From ancient times, sleep has been valued as a restorative time, making the person feel energized and refreshed. Modern science has show this isn’t just a subjective feeling. During sleep the immune system and the cardiovascular system experience a reprieve which could be called a restoration, and other organ systems are restored.
But psychologists, medics, and everyone who works with insomniac know: some sleep doesn’t feel restorative. Subjects can know they have slept 6 or more hours a night but still feel inadequately refreshed. What are they doing wrong? They get plenty of sleep and don’t get one of the main benefits of sleep? Remember, there is no viable biomarker for sleepiness and only behavioral ones for alertness and vigilance, so we must rely on the subjective reports of the problem sleepers.
Non-restorative sleep must be considered poor quality sleep.
The medical and research fields are somewhat divided about the concept of Non-restorative sleep as a "thing" – a sleep disorder or a part of insomnia worth defining and keeping in the medical lexicon. It shows up in diagnostic manuals and scientific literature even if there is no formal definition.
Pople with NRS score lower on daytime tests of vigilance and motor skills and are more likely to describe themselves as being in pain or fatigued. They have more fragmented sleep, even if they don’t know it – polysomnograms show micro-awakenings. However, for the most part, polysomnography shows similar patterns to those of normal sleepers. Whatever is causing the NRS does not show up in conventional diagnostics.
Not only is Nonrestortive Sleep a component of insomnia, it can result in daytime sleepiness even in people who apparently have no problem falling or staying asleep. Howver, if there is any definition of NRS it is the subjective feeling of being unrefreshed even after normal sleep and without any sleep disorder.
Can NRS be treated? It’s difficult. Cognitive behavioral therapy directly addresses getting to and staying asleep. The Z-drugs also affect sleep duration and maintenance. They are not likely to have an impact on NRS. Drugs that make a person sleep deeper (e.g. sodium oxybate) are a possibility, but they are not widely used for this purpose, and there is no evidence that a shortage of slow-wave sleep is necessarily the problem for people with NRS. Daytime exercise and a cool room for sleeping appear to be effective for some people.
Nonrestorative sleep may be one of those "hidden in plain sight" problems in healthcare. With no formal diagnostic category, it is not always taken seriously although it seems a problem for millions. Like so much in science “more research is needed” but this type of problem has to compete with other conditions and the most recent National Sleep Disorders Research Plan does not mention this type of problem.