It was reported Nov. 9, 2021, in the Washington Post.
What's the most important thing people should know about this study as it relates to their health?
Heart disease is the number one cause of death worldwide. Poor sleep has been shown to increase risk for heart disease. By making changes to sleep habits, people may be able to lower their risk for heart disease. This benefit could be greater for women than men.
What was this study seeking to determine? Has this been done before?
This study evaluated the association between the time a person goes to sleep, otherwise known as sleep timing, and development of heart disease. Previous studies have looked at other measurements of sleep, such as length of sleep or quality of sleep. But this was the first study focused on sleep timing. This study was unique because it used a wrist-worn device to detect the exact time the person went to sleep.
What were the results?
The study found that there is an increased risk for heart disease when people go to sleep before 10 p.m. or after 12 a.m. The lowest risk for heart disease was in the group of people who went to sleep between 10 p.m. and 10:59 p.m. It did not make any difference how many hours the person slept.
Did the study reveal any differences concerning sex, gender, or any other subgroups?
Yes. The connection between heart disease and sleep timing was stronger in women than in men. When researchers looked at the link between sleep timing and risk for heart disease, it did not make a difference whether patients had diabetes, high blood pressure, used tobacco products, or were overweight.
Did the authors express any possible reasons for their findings?
Other studies have shown that poor sleep is related to risk factors for heart disease, such as high blood pressure and obesity. Although this study found an association between sleep timing and heart disease, it did not establish a direct cause-and-effect relationship. Further research is needed to determine why sleep timing appears to change the risk for heart disease and how gender might influence that risk.
What were the strengths and shortcomings of this study's design and execution? Does it matter that the study subjects were from the United Kingdom and not the United States?
This was a relatively large study with more than 88,000 people. Sleep timing was accurate because of the use of the wrist-worn device rather than just a person trying to determine what time sleep started. However, the association between sleep timing and heart disease may not apply to all persons because the study participants were mostly White British individuals with a high socioeconomic status. Also, 58% of the people in the study were women and the average age was 61. So, the findings may not apply as well to men, young adults, or elderly people.
What, if anything, should people and health care professionals do differently in the face of these findings? What are the challenges to addressing this issue?
People should talk with their health care provider about their sleep habits and risk factors for heart disease. Healthy sleep requires that people sleep long enough and stay asleep without disturbances. However, sleep problems like insomnia and sleep apnea are very common. Hopefully, there will soon be additional research looking at what underlying factors account for the association between sleep timing and heart disease. More data on the influence of gender and sleep timing and heart disease can lead to the development of more precisely targeted and effective interventions.
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