Understanding the definition and why it’s important for our health.
Regular sleep can be explained as being “not irregular” and vice versa. Sleep is naturally prone to be irregular, as it occurs in “chunks” that are loosely linked together, and these chunks occur preferably during the time we typically sleep—though more than an hour of variability in night-to-night sleep timing is probably abnormal.
The timing of sleep during the night is largely dependent on the light-dark cycle and the various rhythms linked to the 24-hour cycle, also known as circadian rhythms. Every day, there is a small “jiggling” of this overall positioning of the sleep chunks (or sleep cycles). Thus, what we consider regular sleep is actually a little bit irregular. Each night is not exactly the same. Exposure to light, noise, and too much temperature change while sleeping can also result in less regularity of sleep.
Regular sleep most importantly needs regular wake time and ample exposure to light on awakening. Darkness in the late evening after 8pm and during sleep is also important. Spending too much time in bed will make sleep less regular as the links between these sleep chunks will loosen and periods of wakefulness will emerge during the night. Some healthy individuals are naturally very regular, while some are irregular. Variable wake times and bedtimes make sleep irregular, somewhat like jet-lag without the need to travel. The extremes of age are less regular, with newborns sleeping in chunks around the clock and the elderly at risk for irregularity.
However, diseases such as depression, bipolar disease, pain, restless legs and sleep apnea can make sleep irregular. Increased irregularity of sleep timings have been associated with weight gain, depression, diabetes and heart disease. Regularity of sleep can be tracked in many ways these days. Examples include sleep diaries, activity monitoring devices, smartphone applications, cell phone/e-mail/social media use, smart mattresses and non-contact devices which use Wi-Fi or radar technology to track breathing, heart beats and body movements and estimate sleep and wake.
Simple ways to ensure regularity of sleep is to keep a stable light/dark cycle, have a consistent wake and bedtime, avoid eating late or during the night, and not spending more time in bed than one can sleep. Reducing time watching movies or using electronic media in bed—and certainly avoiding these if there is an awakening at night—is also a good idea. Sleep promoting drugs such as “sleeping pills” make sleep more regular, but we do not know if this is good or bad as more research is needed in this area. But what research has shown is that regular sleep leads to a healthier future. I look forward to a time when regular sleep is as common a phrase as balanced diet.
Robert J. Thomas, MD is an Associate Professor of Medicine at Harvard Medical School, Division of Pulmonary, Critical Care & Sleep Medicine, Department of Medicine, Beth Israel Deaconess Medical Center. He has been working in the field of sleep medicine and research for 26 years.