Rapid eye movement (REM) sleep, deep sleep, and sleep irregularity were significantly associated with increased risk for a range of chronic diseases, based on a new study of > 6000 individuals.
“Most of what we think we know about sleep patterns in adults comes from either self-report surveys, which are widely used but have all sorts of problems with over- and under-estimating sleep duration and quality, or single-night sleep studies,” corresponding author Evan L. Brittain, MD, of Vanderbilt University, Nashville, Tennessee, said in an interview.
The single-night study yields the highest quality data but is limited by extrapolating a single night’s sleep to represent habitual sleep patterns, which is often not the case, he said. In the current study, published in Nature Medicine, “we had a unique opportunity to understand sleep using a large cohort of individuals using wearable devices that measure sleep duration, quality, and variability. The All of Us Research Program is the first to link wearables data to the electronic health record at scale and allowed us to study long-term, real-world sleep behavior,” Dr. Brittain said.
The timing of the study is important because the American Heart Association now recognizes sleep as a key component of heart health, and public awareness of the value of sleep is increasing, he added.
The researchers reviewed objectively measured, longitudinal sleep data from 6785 adults who used commercial wearable devices (Fitbit) linked to electronic health record data in the All of Us Research Program. The median age of the participants was 50.2 years, 71% were women, and 84% self-identified as White individuals. The median period of sleep monitoring was 4.5 years.
REM sleep and deep sleep were inversely associated with the odds of incident heart rhythm and heart rate abnormalities. A higher percentage of deep sleep was associated with reduced odds of atrial fibrillation (OR, 0.87), major depressive disorder (OR, 0.93), and anxiety disorder (OR, 0.94).
Increased irregular sleep was significantly associated with increased odds of incident obesity (OR, 1.49), hyperlipidemia (OR, 1.39), and hypertension (OR, 1.56), as well as major depressive disorder (OR, 1.75), anxiety disorder (OR, 1.55), and bipolar disorder (OR, 2.27).
The researchers also identified J-shaped associations between average daily sleep duration and hypertension (P for nonlinearity = .003), as well as major depressive disorder and generalized anxiety disorder (both P < .001).
The study was limited by several factors including the relatively young, White, and female study population. However, the results illustrate how sleep stages, duration, and regularity are associated with chronic disease development, and may inform evidence-based recommendations on healthy sleeping habits, the researchers wrote.
Findings Support Need for Sleep Consistency
“The biggest surprise for me was the impact of sleep variability of health,” Dr. Brittain told this news organization. “The more your sleep duration varies, the higher your risk of numerous chronic diseases across the entire spectrum of organ systems. Sleep duration and quality were also important but that was less surprising,” he said.
The clinical implications of the findings are that sleep duration, quality, and variability are all important, said Dr. Brittain. “To me, the easiest finding to translate into the clinic is the importance of reducing the variability of sleep duration as much as possible,” he said. For patients, that means explaining that they need to go to sleep and wake up at roughly the same time night to night, he said.
“Commercial wearable devices are not perfect compared with research grade devices, but our study showed that they nonetheless collect clinically relevant information,” Dr. Brittain added. “For patients who own a device, I have adopted the practice of reviewing my patients’ sleep and activity data which gives objective insight into behavior that is not always accurate through routine questioning,” he said.
As for other limitations, “Our cohort was limited to individuals who already owned a Fitbit; not surprisingly, these individuals differ from a random sample of the community in important ways, both demographic and behavioral, and our findings need to be validated in a more diverse population,” said Dr. Brittain.
Looking ahead, “we are interested in using commercial devices as a tool for sleep interventions to test the impact of improving sleep hygiene on chronic disease incidence, severity, and progression,” he said.
Device Data Will Evolve to Inform Patient Care
“With the increasing use of commercial wearable devices, it is crucial to identify and understand the data they can collect,” said Arianne K. Baldomero, MD, a pulmonologist and assistant professor of medicine at the University of Minnesota, Minneapolis, in an interview. “This study specifically analyzed sleep data from Fitbit devices among participants in the All of Us Research Program to assess sleep patterns and their association with chronic disease risk,” said Dr. Baldomero, who was not involved in the study.
The significant relationships between sleep patterns and risk for chronic diseases were not surprising, said Dr. Baldomero. The findings of an association between shorter sleep duration and greater sleep irregularity with obesity and sleep apnea validated previous studies in large-scale population surveys, she said. Findings from the current study also reflect data from the literature on sleep duration associated with hypertension, major depressive disorder, and generalized anxiety findings, she added.
“This study reinforces the importance of adequate sleep, typically around 7 hours per night, and suggests that insufficient or poor-quality sleep may be associated with chronic diseases,” Dr. Baldomero told this news organization. “Pulmonologists should remain vigilant about sleep-related issues, and consider further investigation and referrals to sleep specialty clinics for patients suspected of having sleep disturbances,” she said.
“What remains unclear is whether abnormal sleep patterns are a cause or an effect of chronic diseases,” Dr. Baldomero noted. “Additionally, it is essential to ensure that these devices accurately capture sleep patterns and continue to validate their data against gold standard measures of sleep disturbances,” she said.
The study was based on work that was partially funded by an unrestricted gift from Google, and the study itself was supported by National Institutes of Health. Dr. Brittain disclosed received research funds unrelated to this work from United Therapeutics. Dr. Baldomero had no financial conflicts to disclose.
A version of this article first appeared on Medscape.com.