I can’t sleep and I hateSQUIRREL

It doesn’t matter whether you consider yourself an early bird, a night owl, or whatever temporal human-avian hybrid in between, you need sleep. Even if you love the night so much that you got a bunch of songs about it, whatever – you’re sleeping in the next day because a lack of sleep isn’t actually nice, and there are no songs that paint a lack of sleep in any good way. Well, maybe one

I digress (and if you’re familiar with this blog, thank you, and you should be used to digressions like that by now). See, we all work under circadian rhythms, the day-night cycle that regulates our body’s systems, particularly our hormones. Those are important as these are body signals that keep us stable, such as through concentration, mood, metabolism, and so forth. The key here isn’t so much when your day-night cycles kick in, but how consistent they are. According to the literature review carried out by the authors of this week’s OPEN ACCESS Featured Article, disruptions to one’s circadian rhythms (read: irregular sleep cycles) are associated to a lot of what we might call Very Bad Things, such as “cardiovascular disease, obesity, diabetes and some cancers” as well as “increased risk for major depressive disorder (MDD) and bipolar disorder (BD).” Spare a thought for people whose jobs require them to be on-call – nurses, police, firefighters, and the like – and how taxing being on-call is on their bodies and their minds, even if they don’t thankfully have to do it all the time.

640px-flickr_-_official_u-s-_navy_imagery_-_a_nurse_examines_a_newborn_baby
Flickr/Public Domain (Author: United States Navy, 2012)

You have stories about some of the dumbest things you’ve ever done on lack of sleep, we all do, but anecdotes do not a research paper make. After all, the robustness of observations in science requires a lot of replication. But what are you gonna do – interview 50,000 people? You’d never finish your research, and no one in their right mind is going to fund a study that large for that long, and you can’t count on everyone in the grant committee as sleep-deprived in just the right way; they may show up to the grant meeting with mismatched socks and missing trousers, but can still turn you down. Welp, the next best and quite good thing is biostatistics, or biology for people unafraid of very large numbers, keen on finding patterns, and making Microsoft Excel all but dance. They could come up with a question, find some patterns of their own, then cross-check it with a large storehouse of data, such as the UK Biobank. That’s what Ferguson et al. did to answer their question: are disrupted sleep cycles related to psychiatric disorders, such as anxiety, mood disorders, attention-deficit hyperactivity disorders, and so forth?

The researchers went through several types data from tens of thousands of people, one of which was data from wrist-worn accelerometers, often used in studies of physical activity. This was used to determine their resting-active cycles, and you would expect that the ‘rest’ part of the cycle is where there’s less activity showing up on the accelerometer, tossing and turning in your sleep notwithstanding. This was the main measure of the study, which the authors called the ‘relative amplitude,’ or RA, and defined as “a measure of the disrupted rest-activity rhythm.” A low measure of this implies more disruption; I’m not going to dive into the math much further since 1) I don’t have access to the prior study in which they did it and 2) I’m actually running on not much sleep because of too many cookies the night before…

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Public Domain (Author: Bosmin Kang, 2010)

Anyway, the authors also retrieved genetic data for that large number of people (they don’t need to do the genetic sampling anymore – you can save genetic data and retrieve it later) as well as results for several psychiatric questionnaires. With a sample that large, any patterns that they find could go far in answering their question.

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Public Domain (Author: Gerd Altmann, 2016)

So what did the authors find? The good news is that there weren’t significant genetic correlations between low RA scores and the psychological disorders that they examined, which means that one can’t strongly conclude that highly-disrupted cycles are related to ADHD, anxiety, mood instability, schizophrenia, and so forth (read the OPEN ACCESS Featured Article if you want to look into which disorders they tested for) when looking at genes related to inconsistent sleep cycles. However, disrupted cycles on their own are still related to some of the disorders they examined, such as mood instability, major despressive disorder, and neuroticism. This is not to say that disrupted sleep cycles cause these Very Bad Things, but they do have a lot of overlap.

A good night’s sleep ought to do you well, regardless of when you get it. Late, sleepless nights might be romanticized in stories of love, heroics, and more than a few motivational speeches, but you try being productive when your brain is six kinds ofSQUIRREL-

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Public Domain (Author: PublicDomainPictures, 2013)

And how good would your performance be then?

Thoughts? Comments? Embarrassing lack-of-sleep stories? Let me know in the space below, throw a like if you liked it, and you don’t need to be a WordPress member to do it! If you’re not doing so already, please follow (if you’re into scientific research with snarky commentary from an overly-caffeinated blogger-scientist who somehow gets enough sleep) and thanks again for stopping by.

Featured Article: Ferguson A, Lyall LM, Ward J, Strawbridge RJ, Cullen B, Graham N, Niedzwiedz CL, Johnston KJA, MacKay D, Biello SM, Pell JP, Cavanagh J, McIntosh AM, Doherty A, Bailey MES, Lyall DM, Wyse CA, Smith DJ. (2018). Genome-Wide Association Study of Circadian Rhythmicity in 71,500 UK Biobank Participants and Polygenic Association with Mood Instability. EBioMedicine. Article in Press. DOI: 10.1016/j.ebiom.2018.08.004.

Featured Image: Public Domain (Author: Ryan McGuire, 2015)

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