Sleep cycles and the myth of “broken sleep”

Sleep quality is important. A poor night’s sleep can mean an uphill battle for the rest of the day as you deal with irritating people, struggle to concentrate, and try your best to keep a lid on your frustration. You know when you’ve had a bad night of sleep - when you’ve woken up multiple times throughout the night and when that solid, unbroken stretch of sleep has proved just a little too elusive.

Except…it’s not quite that simple. Sleep quality IS important, no doubt about it, but our perception of sleep quality is also extremely important, and our perception doesn’t always match up with the reality. In studies in which objective sleep measures (such as polysomnography or actigraphy) are collected alongside subjective sleep measures (such as sleep diaries or questionnaires), our perceptions of how well we slept in a given night have a significant effect on our emotional state the following day. When we perceive that we’ve had a bad night of sleep, we tend be less satisfied than on days following a perceived good night of sleep, even if the amount of sleep on both nights was the same. The reason why sleep researchers will often use complex and expensive equipment and techniques to assess sleep quality is because, unfortunately, we’re not able to estimate our sleep quantity or quality as accurately as we think we can. Many of us will tend to think of a night with several awakenings as a bad night, and a night with an unbroken block of sleep as a good night. Thanks to our sleep cycles, however, those good nights are maybe a little more mythical than we think.

Sleep cycles are periods of around 70-120 minutes in which our brains move between different stages of sleep, from light sleep to deep sleep and back again. Most people will experience 4-6 sleep cycles over the course of the night, and as the night progresses, the deep sleep gets a little lighter, and the light sleep gets a little longer. It’s not uncommon to wake up during the lighter stages of sleep, especially as we approach morning. As a result, many people will wake 3-5 times during the night. Some of those awakenings you might get up and get a drink or use the bathroom, but many of them you won’t remember at all - you might roll over, find a new position, fall back asleep 30 seconds, and wake up in the morning without even knowing they even occurred. That includes the “good nights” - even on those good nights, you have experienced regular nighttime awakenings, you just likely haven’t remembered them.

Another factor that contributes to confusion around our sleep quality is that stage 1 sleep, the lightest stage of sleep, is often not strikingly different from being awake with our eyes closed. It’s a transitional sort of sleep, where we drift hazily from wakefulness into deeper sleep. Sometimes, another person can have a conversation with you while you’re in stage one sleep and you might respond quite comprehensibly - but have absolutely no memory of anything you’ve said! However, if you’re drifting in and out of stage 1 sleep, and then you fall into deeper sleep and then come back out, it can feel like you haven’t slept at all. You might look over at the clock and discover that an hour and a half has passed since you last looked at the time, and be filled with frustration that you’ve been trying to sleep for so long without any success - even if you’ve been in deep sleep for most of that time.

When we awaken in the morning and think back to the night we’ve had, it’s worth remembering that nighttime awakenings are a completely normal part of sleep, and don’t necessarily mean that we’ve not gotten enough sleep. An unbroken 8 hour block of sleep is simply not a realistic goal for anyone to aim for, and striving for it comes at a cost - if we perceive our sleep as inadequate, we’ll feel like it’s inadequate. It’s also worth noting that our cognitive capabilities, our memory, and our problem solving - none of these things are at their best at 2AM, and it’s understandably difficult to think logically about these matters in the moment. The very nature of light sleep means that it’s sometimes going to be hard to determine if you’ve been asleep or awake. One helpful tip is that if you think you’ve been awake for an hour, but it’a real struggle to determine what you’ve actually been thinking about for that hour, you might have drifted into sleep for some of that time.

However, all of this comes with a caveat - while nighttime awakenings are normal, the length of time we spend awake during the night can be cause for concern. A couple of brief awakenings during the night won’t do any harm, but 3-4 awakenings of half an hour each will start to take a significant toll on your total sleep time. If you’re experiencing regular extended nighttime awakenings, it may be time to consult with a health professional, as such awakenings may be the result of sleep maintenance insomnia or another sleep condition. The vast majority of sleep conditions are treatable with effective, evidence-based interventions. If you’re concerned about your sleep, consult with a qualified health professional for additional clarity and support. After all, if you’re going to do something for a third of your life, you might as well enjoy it.