What is Non 24-Hour Sleep Wake Disorder?

For your average person, their internal circadian rhythm (which controls when you wake up, how long you stay awake for, when you start to get tired, when you go to sleep, and how long you sleep for) is set to a 24 hour cycle, meaning you'll go to bed and wake up at about the same time every day. There may be some variance; you might stay up later and sleep in later on weekends for example, but for the most part you wake in the morning and sleep at night.

The cycle of people with N24 however is, well, non-24 hour. The combined time that people with N24 stay awake and sleep for adds up to either more or less than 24 hours (more commonly over 24 hours).

Let's imagine for example someone who has n24 with a 25 hour cycle. They wake up at 7 AM, go about their day for the next 16 hours, and go to bed at 11 PM. They sleep for 9 hours, adding up to a total of 25 hours.

Letting the schedule drift forward like this uninterrupted is called "free running"

(though N24 is rarely as consistent as this example; our cycles don't advance precisely the same amount every day, and its not at all uncommon for there to be sudden multi-hour jumps forward in your cycle, or for your cycle to remain at a fixed wake up and sleep time for a number of days before drifting again, and sometimes it will even move backwards by an hour or two. It's all kind of messy).

OK, so why not just not free run?

Trying to adhere to a 24 hour cycle for someone with n24 is just as difficult as trying to adhere to a non 24 hour cycle would be to someone without n24. Just going to bed an hour earlier or sleeping an hour less would not work for our hypothetical n24 sufferer; the body's sense of when it SHOULD be asleep will keep moving even if you do force yourself to sleep outside of it.

So it's like insomnia / narcolepsy / insert non circadian rhythm sleep disorder here?

Not really. While other sleep disorders effect the ability to fall asleep, how often and when you fall asleep, how long you stay asleep for, how rested you feel after sleeping etc., circadian rhythm disorders are disorders of the internal body clock rather than of the sleep itself. If I'm allowed to free run without interruptions, I can fall asleep easily, sleep a healthy 7 to 9 hours, and feel rested after.

Isn't N24 something only blind people suffer from?

If you've heard of N24 before this post, it may be from the fact that it effects around 50-70% of the totally blind. While it is a more common condition among the blind, it can develop in the sighted population as well (such as myself).

So what are the knock-on effects of this disorder?

Being out of sync with the sleep-wake cycle the majority of the population operate off of understandably causes some problems. Holding down employment is difficult for sufferers of N24. Most jobs will require you to clock in and out at a consistent time, and we are not able to force ourselves into these schedules without suffering massive sleep deprivation as a result.

I myself am unemployed and reliant on disability payments because of my N24.

N24 makes having a social / romantic life difficult too: you're often going to be out of sync with the schedules of the people around you, and it can be hard to predict exactly when you're going to be awake or asleep ahead of time for scheduling meetups or events. My circle of friends are all online across the world in different time zones because it's difficult to form friendships locally while free running.

Wow, that all sounds like it sucks, are there any cures?

Not any that work consistently for everyone. Some people with N24 are able to entrain themselves to a 24 hour schedule with light therapy and melatonin treatment. I've also heard of the method of microdosing melatonin a few hours before the target sleep time to try and simulate when the brain of people without N24 starts to release natural melatonin.