Investigating next steps
In additional analyses, Dr. Full and colleagues found that sleep duration regularity continued to be associated with high coronary artery calcium burden and abnormal ankle-brachial index when accounting for severe obstructive sleep apnea, average nightly sleep duration, and average sleep fragmentation.
Notably, when sleep duration was added, all participants with more irregular sleep durations (SD > 60 minutes) were more likely to have a high coronary artery calcium burden, compared with those with regular sleep durations (SD < 60 minutes). The results remained when participants who reported shift work, including night shift work, were excluded.
Additional studies are needed to understand the mechanisms, the study authors wrote. Night-to-night variability in sleep duration and sleep timing can cause desynchronization in the sleep-wake timing and circadian disruption.
“A key issue highlighted in this study is that sleep irregularity itself, independent of how much sleep people were getting, was related to heart health. Sleep is a naturally recurring phenomenon, and maintaining regularity helps provide stability and predictability to the body,” Michael Grandner, PhD, associate professor of psychiatry and director of the sleep and health research program at the University of Arizona, Tucson, said in an interview.
Dr. Grandner, who wasn’t involved with this study, has researched sleep irregularity and associations with cardiovascular disease, diabetes, obesity, and many other adverse outcomes.
“When people have very irregular sleep schedules, it may make it harder for the body to optimally make good use of the sleep it is getting, since it such a moving target,” he said. “The unique angle here is the ability to focus on regularity of sleep.”
The study was supported by the National Heart, Lung, and Blood Institute and the National Center for Advancing Translational Sciences of the National Institutes of Health. One author received grants and consulting fees from pharmaceutical companies unrelated to the research. The other authors and Dr. Grandner disclosed no relevant financial relationships.
A version of this article originally appeared on Medscape.com.