A widely-accepted hypothesis in sleep theory is being challenged by a recent study. The so-called “sleep debt theory”, which states that we can actually “make up” for lost sleep, has been in vogue for the past few decades. But the findings of a new study recently published in the American Journal of Physiology (AJP) show the sleep debt theory just might need some revision.
Participants in the study experienced four nights of eight hours of sleep (considered baseline), six nights of six hours of sleep (considered restricted), and three nights of 10 hours of sleep (considered recovery). Sleep debt theory predicts that, following the recovery sleep periods, the participants would experience restored attention levels and healthy levels of cortisol and interleukin-6 (blood markers that measure stress levels and inflammatory response, respectively).
The results were mixed. Interleukin-6 levels were reduced after the “recovery” period, but cortisol levels were not. And neither was the overall attention deficiencies incurred by the “restricted” periods (as measured by a series of physical and cognitive tasks).
Based on this study, sleep debt theory is only about half right. Which, in the scientific world, just doesn’t cut it.
The stakes are high in the field of sleep study. Physiologically speaking, chronically elevated stress levels (as indicated by cortisol levels) are a major health risk. And economically speaking, decreased attention and impaired cognition due to poor sleep have been shown to cost millions (and possibly billions) of dollars in lost productivity. Clearly, sleep quantity is an important issue.
But what about sleep quality?
For the average person in their home, getting six, eight, or even 10 hours of sleep is no guarantee that those hours are restful sleep. Quality sleep occurs when a regular pattern of REM (rapid-eye movement) cycles is allowed to occur throughout the night. But any number of things can interrupt this cycle without fully awakening the sleeper.
For example, the American Chiropractic Association estimates that as many as nine out of 10 Americans suffer from back pain of some kind. Studies have linked flat mattresses to chronic back pain. If a person goes to bed, hoping to gain respite from their back pain, but the very mattress underneath them is the cause of that back pain, the quality of sleep will naturally suffer, whether for six hours or 12 hours.
The debate of quality versus quantity will continue. But thanks to studies such as the one published in the AJP, science can continue to zero in on the problem. Hopefully, knowing that will help us all sleep a little better at night.