Irregular sleep schedules connected to bad moods and depression, study shows

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An irregular sleep schedule can increase a person’s risk of depression so much in the long run that they get fewer hours of sleep overall or stay up late most nights, according to a new study.

Even if it’s just about their mood the next day, people who wake up differently from day to day may be in a bad mood as those who got up extra late the night before or got up extra early that morning. The study shows.

The study, conducted by a team from Michigan Medicine, the University of Michigan’s academic medical center, used data from direct measurements of sleep and mood from more than 2,100 doctors in early careers over a year. It is published in npj Digital Medicine.

The interns, as they are called in their first year of training after studying medicine, all experienced the long, intensive working days and irregular working hours that are the hallmarks of this period in medical training. These factors, which changed from day to day, altered their ability to have regular sleep schedules.

The new paper is based on data collected by tracking the interns’ sleep and other activities on their wrists through commercial devices, asking them to report their daily mood in a smartphone app and taking quarterly tests for signs of depression.

Those whose devices showed they had variable sleep schedules were more likely to score higher scores on standardized depressive symptoms questionnaires and had lower daily mood ratings. Those who regularly stayed up late or had the fewest hours of sleep also scored higher for symptoms of depression and lower scores for daily mood. The results complement what is already known about the relationship between sleep, daily mood, and long-term depression risk.

“The advanced wearable technology enables us to study the behavioral and physiological factors of mental health, including sleep, on a much larger scale and more precisely than before, which opens up an exciting field for us,” said Yu Fang, director of MSE Author of the new paper and research specialist at the Michigan Neuroscience Institute. “Our results not only aim to control self-management with regard to sleeping habits, but also to inform institutional planning structures.”

Fang is part of the Intern Health Study team led by Dr. Srijan Sen, who has been researching first year medical professionals’ mood and depression risk for more than a decade. The study collected an average of two weeks of data prior to the beginning of the doctors’ internship years and an average of nearly four months of monitoring during their internship year.

For the new paper, the team worked with Cathy Goldstein, MD, MS, an associate professor of neurology and a physician at Michigan Medicine’s Sleep Disorders Center.

She notes that wearable devices that value sleep are now used by millions of people, including the Fitbit devices, other activity trackers, and smart watches used in the study.

“With these devices we can for the first time record sleep over longer periods of time without any effort for the user,” says Goldstein. “We still have questions about the accuracy of the sleep predictions that consumer trackers make, although initial work suggests similar performance to clinical and research-grade actigraphy devices that have been approved by the FDA.”

Sen, who holds the Eisenberg Professorship of Depression and Neuroscience and is Professor of Neuroscience and Psychiatry, notes that the new findings build on his team’s work on new doctors’ high risk of depression and other related factors at increased risk.

“These results highlight sleep consistency as an underestimated factor in depression and well-being,” he says. “The work also underscores the potential of wearable devices to understand important health-related constructs that we have not previously been able to study on a large scale.”

The team notes that the relatively young group of people in the study – with an average age of 27 and a college degree and medical degree – is not representative of the wider population. Since all of them have similar workloads and schedules, they are a good group to use to test hypotheses. The researchers hope that other groups will study other populations with similar equipment and approaches to see if the sleep schedule variation results hold up for them.

For example, Fang notes that parents of young children could be another important group to study. “I also wish my 1-year-old could find out about these findings and only wake me at 8:21 am every day,” she jokes.

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More information:
npj Digital Medicine, DOI: 10.1038 / s41746-021-00400-z Provided by the University of Michigan

Quote: Irregular sleep schedules related to bad mood and depression, study results (2021, February 18), accessed February 18, 2021 from

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