A Number You Won’t Forget: 48 Percent

You’ve been told to aim for 7 to 9 hours of sleep per night. And you might even be aware of the dangers of sleeping fewer than 6 hours per night. But it’s not just about how long you sleep, but also when you shut down for the night.

A new study suggests that sticking to a consistent sleep schedule could be the key to a longer life. Scientists reviewed approximately 10 million hours of sleep-tracking data from more than 60,000 adults over 8 years to analyze the relationship between sleep schedules and longevity.

To no one’s surprise, people who got more sleep tended to live longer. But the data suggests that sleep regularity — or how consistent people are with their bedtime and wake-up schedules — was even more predictive of mortality risk. Participants with highly irregular sleep schedules (those whose sleep and wake times varied by more than 90 minutes across a week) had up to a 48 percent higher risk of mortality compared to those with consistent schedules.

It’s likely because all risk factors increased with irregular sleep schedules. Regular sleeping patterns were associated with a 16 to 39 percent lower risk of cancer mortality and a 22 to 57 percent lower risk of cardiometabolic mortality.

Irregular sleep disrupts your body’s circadian rhythm, the internal clock that regulates everything from hormone production to digestion. When your sleep schedule is unpredictable, upsetting your circadian rhythm can:

• Increase inflammation.

• Impair metabolic health, leading to conditions like diabetes and heart disease.

• Reduce immune system efficiency, making it harder for your body to fight off illness.

In other words, your body craves consistency. An erratic sleep schedule can wreak havoc on your body’s ability to maintain equilibrium, even if you’re technically “getting enough sleep.”

While you won’t be perfect every night, the data suggest going to bed within the same 1-hour window each night, weekends included. A regular sleep schedule could do more than help you feel rested; it might just add years to your life.