More in a continuing series about one of my favorite topics, something we all do every day, and spend roughly a third of our lives doing…sleep!

Since we are in the middle of the common cold season, this post will be particularly relevant.

It turns out, grandma was right. Getting good sleep really does prevent colds. This supports a favorite belief of mine—that I don’t believe in the germ theory of illness.  Read on and you will see why I liked the referenced article.

Researchers at a variety of universities collaborated and did a clever study looking at sleep and its effects on susceptibility to the common cold. First they had their 153 subjects, healthy men and women between 21 and 55, report their sleep duration and efficiency for 2 weeks. (Efficiency is what percent of the time you are actually sleeping while in bed.) Next, these diabolical researchers sprayed cold virus up the noses of all the subjects (in quarantine), and watched what happened over the next 5 days.

The results were very interesting. Those subjects who slept less than 7 hours were almost 3 times more likely to develop a cold than those who slept 8 hours or more. In addition, those whose sleep was less than 92% efficient were 5.5 times more likely to develop a cold than those with 98% or more sleep efficiency. Interestingly, how rested subjects reported feeling after sleep was not associated with colds.  The lead author of the study concluded, “The longer you sleep, the better off you are, the less susceptible you are to colds.”

Now I promised that I would report evidence that this study bolsters my theory that germs don’t really matter that much. Remember the researchers sprayed virus up everyone’s noses. After five days, the virus had infected 135 of 153 people, or 88% of the people, but only 54 people (35%) got sick. What this suggests is that even among the people who were infected with cold virus, 60% stayed healthy, while 40% got sick. And the ones who got sick were much more likely to have reported less and lower quality sleep in the two weeks before infection. 

This is very relevant for everyday life, since much of the time we can’t really avoid exposure to common germs like colds and flu. If good sleep protects us even when infected with such germs, then it may be the key to staying healthy.

What is truly fascinating about this study is the precise immune regulation showed by those who got infected, but stayed healthy. To understand this let me digress for a moment with a short primer on the common cold. Most people think cold symptoms are caused by cold virus. This is wrong. Actually, cold symptoms are caused by our bodies’ immune reaction to the cold virus. Our bodies produce germ fighting proteins called cytokines, and when our bodies make too much, we get the congestion and runny nose symptoms. If our bodies make just the right amounts of cytokines, we fight the virus without feeling sick.

So getting 8 or more hours of sleep a night may allow your body to fine tune an immune response, and make just the perfect amount of germ fighting proteins.

Another interesting finding is the relationship of sleep efficiency and illness. Sleep efficiency was an even more powerful predictor of getting sick than total sleep. (Of course, this might reflect an overall difference in sleep quality. Those who sleep deeply may tune up their immune systems better, and they are likely to spend most of their time in bed asleep.)

But assuming that increasing sleep efficiency is useful, then those people who take a long time to fall asleep, and who sleep fitfully may benefit from spending less time in bed, and working on sleeping more of the time they are in bed. On the other hand, those who fall asleep as soon as their head hits the pillow, and who are sleep like logs, would probably benefit from spending a little more time in bed, since they are not getting enough sleep.

So there you have it. Sleep 8 hours or more, try to sleep well, and you can lower your odds of getting a cold greatly. Even if you are exposed to the virus, if you have good sleep quality, you probably won’t get sick. So much for the simple germ theory! I suspect that this applies to all infectious diseases. So getting good quality and quantity in sleep may be one of the most important health behaviors for staying well.

It’s late, and I’m off to bed now…..zzzzzzzzzzzzzzz.

Copyright © 2009 The Psychology Lounge/TPL Productions/Andrew Gottlieb

It’s been a while since I wrote, and some of that is that I’ve been trying to get to bed earlier, and get a more consistent 8 hours of sleep. Since I last wrote, I saw an interesting factoid from an interview with Daniel Kripke, who is the co-director of the Scripps Clinic Sleep Center in La Jolla, California. In this interview, he talked about research he did on more than 1 million Americans that correlated sleep and mortality. There were some surprising findings, which have been corroborated by similar studies in other countries.

The results showed that those who slept between 6.5 and 7.5 hours a night lived the longest. And that those who slept more than 8 hours a night or less than 6.5 hours a night don’t live as long. This is interesting in that most previous writing I have seen suggests that sleeping more is good for you, but these data don’t support that.

Another good point he made was that when people try to get too much sleep, because they think the normal amount is 8 or 9 hours, they may unintentionally develop insomnia. Staying in bed longer than you can sleep will result in wakefulness, and anxiety about not being able to sleep. So for those of you who only can sleep 6.5 or 7 hours, just get up, it won’t hurt your health. In fact, restricting the time in bed is a more effective treatment for insomnia than sleeping pills, according to Kripke.

What we don’t know is which direction the causality runs in this association. Does the amount of sleep you get create your health status, or is it a reflection of underlying health? Do sicker people sleep too little or too much? Or does sleeping too little or too much make you sicker? No one knows for now, so I wouldn’t necessarily rush to change your sleep habits based on this study. But if you are sleeping in the 6.5 to 7.5 hour range, you can relax and not worry about it (especially late at night!)

Now I’ve got to stay up a little longer, so I don’t get too much sleep tonight…

Copyright © 2008 The Psychology Lounge/TPL Productions