In prior studies, scientists analyzed different variations of sleep patterns, including data on quality of sleep, sleep and wake times, as well as number of hours slept. Evidence suggests that there is a link between these concepts and health, performance, and cognitive functioning. This study and those similar to it have not yet been able to quantify the true role of regular sleep patterns, however.
New research out of Brigham and Women’s Hospital looked at academic performance in college students, while objectively measuring circadian rhythms and sleep. Findings indicate that irregular fluctuations between sleep and wakefulness are directly correlated with a lower grade point average, as well as a delayed release of melatonin (natural sleep hormone) and delayed sleep-wake timing. Findings are published in the June 12 issue of Scientific Reports.
Researchers analyzed the sleep diaries of 61 full-time Harvard undergraduates. Students recorded sleep patterns over a period of 30 days. This data helped researchers quantify sleep regularity with the SRI (sleep regularity index). This is a new metric, which was used to examine the relationship between sleep duration, sleep distribution throughout the day, SRI, and academic performance for one semester.
Lead author of the study, Dr. Andrew J.K. Phillips, from the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital, noted that these results indicate it is just as important to go to sleep and wake up around the same time as it is to get an adequate number of hours of sleep. He notes that sleep regularity may be an importable modifiable factor that is separate from sleep duration.
Researchers noted that students who had regular sleep patterns were more likely to have better grades; however, there were no significant differences in duration between students who were regular sleepers and those who had irregular patterns.
Another author of the paper, Dr. Charles A. Czeisler, who is the director of the Sleep Health Institute at Brigham and Women’s Hospital, noted that this research showed that the body’s biological clock shifted almost three hours later in students who had irregular sleep schedules, when compared to those who were more consistent with their sleeping patterns. These inconsistent sleep patterns mean that these students who were going to class at 9 a.m. had an internal body clock that was closer to 6 a.m. This time is notoriously linked to impaired performance in students. In the end, no time was saved because they slept just as much as those on a regular schedule, just not as consistent in the sleep and wake times.
Researchers measured the timing of melatonin release when students fell asleep. By doing so, scientists could look at the timing of the entire circadian rhythm. Of note, melatonin was released about 2.6 hours later in students who had sleep irregularity when compared to students who had regular sleep patterns.
Dr. Phillips noted that scientists used a mathematical model of the biological clock and could demonstrate the key difference between the sleep timing between students with regular and irregular sleep patterns. It was noted to be consistent with the various patterns of light exposure in each group. Those with regular sleep patterns got more light exposure during the day and much lower light levels at night than those students who had irregular sleep patterns. Most irregular sleepers slept more during the day and less at night.
The circadian clock, which is responsible for sleep-wake times, takes some time to adjust to any changes in schedule. It is sensitive and reacts to light exposure. Irregular sleepers often change their sleep patterns, as well as the amount of light exposure they receive daily, which led to a misalignment between the sleep-wake cycle and the circadian system.
Scientists note that light-based interventions may help with improving sleep regularity. These types of interventions include increasing their exposure to daylight and decreasing the amount of time they spend on light-emitting electronics before bedtime.