The Sleep Habit That Could Mean You're More Likely To Die Early

Sleep seems like one of those things that's impossible to get right. It's supposed to be the time when we get much needed rest and our brains restore themselves so that we can arise the following day fresh as a daisy. But when you start looking into it, sleep is fraught with all sorts of problems, mysteries, and counter-intuitive facts. Did you know, for instance, that too much sleep may decrease your life span? Or that getting too little sleep too often is one of several habits that could also mean you die early? How about the fact that the findings of one study suggest that nightmares aren't just deeply upsetting experiences, but could also predict cognitive decline later in life?

It really is striking how complicated sleep is when you think about it, and now there's another sleep habit we've all got to worry about which could also lead to a premature death. A recent study suggests that rather than the length of sleep we get, the regularity of our rest is the most important in terms of our mortality risk. That means that alongside worrying about whether we get too much or too little sleep, we've got to start worrying about how often we're sleeping and when we got to bed, too, making an already complicated topic even more convoluted.

In a study entitled "Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study," researchers looked at the day-to-day consistency of sleep–wake timing and determined that this can be a stronger predictor for certain negative health effects than whether individuals get too much or too little sleep. In the 2023 study, published in the journal Sleep, scientists looked at health data from 60,977 participants, comprising around 10 million hours of recorded sleep, and calculated what they termed "sleep regularity index" scores. They then recorded participants' death rates over an average of 6.3 years.

Irregular sleep was associated with a greater risk of all-cause death as well as death from cancer and cardiometabolic causes. The results showed that those who had more sleep regularity had a 20% to 48% lower risk of all-cause mortality and a 16% to 39% lower risk of dying from cancer than those with the lowest scores for sleep regularity. They were also shown to have a 22% to 57% lower risk of cardiometabolic death. The study overall suggests that sleep regularity — falling asleep and waking up at the same time consistently — was a stronger predictor of all-cause mortality than sleep duration. Based on these findings, sleep regularity appears to be a way that anyone can improve their overall health.

Does that mean we don't need to worry about how long we're sleeping? Not at all. The study still showed that those who slept for fewer than six hours or more than nine each night were actually at a higher risk of mortality. It's just that sleep regularity was shown to be a more reliable predictor of health issues.

The 2023 study wasn't the first time that the importance of sleep regularity had been highlighted, or even the first time regularity was discussed as a predictor of health issues. It followed a 2023 consensus statement from the National Sleep Foundation which was published in the journal Sleep Health. The statement explains the consensus views of a panel of sleep experts on sleep timing and variability. Following a systematic review of the literature, the panel urged that maintaining a consistent sleep schedule is important for health, safety, and performance and advised those who struggle to keep to a consistent and regular sleep schedule to aim for "catch-up sleep" when they can.

Prior to that, a 2021 study published in Frontiers in Neuroscience showed that irregular sleeping and waking patterns were associated with a reduced quality of life for those recovering from cancer treatment. Those with more regular sleep schedules had better overall physical functioning and fewer cancer-related symptoms, leading the researchers to conclude that improving sleep regularity may be a simple and effective way to improve the quality of life for cancer patients. Furthermore, a 2018 study published in Scientific Reports used the sleep regularity index in relation to a group of older adults and found that irregular sleep was linked with cardiometabolic health issues. Those with higher levels of sleep irregularity were, for example, correlated with a higher 10-year risk of cardiovascular disease as well as obesity, hypertension, fasting glucose, and diabetes.

The 2023 study was, however, the first time a very large group of participants was evaluated for sleep regularity using objective data, and therefore represents an even more convincing argument for sleep regularity being hugely important for your health later in life.