Nonrestorative sleep: symptom or unique diagnostic entity?

Nonrestorative sleep (NRS) refers to the subjective experience of sleep as insufficiently refreshing, often despite the appearance of normal sleep according to traditionally assessed objective parameters. This has led researchers to pursue alternative physiological markers of nonrestorative or unrefreshing sleep, though much of this research remains controversial and inconclusive. This review summarizes the recent findings on NRS in the literature and discusses some of the issues inherent in current efforts to define and measure NRS. We offer a summary of recommended clinical approaches to NRS and discuss a new potential paradigm for the assessment of NRS-an approach modelled on current diagnosis of insomnia.