This story suggests that a good night’s sleep might be important for fending off the common cold. It features some useful information about the study that’s the basis for the story and includes valuable comments from an independent expert. But it could have done some things better — particularly with the language it uses to characterize the findings and its discussion of alternatives to getting more Zs for staying cold-free.
The problems begin with the headline: “Sleep fights colds, study finds.”
Well, maybe. “Because we didn’t actually manipulate someone’s sleep, we can’t know whether it was a causative effect,” lead author Aric Prather told HealthNewsReview.org in a telephone interview. “That’s Methodology 101.”
It’s important to acknowledge that reporters often have no control over their headlines — nevertheless, we think the issue of misleading headlines is important and needs to be addressed.
For more concerns about the presentation of the findings, see “Quality of Evidence” below.
The question of how much sleep is optimal is important and largely unanswered. We know that humans get different amounts of sleep at different points in their lives, so age is clearly related to this issue. But it remains unclear how much sleep optimizes health. Though the study described in this piece does not address this larger issue, it attempts to get at this by focusing on the risk of infection. Here the common cold was induced artificially in a controlled setting among healthy individuals. The study found that those who, at baseline, slept more, were less likely to develop an objectively defined cold after being inoculated with the cold virus. This appears to be a well-done study, but doesn’t really answer the key question: If I sleep more, will I get fewer colds? That important question requires a different study to answer. Moreover, this study was done in artificial conditions. The more practical question is, If I sleep more during the cold season, will I be less likely to get a cold? Again, not something that this study, well-performed though it was, is capable of answering.
The story makes no mention of costs, but there is no obvious commercial product involvement here, so we’ll rate it Not Applicable. Although in theory there may be a cost to more sleep — people often give up sleep for work or other activities.
The story cites as benefits the reduced risk of getting a cold among those who got at least six hours’ sleep. But this benefit is described in relative terms (e.g. “those who slept for five hours or less each night were 4.5 times more likely to catch the cold). We think absolute terms are more informative. From figure 1 in the study, we can see that about 17% of those w/ >7hrs of sleep got the cold vs. ~45% of those with <5 hrs.
The story cites the increased risk of getting a cold with not enough sleep — with the attendant sometimes debilitating symptoms that are all-too-familiar to many. But mainly the story is advocating for more sleep — and could there be risks to getting more sleep or trying to stay in bed for 8 hours if you’re only hardwired to sleep for 6 hours? That’s unclear, but the story could have clarified that although more sleep is associated with fewer colds, that doesn’t necessarily mean that increasing your amount of sleep will reduce the number of colds you get. Proving that would require a different study. We’ll give the benefit of the doubt here.
Questions about the evidence begin at the headline, cited above in the summary. Because the study isn’t capable of proving whether there was a cause-and-effect relationship between sleep time and colds, stating that sleep “fights” colds is inappropriate. This study doesn’t demonstrate that if one increases sleep time from 5 to 7 hours, that getting a cold is less likely. It shows an association between those factors, not that one leads to the other.
The questions continue with the lede, which tells the reader to try going to bed earlier rather than loading up on Vitamin C and zinc. But the implied promise that we’ll learn something about these two home remedies is never fulfilled. The story goes on to tell us nothing about Vitamin C or zinc, neither of which is mentioned in the study.
Finally, while we don’t necessarily think the story was required to explore the results in this much detail, it certainly would have been useful to point out that this study was carried out in a highly controlled setting. In real life, people aren’t just concerned with the number of laboratory defined colds they get — they also want to know whether changing sleep habits lead to fewer cold symptoms, less missed work, and reduced productivity. Imagine someone who gets 3 colds per year that sideline her for 5 days each (15 days total per year). Now that person increases her sleep by 2 hours a night (730 more hours per year, representing ~30 days). If that person gets one less cold per year (10 days total), is she better off? Those 5 days saved came at the cost of 30 days that could have been spent awake doing something!
The story makes no mention of the incidence or severity of the common cold. So in that respect, we can’t really give credit here for avoiding disease-mongering. We’ll rule in Not Applicable.
The story includes remarks from Dr. M. Safwan Badr, who was not involved with the study. He brings some useful perspective as far as what is new about the study.
The story did not provide any meaningful discussion of possible alternatives to reducing colds such as frequent hand-washing. As noted above, the benefit of more sleep = less colds comes at a cost of having less awake time to do things. Some people might be better off having more colds! That makes alternatives potentially important.
Of course, not everyone can find six or more hours in a day to sleep. But the study did not address this.
The story notes that “the study is unique because it used objective measures to show that poor sleep habits make people more vulnerable to a cold virus.”
The story did not rely overly on this news release.