Irregular Bedtimes Lead to Poorer Mental Performance: Study


Put your sleep-wake cycle on a regular rhythm and you may find more success at work or at school.

A new study from researchers at Brigham and Women’s Hospital in Boston assessed 61 Harvard students over a 30-day period and discovered that irregular sleep-and-wake times led to a significant decrease in academic performance.

The research suggests that regular sleep cycles are critical to achieving high levels of mental acuity and work ability.

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“Our results indicate that going to sleep and waking up at approximately the same time is as important as the number of hours one sleeps,” said lead author Dr. Andrew J. K. Phillips, a biophysicist at the Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital in Boston.

While public health guidelines call for a baseline amount of hours that one sleeps to maintain a healthy lifestyle — typically about eight hours — the new study shows that a person’s sleeping cycle should also be taken into consideration.

“Sleep regularity is a potentially important and modifiable factor independent from sleep duration,” Phillips said.

Upsetting the Body’s Clock

When a person goes to sleep at different times throughout the week, the body’s circadian rhythm tends to go off course, shows the study. That’s because the release of melatonin, a hormone that lets the body know it’s time to sleep, is delayed in non-routine sleepers.

The researchers found that, in study participants who didn’t keep to a regular sleep schedule, the release of melatonin was delayed several hours compared to regular sleepers.

“We found that the body clock was shifted nearly three hours later in students with irregular schedules as compared to those who slept at more consistent times each night,” said senior author Dr. Charles A. Czeisler, Director of the Sleep Health Institute at Brigham and Women’s Hospital.

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The subtle but important shift in the body’s hormone levels creates a physical environment where a person’s internal clock is way off-kilter, note the researchers.

“For the students whose sleep and wake times were inconsistent, classes and exams that were scheduled for 9 a.m. were therefore occurring at 6 a.m. according to their body clock, at a time when performance is impaired. Ironically, they didn’t save any time because in the end they slept just as much as those on a more regular schedule,” said Dr. Czeisler.

The researchers noted that a person’s exposure to light was directly tied to his or her internal clock.

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“Using a mathematical model of the circadian clock, we were able to demonstrate that the difference in circadian timing between students with the most irregular sleep patterns and students with regular sleep patterns was consistent with their different patterns of daily light exposure,” said Phillips.

“In particular, regular sleepers got significantly higher light levels during the daytime, and significantly lower light levels at night than irregular sleepers who slept more during daytime hours and less during nighttime hours,” added Phillips.

Previous research has shown that exposure to light from electronic devices, such as a cell phone or computer, can impair sleep.

The study appeared in the journal Scientific Reports.