Irregular Sleep Schedules May Be as Bad as Getting Too Little Sleep

Having considerable variation in when you go to bed and when you wake up could increase your risk of depression as much as getting fewer hours of sleep overall, a new study in npj Digital Medicine suggests.

Researchers recruited 2,115 interns in physician-training programs, who tend to have high variability in terms of sleep schedules. Their sleep was tracked through a wearable device, daily mood through an app, and depression symptoms through questionnaires, over the course of a year.

Those with variable sleep schedules were more likely to score higher on standardized depression symptom questionnaires and report lower daily mood ratings. This was similar to those who got fewer hours of sleep or stayed up late.

These results were not surprising, since previous research has indicated that mood and depression can be strongly associated with sleep deficiency, according to the study’s lead author, Srijan Sen, MD, PhD, professor of psychiatry and director of the University of Michigan Depression Center. However, this research does highlight the potential role of sleep variability.

“These findings highlight sleep consistency as an underappreciated factor to target in depression and wellness,” he says.

Range of Health Risks

Getting too little sleep is often discussed for its negative health outcomes and for good reason. Studies have indicated that short sleep duration can increase risk of diabetes, for example. But irregular sleep patterns could have that effect too.

Research published in Diabetes Care found that lack of a regular bedtime can increase one's risk not only for diabetes, but also:

• Abdominal obesity
• High blood sugar
• Low HDL (good) cholesterol
• High triglyceride levels
• Hypertension

In that research, every hour of variability in the time one went to sleep was linked to a 23% greater chance of metabolic syndrome. Metabolic syndrome is a condition in which at least three of the five metabolic risk factors above are present, and it is linked with many serious health problems.

Establishing a New Habit

For some people, like shift workers, first responders, or the type of physician-in-training interns in the recent study, it’s almost impossible to tweak sleep schedule variations. But for many others, decreasing variability is just a matter of getting into a solid habit, says Mia Finkelston, MD, medical director at Online Care Group.

“We can handle some changes to our usual routine, but not as much as you might think,” she says. “Waiting to go to bed only when you’re tired can introduce too much unpredictability into your sleep schedule.”

Working from home during the COVID-19 pandemic has made this even more challenging for many people. When work can be done into the evening, that might lead to staying up later but still having to get up early to check in with the office. Also, many people try to catch up on shortened sleep on the weekends, which can cause more variability in sleep schedules.

That can make it difficult to fall asleep in general, increasing your rate of insomnia, which also brings mood and depression risk with it. “Your body and mind crave predictability when it comes to sleep, and when you get into a regular bedtime habit, it helps you wind down more quickly, fall asleep faster, and can even help sleep quality overall,” Finkleston says.

Morning Routines Help Too

In addition to establishing a regular bedtime, it’s also crucial to have a consistent wake-up time, even on the weekends, according to W. Christopher Winter, MD, president of Charlottesville Neurology and Sleep Medicine and author of The Sleep Solution.

"Sleeping in occasionally is fine, but regularly drowsing and hitting snooze could set you up for too much sleep variability overall," says Winter. "A better strategy might be taking a short nap on days when you feel tired," he adds.

Adding in other habits that make you feel refreshed can also help, Winter says, such as exercising in the morning and getting some sunshine and fresh air first thing.  

That’s because natural light can be a boon for resetting your body clock and even improving your mood. A study published in Sleep Health done with office workers who wore light-measuring devices found those who got natural light in the morning had increased sleep quality and reduced depression.

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