When you’re a kid, your parents set your bedtime. When you’re an adult, anything goes. No one can ground you anymore — you can stay up as late as you like, whenever you want! But should you? According to a recent study, the answer is no. Irregular sleep might be bad for your health.
The Science of Sleep
Led by Duke University researchers and published in Scientific Reports in September, the study focused on sleep regularity, or “sleep hygiene” — a relatively new frontier. Previous sleep research has looked more at how deeply people sleep and how long they’re asleep each night. Here, though, researchers took a different tack, examing long-term sleep patterns across almost 2,000 adults aged 54 to 93.
Subjects wore digital wrist devices that tracked the exact times they went to bed and got up each day — even a ten-minute deviation from routine was perceptible. Researchers also asked participants to keep track of their sleepiness during the day and used various biodata measures to monitor their cardiovascular and mental health.
They found that people with irregular bedtimes and wake times weighed more, had higher blood pressure and blood sugar, and were more likely to suffer from depression. Irregular sleeping was linked with negative future outcomes, too, including a higher risk for heart attacks and strokes in the next 10 years.
An unpredictable bedtime also correlated with sleepiness during the day — unsurprisingly — and a more sedentary lifestyle. It’s unclear which direction causation flows here. Participants might have been sedentary because they were tired, or vice versa, since exercise is a natural sleep aid.
The researchers also looked at a variety of sleep metrics beyond regularity, too: the quality of participants’ sleep, how long they slept, and their preferred bedtime. Were they night owls, or early-to-bed, early-to-rise types? But none of those had the predictive power of sleep regularity. A regular bedtime is that powerful.
Can a Bedtime Make You Healthy?
A consistent bedtime and wake-up time — yes, even on weekends — certainly correlates with better metabolic and cardiac health, at least in older people. (The study’s youngest participants were 54, so it remains to be seen if 20-somethings have to ditch the club when their designated bedtime rolls around.)
Correlation isn’t causation, though, and future research still has to isolate the causes at work here. Irregular sleeping could, for instance, just be a symptom of the real health issue: shift work, for example, which can be stressful and physically arduous (and often doesn’t come with health insurance).
Then again, the real health issue could also be a sedentary lifestyle or increased calorie intake. When a person’s circadian rhythms get disrupted, they tend to eat more and metabolize what they eat more slowly, especially if it’s sugary.
Though we don’t exactly know why irregular sleep links with negative health outcomes, this particular study’s findings can still help doctors target heart disease and diabetes prevention efforts. In the U.S., both diseases are leading causes of death, the study’s lead author noted. They’re costly to treat, too; the price of insulin, one treatment for diabetes, has more than tripled from 2002 to 2013.