5 Sleep Phenotypes, By Actual Science

You probably know people can be broadly divided into “early birds” and “night owls”:

Early Bird Or Night Owl? Genes vs Environment

…and then the term “hummingbird” gets used for a person who flits between the two.

That’s three animals so far. If you read a book we reviewed recently, specifically this one:

The Power of When – by Dr. Michael Breus

…then you may have used the guide within to self-diagnose your circadian rhythm type (chronotype) according to Dr. Breus’s system, which divides people into bears, lions, wolves, and dolphins.

That’s another four animals. If you have a FitBit, it can “diagnose” you with being those and/or a menagerie of others, such as giraffe, hedgehog, parrot, and tortoise:

How Fitbit Developed the Sleep Profile Experience (Part 2 – Sleep Animals)

Five million nights

A team of researchers recently took a step away from this veritable zoo of 11 different animals and counting, and used a sophisticated modelling system to create a spatial-temporal map of people’s sleep habits, and this map created five main “islands” that people’s sleep habits could settle on, or sometimes move from island to island.

Those “five million nights” by the way? It was actually 5,095,798 nights! You might notice that would take from the 2020s to the 15970s to complete, so this was rather a matter of monitoring 33,152 individuals between January and October of the same year. Between them, they got those 5,095,798 nights of sleep (or in some cases, nights of little or no sleep, but still, they were there for the nights).

The five main phenotypes that the researchers found were:

1. What we think of as “normal” sleep. In this phenotype, people get about eight hours of uninterrupted sleep for at least six days in a row.
2. As above for half the nights, but they only sleep for short periods of time in bouts of less than three hours the other half.
3. As per normal sleep, but with one interrupted night per week, consisting of a 5 hour sleep period and then broken sleep for a few more hours.
4. As per normal sleep generally, but with occasional nights in which long bouts of sleep are separated by a mid-sleep waking.
5. Sleeping for very short periods of time every night. This phenotype was the rarest the researchers found, and represents extremely disrupted sleep.

As you might suspect, phenotype 1 is healthier than phenotype 5. But that’s not hugely informational, as the correlation between getting good sleep and having good health is well-established. So, what did the study teach us?

❝We found that little changes in sleep quality helped us identify health risks. Those little changes wouldn’t show up on an average night, or on a questionnaire, so it really shows how wearables help us detect risks that would otherwise be missed.❞

~ Dr. Benjamin Smarr

More specifically,

❝We found that the little differences in how sleep disruptions occur can tell us a lot. Even if these instances are rare, their frequency is also telling. So it’s not just whether you sleep well or not – it’s the patterns of sleep over time where the key info hides❞

~ Dr. Edward Wang

…and, which gets to the absolute point,

❝If you imagine there’s a landscape of sleep types, then it’s less about where you tend to live on that landscape, and more about how often you leave that area❞

~ Dr. Varun Viswanath

In other words: if your sleep pattern is not ideal, that’s one thing and it’d probably be good to address it, by improving your sleep. However, if your sleep pattern changes phenotype without an obvious known reason why, this may be considered an alarm bell warning of something else that needs addressing, which may be an underlying illness or condition—meaning it can be worthwhile being a little extra vigilant when it comes to regular health screenings, in case something new has appeared.

Want to read more?

You can read the paper in full here:

Five million nights: temporal dynamics in human sleep phenotypes

Take care!