In the latest New Yorke r, an article by Jerome Groopman is about the emergence of even-more-antibiotic-resistant bacteria.
I asked him what we should do to combat these new superbugs. “Nobody has the answer right now,” he said. “The fact of the matter is that we have found all the easy targets” for drug development. He went on, “So the only other thing we can do is continue to work on antibiotic stewardship.”
All the easy targets, huh? Here’s an easy target that hasn’t been exploited: Why are colds more common in the winter? Many diseases are more common in the winter. I believe it’s because sleep is worse in the winter. While you are asleep is when your body does its best job of fighting off infection. When I vastly improved my sleep — by standing much more, and by getting more morning light — I vastly reduced the number of easy-to-notice colds that I got. I still got cold infections, I think, but they merely caused me to sleep more than usual for a few days.
Several years ago I noticed an introductory epidemiology course in the UC Berkeley School of Public Health was taught by someone I knew. I called him. “Is your course going to cover what makes our ability to fight off infection go up or down?” I asked. No, he said. That is the usual answer. The question of why colds are more common in the winter is not part of the traditional study of epidemiology.
The connections between sleep and fighting off infection are so strong I’m pretty sure I’m right about this (that colds are more common in the winter because sleep is worse). Why, then, haven’t sleep researchers looked into this? Strangely enough, they may not have thought of it; I haven’t come across this idea in any book about sleep I’ve read. (If you’ve seen it somewhere, please let me know!) Justifications of sleep research tend to revolve around car accidents, which are often caused by too little sleep.
More. My point is not that poorer sleep causes more colds in the winter; it’s that it’s an easy target. Suppose you think the colds/winter connection is caused by less Vitamin D in the winter. An experiment in which one group gets Vitamin D supplements in the winter and another group doesn’t is easy to do, given the great health implications.
I can’t think of any reason why sleep should be worse in winter; as far as I can tell, it ought to be better due to longer hours of darkness. As for the relative increase in colds during winter, several other factors come to mind: less sunlight means less vitamin D production and thus weaker immune systems; less sunlight also means lower microbicidal ultraviolet radiation; cold weather means people are indoors more and can more easily communicate pathogenic microbes to each other.
dennis, i thought it was odd too that sleep could be worse in the winter. i had an odd thought: if you sleep poorly in winter, you might be groggy and therefore not able to do much during the day, limiting your energy expenditure when you might need to conserve it. in the summer, if you sleep well, you have energy to make use of the long days. winter tends to be associated with depression, which manifests sometimes as low energy and poor sleep.
Demmet’s big book on sleep is full of interesting stuff.
For a long time now, I’ve noticed that I sleep much better in the winter when the ambient indoor temperature is cool (and I can snuggle up warm and toasty under the covers) than in the summer, especially when it’s hot. In warm weather especially it takes me longer to fall asleep, I feel less comfortable in bed, I wake up more frequently, have more bouts of insomnia, and wake up earlier than when the weather is cooler. I love summer but I always dread the uncomfortably warm sleepless nights.
I don’t buy the bad sleep in winter thing. Not true for me.
Besides, I thought it was the lack of vitamin D which caused colds and influenza in winter (unless you lived someplace sunny that is).
Dennis & John, I have seen at least one study showing that sleep is worse in the winter. There is a reference to it in that self-experimentation article. I believe sleep is worse in the winter because there is less morning light — that light increases the amplitude of a circadian oscillator that controls sleep is not exactly a revolutionary idea. But even if I’m wrong, something that has a big effect on rate of infection changes a lot from summer to winter. If it turns out to be Vitamin D, for example, that would be very helpful to know.
People cluster closer together, indoors, in the winter, so transmission is increased. Just a small difference in the number of people in proximate location to each other translates into huge exponential growth in infection.
I agree that inadequate sleep can be a contributing factor to getting a cold. That’s definitely been true in my case. Given time to catch up on sleep and some Zicam zinc lozenges I can fight off any cold.
As for why colds are more common in the winter, I read “somewhere on the internet” that this is due the fact that the in colder, less humid weather the mucus in your nasal passages dries up making it easier for the germs to get in.
My guess would be some combination of factors. I’d be interested to see data about when cold season starts in the northern areas versus southern areas.
This may be of interest: “Epidemic influenza and vitamin D”
https://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=469543
Just to raise more potential contributing factors, there is the stress from the holiday season to consider, plus all of the extra travel from Thanksgiving to Christmass/Hanuka (sp?), then New Years. This raises the question as to whether infectious illnesses like the common cold are more common in winter in ALL cultures or largely in western society?
Aaron: they are. Furthermore, they’re more common then in completely isolated communities (i.e. not brought in by outsiders). They’re more common where it’s always hot. They’re more common where it’s always cold. The only important variable is that in the southern hemisphere, the phase is reversed.
Evidently I wasn’t clear: colds are more common in winter everywhere, even in places that are always cold, and places that never really get cold, and places that get no visitors. You’re left trying to explain it by reference to light and to temperature changes vs. the summer baseline.
Evidently I wasn’t clear: colds are more common in winter everywhere, even in the Yukon, and in the tropics, and in places that get no visitors. You’re left trying to explain it by reference to light and to temperature changes vs. the summer baseline.
I suppose another possibility is that the body’s cold-fighting ability has an annual rhythm. Perhaps the systems that fight off infection need a respite after a period of intense activity. If the organism’s most important activities (reproduction, food-gathering) take place in summer, it may sense to schedule the down time for winter. The obvious alternative – maintaining a lower but constant level of robustness year round – might be suboptimal.
To complete my thought: In that case, looking for environmental cause of wintertime liability to infections would be a dead end.
On the other hand, it coudl be Vitamin D! (BTW, in light of the new studies on Vitamin D, doesn’t it strike you as scandalous that this reasearch wasn’t done decades ago? You’d think that correlations between all well-known nutrients and population health would be considered basic statistics, the public-health equivalent of the national census.)