often.