Non-Restorative Sleep

Epidemiology of Non-Restorative Sleep in the General PopulationPDF icon

Non-restorative sleep (NRS) is one of the sleep disturbances that define insomnia. It affects nearly 10% of the general

Associations between non-restorative sleep, mental disorders and daytime consequences were investigated in 8937 non-institutionalized individuals aged 18 or over living in California, New York or Texas. A total of 15.4% of the sample reported NRS.

Prevalence was 1.5 times higher among women than men. After adjusting for age and gender, it was found that having a major depressive disorder (OR: 4.3), anxiety disorder (OR: 2.1) or a bipolar disorder (OR: 3.2) was associated with NRS. Having a physical disease was also associated with NRS but not as strongly than mental disorders. Subjects with NRS were also more likely to complain that their sleep problem had deleterious effects on their daytime functioning compared to DIS/DMS subjects.

NRS concerns one on seven individuals and has important consequences on daytime functioning of affected individuals. Treatment objectives should focus on the restorative quality of sleep and daytime functioning.

Is There a Role of the Circadian Timing System in Unrestorative Sleep?PDF icon

The circadian timing system in humans drives/modulates the 24-hour-variation in physiology and behavior including sleep-wake. Detrimental effects of shift work on human health as well as the sleep-wake-cycle have been repeatedly reported, although the mechanisms behind have to be clarified in future studies.

Recent results have shown that application of every-day light in the early evening as well as many other factors of our daily life are able to influence circadian rhythmicity as well as melatonin excretion. A melatonin deficit on an individual basis is associated with specific changes in sleep and exogenous melatonin has shown to specifically influence circadian components of sleep. Moreover, exogenous melatonin has shown to improve daytime functioning in patients suffering from primary insomnia.

Thus, it needs to be determined whether one cause of a group of patients suffering from unrestorative sleep is a weakening of the circadian timing system, caused by environmental influences such as light at the wrong time, which could be specifically addressed in future therapeutic approaches.

Approaches to the Polysomnography Study of Non-Restorative Sleep

While the polysomnograpchic correlates of sleep induction and sleep maintenance are well defined, the more "qualitative" aspects of sleep are not as clearly understood or measured. Examples of terms used to describe the qualitative aspects of sleep are: Sleep Quality, Restorative Value of Sleep, Consolidated Sleep, and Depth of Sleep. There have been attempts to quantify two of these qualitative aspects of sleep. Depth of sleep has been studied by attempting to determine auditory awakening thresholds (AAT). AAT varies as a function of sleep continuity, sleep stage, and sleep deprivation, sedating drugs as well as sleep disorders. What is not known is whether patients and subjects can subjectively identify depth of sleep and whether AAT correlates with the perception of sleep quality or some other positive attribute of sleep. Sleep continuity has been investigated by evaluating the frequency and density of arousals from sleep. Sleep fragmentation is associated with sleep disorders, alerting drugs, and environmental challenges. Increased sleep fragmentation reverses the "restorative" value of sleep as evidenced by increased daytime sleepiness (decreased alertness), and impaired performance. In many ways it can be though of as the functional equivalent of sleep loss. Sleep quality has been used in clinical trials to assess the efficacy of hypnotics. Many BzRAs have been shown to increase patients' perception of the quality of sleep. Interestingly in many of these trials, while sleep quality was impacted by phamacotherapy, the depth of sleep or the refreshing value of sleep was not rated as different on drug versus placebo nights. In these trials, sleep quality is simply defined as the answer to the question: how would you rate the quality of your sleep last night. Attempts to correlate answers to this question with sleep parameters have not produced robust associations. Correlations, when present, were typically between sleep quality and total sleep time. Most importantly there were no attempts to relate changes in the perception of sleep quality with aspects of daytime function. Research on the restorative nature of sleep has taken many routes. There are a series of papers on non-restorative sleep. These papers typically use this term in association with sleep in certain types of pain conditions. The hypothesis in these studies is that these disorders don't necessarily shorten sleep length as much as they the decrease they produce fundamental changes in the nature of sleep thereby making sleep less restorative. It is important to note that the DSM IV gives the same weight to non-refreshing sleep as to difficulty falling asleep or staying asleep in defining insomnia. In this area there are some knowns and some unknowns. It is known that individual complain of sleep disturbance in the absence of any perception of or PSG evidence of difficulty falling asleep or staying asleep. Thus it can be concluded that non-restorative sleep is a real clinical phenomenon. What is not known is: 1. Is the use of the term non-restorative sleep the same across patients and across disorders? 2. Is there a scale, which can identify and quantify this aspect of sleep? 3. Is there a polysomnigraphic correlate of non-restorative non-refreshing sleep? 4. Is there an impact of non-restorative sleep on any aspects of daytime functionality?

Non-Restorative Sleep and Insomnia in KoreaPDF icon


  1. To determine the prevalence of insomnia symptoms in the Korean general population;
  2. To examine their evolution in the general population between 2001 and 2008.


  • 1/8 individuals reported insomnia symptoms in 2008 and 1/6 individuals in 2001;
  • Prevalence of OSAS has significantly increased in 8 years both in men and in women
  • 1/20 men and 1/38 women have OSAS.

Is Non-Restorative Sleep Different in Older Adults?PDF icon

The aging process interacts with aspects of sleep in complex ways. For example, while the prevalence of sleep-related complaints, per se, increases significantly with age, the prevalence of diagnosed insomnia does not (Ohayon, Sleep Medicine Reviews 2002). This suggests that the experience of non-restorative sleep in older adults may not be the same as that reported by younger adults. Here we explore this possibility. The study sample was composed of 8,937 community-dwelling individuals, aged > 18, who formed a representative sample of the populations of the states of California, New York and Texas collected at Stanford University with the Sleep-EVAL System. 1593 individuals in this sample were aged > 65. Subjects were interviewed by telephone. The interviews included sleeping habits, health, sleep and mental disorders. The associations among difficulty initiating sleep (DIS), difficulty maintaining sleep (DMS), non-restorative sleep (NRS), sleep dissatisfaction, napping, age, health status, sleep apnea, depression, anxiety and cognitive impairment were examined. Compared to individuals reporting either DIS or DMS, individuals reporting NRS were significantly (p < .0001) more likely to report: poor health status, sleep dissatisfaction, sleep apnea, depression, anxiety, excessive daytime sleepiness and cognitive difficulties. NRS was significantly (p < .0001) less prevalent in older adults, declining from 16.1% in the 18-44 yr group to 7.4% in the > 65 yr group. Compared to younger adults reporting NRS, older adults reporting NRS were significantly (p < .0001) less likely to report: sleep dissatisfaction, sleep apnea, depression, anxiety, or cognitive difficulties. Compared to younger adults reporting NRS, older adults reporting NRS were significantly (p < .0001) more likely to report napping. Associations of DIS/DMS or of NRS with Health Status and with EDS were unaffected by age. The markedly different pattern of associations between NRS and the other measures of interest observed in older compared to younger adults suggests that the experience of NRS by older adults may be considerably different from that of younger adults.