New research suggests that going to bed and waking up later on weekends than weekdays may have negative health consequences.
The new research was published in an abstract supplement of the academic journal Sleep.
Previous studies have suggested that social jet lag may have negative health consequences. Some have linked it to obesity, while others have suggested that social jet lag may raise the risk of atherosclerotic cardiovascular disease and diabetes.
The new research - led by senior author Michael A. Grandner, Ph.D., director of the Sleep and Health Research Program at the University of Arizona in Tucson - examined data from 984 adults aged between 22 and 60 years. The results were also presented at SLEEP 2017, which is the 31st Annual Meeting of the Associated Professional Sleep Societies, held in Boston, MA.
The data for the study were collected as part of the Sleep and Healthy Activity, Diet, Environment, and Socialization study, which is a community-based survey of more than 1,000 adults.
Dr. Grandner and colleagues evaluated social jet lag using the Sleep Timing Questionnaire, and they calculated it by subtracting the weekday sleep midpoint from the weekend one.
The researchers also assessed insomnia using the Insomnia Severity Index and accounted for additional factors that may have influenced the results, including age, sex, race and ethnicity, education, employment status, income, and sleep duration.
The participants reported their overall health using a standardized scale, choosing from the options "Excellent," "Good," or "Fair/Poor."
One hour of social jet lag raises heart disease risk by over 11 percent
The study revealed associations between social jet lag and worse mood, sleepiness, and fatigue, as well as poorer overall health.
More specifically, with each hour of social jet lag, the researchers found an 11.1 percent increase in the likelihood of developing heart disease.
Furthermore, every hour of social jet lag was associated with a 22.1 and 28.3 percent increase in the likelihood of having just "good" or "fair/poor" health, respectively, compared with "excellent" health.
The results did not depend on insomnia or sleep duration, so the jet lag on its own may be responsible for these health outcomes.
Lead author Sierra B. Forbush, an undergraduate research assistant in the Sleep and Health Research Program at the University of Arizona in Tucson, comments on the findings:
"These results indicate that sleep regularity, beyond sleep duration alone, plays a significant role in our health. This suggests that a regular sleep schedule may be an effective, relatively simple, and inexpensive preventative treatment for heart disease as well as many other health problems."
Additionally, the study found that high school graduates had greater social jet lag compared with college graduates, and that those in the highest income category had more minutes of social jet lag compared with their lower-earning counterparts.
The American Academy of Sleep Medicine (AASM) recommend that adults sleep for at least 7 hours each night for "optimal health."
Additionally, the AASM suggest that young adults, people who are trying to recover from a "sleep debt," and people who are ill, may all benefit from sleeping for longer than 9 hours per night.