People who struggle with insomnia are often advised to go to bed and get up at the same time each day, as one of the “sleep hygiene” measures that may promote better slumber. But even if you’re a champion sleeper, two studies published earlier this year suggest another good reason to aim for a stable bedtime: your heart health.
In a study in the Journal of the American College of Cardiology, researchers examined data from 1,992 older adults, all initially free of cardiovascular disease. Sleep was tracked for a week at the start of the study. Those with the most variation in their bedtimes or in the amount they slept were more likely to have a cardiovascular event or die from cardiovascular disease in the next five years than those who went to bed at roughly the same time each night and slept roughly the same number of hours. The findings held up regardless of how long the person actually slept. The researchers adjusted for participants’ cardiovascular risk factors and self-reported sleep quality. Their conclusion: “Irregular sleep duration and timing may be novel risk factors for cardiovascular disease.”
The second study, in NPJ Digital Medicine, included 557 young adults. The researchers used Fitbits to track the participants’ sleep behavior over four years, logging a total of 255,736 sleep sessions. The individuals’ resting heart rates were recorded along with their sleep and wake times. Going to bed even 30 minutes later than one’s usual bedtime was associated with an increase in resting heart rate that persisted through the sleep session and into the next evening. (Usual bedtime was defined as the hour surrounding the individual’s average bedtime over all the nights of monitoring.) A higher resting heart rate has been linked to a greater risk of heart disease and premature death. The greater the deviation in bedtimes, the greater the heart rate increase.
Interestingly, going to bed an hour or more before the usual bedtime also raised resting heart rate, but it returned to normal faster. As in the other study, the effect of inconsistent bedtimes held up even if the person got a healthy amount of sleep (seven to nine hours) on a given night. The findings “stress the importance of maintaining proper sleep habits, beyond sleep duration, as high variability in bedtimes may be detrimental to one’s cardiovascular health,” the authors wrote.
Our advice: While more research is needed to determine how inconsistent sleep times affect the heart, it’s reasonable to try to head to bed around the same time each night and avoid sleeping radically different amounts from day to day. It can’t hurt, and it might help your sleep, your heart, or both.
This article first appeared in the UC Berkeley Wellness Letter.
Also see Are You Sleep Smart?