Inconsistent Sleep Schedule Tied To Nearly 200 Diseases, Confirming Your Suspicions

For all of our adult lives, we’ve read study after study telling us over and over again “No. Really. You need to get a good night’s sleep. It’s really important for your health.” And the new study we’re going to talk about today is no exception. but it does offer a few interesting twists. Researchers from Peking University and Army Medical University drew from data from nearly 88,500 adults from the UK Biobank (UKB) to discover that poor sleep habits — though not necessarily the ones you expect — were tied to significantly higher risks of dozens of diseases and 172 overall. Ninety-two diseases had more than 20% of their risk attributed to poor sleep. So… great news for those of us already tortured by tossing and turning every night.

Unlike most sleep studies, which rely on self-reported data and mainly look at sleep duration, this study was based on folks wearing accelerometers and measured multiple dimensions of sleep. Scientists studied nocturnal sleep duration and onset timing, sleep rhythm/consistency, and (c) sleep fragmentation. They found that while sleep duration wasn’t particularly tied to diseases (great news for those of us eking out five to six hours a night), having a disrupted circadian rhythm (a.k.a. having inconsistent bedtimes) was tied to higher risks for Parkinson’s disease, Type 2 diabetes, kidney failure, COPD, liver cirrhosis, and gangrene (that one threw me for a loop, NGL).

A mediation analysis showed that inflammation — caused by factors like leukocytes, eosinophils, and C-reactive — contributed to several of these chronic conditions.

“Sleep is a fundamental life requirement and is critical for multiple biological functions, including brain waste clearance, inflammatory cytokine release, and nutrient metabolism,” the study, which was published in the journal Health Data Science, reads. “With the widespread use of artificial lighting and the ‘24/7’ lifestyle, the human sleep experience has significantly changed from that of our pre-industrial revolution ancestors … Whether the human physiological systems that evolved over deep history could adapt to the current sleep pattern is a question that deserves specific attention for its potential impact on human health.”

It wasn’t all bad news, though, particularly for those among us who “indulge” in lengthy sleep. Contrary to previous studies, adults who slept more than nine hours a night were not observed to have any ill effects. Now, do I know anyone getting more than nine hours of sleep? I don’t think so, but good for them nonetheless.

Before you panic, there are limitations to this study.

For one, the subjects are not representative of the general population; under 6% of the invited participants attended the baseline (used to establish a baseline of participant health) and those were mainly middle-aged or elderly and therefore more susceptible to certain diseases, including those found associated with poor sleep. As such, researchers caution against full-throated generalization of these results.

For another, none of these diseases were conclusively and exclusively tied to sleep. Subjects with COPD, for example, often had a covariant of preexisting asthma, which is often tied to an overproduction of eosinophils (a type of white blood cell). So it’s not like inconsistent bedtimes gives you COPD or gangrene (I don’t know how that would work), but this is just saying it may contribute to it in some people.

Authors also admitted the possibility of reverse causation bias and some false positive mistakes, among other issues. Nevertheless, these preliminary results point to the reality that scientists need to take a more nuanced look at how we’re sleeping… and how, specifically, we can improve it.