Interrupted Sleep? No Wonder You’re Moody

Those of us in sleep medicine are very familiar with the effects of sleep deprivation. Many studies have shown us the problems associated with insufficient sleep. However, what happens to those of us whose sleep is disrupted for five or ten minutes at a time several times a night? This has never been studied despite the fact that it is a common occurrence in our day-to-day lives. The classic example being the parent who needs to tend to a child during the night. In fact, in a recent survey, 20% of parents of newborn to three-year-olds reported an average of three or more awakenings per night.

In a study published this month in the journal Sleep Medicine, researchers set out to find just what consequences this might have on mood and vigilance. Vigilance is defined as the ability to maintain attention and alertness over prolonged periods.

A group of students with no prior sleep problems was recruited. They were tested as to mood and vigilance one hour after awakening. These tests were performed under three different conditions. First, they were tested after eight hours of uninterrupted sleep. Then after their sleep had been restricted to four hours, and finally after a night in which they were awakened for a period of 10 minutes every 90 minutes. During this 10-minute period, they were assigned a task on a computer and then allowed to return to sleep.

As expected, when sleep was restricted to four hours, vigilance decreased. Moodiness, as indicated by depression, fatigue, and reduced vigor, increased significantly. However, what was most interesting was that their scores were just as bad after a night of brief awakenings. In other words, brief interruptions of sleep had the same negative impact on mood and vigilance as did a night of severe sleep restriction.

I think this is a very important study. So many of us, such as parents, shift workers, and physicians, have our sleep interrupted for short periods throughout the night. This study demonstrates the adverse effects of just one night. Imagine what the cumulative results on a parent of an infant or young child or a physician on call might be? I think it is obvious that it has to negatively affect their ability to function at the highest level.

What is the take home message? I think we need to have a greater appreciation for the adverse influence on function of interrupted sleep. In the case of parents, I think this study makes a great example for shared parental responsibility. Looking back to when I was a physician on call, it was common to get several requests a night requiring my full attention. I can remember that after such a night I was more irritable and not at my best the next day. Based upon this study, maybe a day off after such a night might have been in everyone’s best interest.

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