Researchers from Boston’s Brigham and Women’s Hospital reported that people whose sleep is irregular have twice the risk of developing cardiovascular diseases compared to people whose sleep is more regular. The investigators reached this conclusion after looking at data from 1,992 participants in the federally funded Multi-Ethnic Study of Atherosclerosis. None of the participants, whose ages ranged from 45 to 84, had heart disease when the study began. They were a diverse group – 38 percent white, 28 percent African American, 22 percent Hispanic, and 12 percent Chinese American.
All the participants wore a wrist activity tracker for seven days. It recorded their bedtime, the duration of their sleep and the time they woke. They were then followed for an average of 4.9 years, during which 111 had a heart attack, stroke or other adverse cardiovascular event.
Based on this data, the researchers divided the participants into four groups: those with the most irregular sleep (characterized by two or more hours difference in sleep duration each night); those with the most regular sleep patterns (less than an hour’s difference in sleep duration nightly); those whose bedtimes were most consistent (less than a 30-minute difference each night); and those with the most inconsistent bedtimes (nightly differences of 90 minutes or more).
Those with the most irregular patterns had a two-fold increased risk of cardiovascular events. After analyzing these findings the researchers estimated that only eight of every 1,000 people whose sleep pattern was most regular would have a cardiovascular event per year. They also estimated that out of 1,000 people whose sleep patterns are the most irregular, 20 people would likely develop a cardiovascular event over a one-year period.
The study’s lead author, Tianyi Huang, D.Sc., noted that when we talk about interventions to prevent heart attacks and stroke: “We focus on diet and exercise. Even when we talk about sleep, we tend to focus on duration – how many hours a person sleeps each night – but not on sleep irregularity and the impact of going to bed at different times or sleeping different amounts from night to night. Our study indicates that healthy sleep isn’t just about quantity but also about variability, and that this can have an important effect on heart health.” He said his team would like to perform another study to see whether changing sleep patterns by going to bed consistently each night can reduce the risk of future cardiovascular events.
We know that adequate sleep is key to a healthy lifestyle, and accumulating research suggests that it plays an even larger role in health than we once thought. Earlier research has suggested that sleeping less than six hours a night is associated with obesity, smoking, excess alcohol consumption, and the likelihood of being less physically active.
Andrew Weil, M.D.
Tianyi Huang et al. “Actigraphy-measured Sleep Regularity and Risk of Incident Cardiovascular Disease: The Multi-Ethnic Study of Atherosclerosis” Journal of the American College of Cardiology, March 2020 DOI: 10.1016/j.jacc.2019.12.054