Poor Sleepers at Higher Risk of CVD, MESA Data Suggest

People who show the most variability in terms of how long they sleep and when they fall asleep are around twice as likely to develop cardiovascular disease over 5 years compared with solid sleepers, observational data from the Multi-Ethnic Study of Atherosclerosis (MESA) suggest.

The amount of variability it took to observe this increased risk—a standard deviation (SD) of > 90 minutes day-to-day across a weeklong test—wasn’t rare: four in 10 study participants met this bar for inconsistent sleep duration and one-quarter did so for bedtime.

Sleep regularity is a “marker for chronic circadian disruption and intermittent sleep deprivation,” lead author Tianyi Huang, ScD, MSc (Brigham and Women’s Hospital and Harvard Medical School, Boston, MA), and colleagues point out in their paper published this week ahead of the March 10, 2020, issue of the Journal of the American College of Cardiology.

Circadian rhythm is known to play an important role in cardiovascular functioning, such as in relation to heart rate or blood pressure, Huang told TCTMD. However, “prior studies on circadian disruption and cardiovascular disease mostly focused on shift workers, because we know that night shift work is a strong risk factor that can adversely affect the biological clock.”

Far less studied is “ubiquitous exposure” to poor sleep that occurs in the general population and has implications for public health, he explained. These results help fill that void, potentially offering a new means of CVD prevention.

Fluctuating Sleep Quality

Huang and colleagues studied the details of 1,992 MESA participants without CVD who had an average age of around 70 years at baseline. These individuals underwent 7-day wrist actigraphy between 2010 and 2013 and then were prospectively followed through 2016. Sleep regularity was determined by the SD on actigraphy of sleep duration and sleep-onset timing.

People with more versus less variation in sleep tended to have higher body mass index, blood pressure, and heart rate and were more likely to have diabetes, insomnia, daytime sleepiness, and sleep-disordered breathing. Compared to those with more-regular patterns, they also tended to get less REM sleep and to wake up more after falling asleep. Irregular sleep was more common among African-Americans, smokers, night workers, people who reported depression symptoms, and those who saw themselves as not being a so-called morning person.

In total, 111 individuals had nonfatal or fatal CV events over a median follow-up of 4.9 years: 35 MIs, 16 deaths due to coronary heart disease, 30 strokes, 17 other coronary events, and 13 other atherosclerotic or CVD deaths. The incidence rate was 11.8 per 1,000 person-years.

After adjusting for traditional CV risk factors and for sleep-related factors, the risk of incident CVD was highest for people whose amount and timing of sleep showed the most irregularity over the 7 days (P for trend = 0.002).

Incident CVD Risk Based on Standard Deviation of Sleep

These patterns held true when taking into account sex, race/ethnicity, average amount of sleep each day, and work schedule.

TVs, Mobile Phones, Social Media, and More

Writing in an editorial, Olaf Oldenburg, MD (Clemenshospital, Münster, Germany), and Jens Spiesshoefer, MD (Scuola Superiore Sant’Anna, Pisa, Italy, and University Hospital Muenster, Germany), say that Huang et al have identified novel risk factors for CVD. That such common sleep patterns appear to matter is “particularly striking,” they observe.

“The critical question arises as to how we can make further progress into our understanding of a potentially causal link between sleep and circadian rhythm, in particular, and CVD,” the editorialists stress.

Potential avenues include leveraging “big data” and wearable technologies as well as confirming these links through basic science, they suggest. Also, “any future demonstration that conservative measures, such as teaching sleep hygiene or using behavioral therapy, could improve sleep quality (and potentially even sympathovagal balance and daytime functional status) in patients with CVD would be an important breakthrough.”

It doesn’t take much to have irregular sleep, Huang noted. “Now there are so many things that can disrupt people’s sleep schedule. For example, many people have a TV in their bedroom and tend to use their mobile phone in bed. Some people even lie in the bed to read social media or [tablets].” Others may watch TV and fall asleep earlier or later depending on how engaged they are with what’s on the screen, Huang added.

Though there is always the potential for residual confounding, Huang said he is fairly confident that the relationships seen here are causative. “One thing I should mention,” he cautioned, “is the study sample is relatively small, so we cannot exclude the possibility of chance findings.”

Clinicians hoping to apply the study’s takeaways have an easy way to do so, Huang suggested: when discussing lifestyle strategies for CVD prevention like healthy diet and physical activity, they can encourage not only sufficient sleep but also a regular sleep schedule.