Some evidence does suggest that irregular sleep has an adverse impact on health. The most recent study of this subject, from Boston’s Brigham and Women’s Hospital, found that people who don’t have regular bedtimes and get varying amounts of sleep each night have a higher risk of obesity, high cholesterol, high blood pressure, high blood sugar, and other metabolic disorders. The researchers reported that for every hour of variability in the time a person goes to bed and spends asleep, there’s a 27 percent greater chance of experiencing a metabolic abnormality
To reach that conclusion, the researchers followed 2,003 adults ages 45 to 84 who already were enrolled in a study of atherosclerosis funded by the National Heart, Lung and Blood Institute. The participants were tracked for a median of six years to explore the links between sleep regularity and metabolic abnormalities. The participants wore actigraph wrist watches for seven days, kept a sleep diary and responded to questionnaires about their sleep habits as well as other lifestyle and health factors.
Participants whose sleep duration varied by more than one hour were more likely to be African-Americans, to work non-day shift schedules, smoke and have shorter sleep duration. They also had more depressive symptoms, higher total intake of calories and a higher rate of sleep apnea.
Study leader Tianyi Huang, an epidemiologist, said that while many earlier studies showed a link between insufficient sleep and higher risks of obesity, diabetes and other metabolic disorders, “we didn’t know much about the impact of irregular sleep, high day-to-day variability in sleep duration and timing.”
The researchers found that variation in sleep duration and bedtime preceded the development of metabolic dysfunction, suggesting a causal link between the two.
A similar study from Duke University Medical Center published in September 2018 came to many of the same conclusions. It reported that people with irregular sleep patterns weighed more, had higher blood sugar, higher blood pressure, and a higher projected risk of having a heart attack or stroke within 10 years than those who slept and woke at the same time daily. That study included 1,978 adults ages 54 to 93 and also found that those with irregular sleep schedules as determined by actigraph watches and sleep diaries were more likely to report depression and stress. Here, too, African-Americans had the most irregular sleep patterns compared to others in the study. The Duke researchers said their findings showed an association, but not a cause-and-effect relationship, between sleep regularity and heart and metabolic health.
Study leader Jessica Lunsford-Avery, Ph.D. suggested that there might be something about obesity that disrupts sleep regularity or “perhaps poor sleep interferes with the body’s metabolism, which can lead to weight gain…With more research, we hope to understand what’s going on biologically and perhaps then we could say what’s coming first.”
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Andrew Weil, M.D.
Tianyi Huang et al, “Cross-sectional and prospective associations of actigraphy-assessed sleep regularity with metabolic abnormalities: The Multi-Ethnic Study of Atherosclerosis.” Diabetes Care, June 5, 2019 DOI: 10.2337/dc19-0596
Jessica R. Lunsford-Avery et al, “Validation of the Sleep Regularity Index in Older Adults and Associations with Cardiometabolic Risk”. Scientific Reports September 21, 2018, DOI: 10.1038/s41598-018-32402-5