Non-restorative sleep

Non-restorative sleep (NRS), also known as unrefreshing sleep,^[1] is a subjective symptom in which sleep is experienced as insufficiently refreshing and hence subjective sleep quality as poor.^[2][3][4] This can be despite the appearance of otherwise normal sleep, like adequate sleep duration and lack of nighttime awakenings.^[2][3] NRS is associated with daytime cognitive dysfunction, affective symptoms, fatigue, sleepiness, and increased pain sensitivity.^[2][3][5][4] It is diagnosed exclusively via self-report or sleep questionnaires.^[2][6]

Conditions

NRS is often a symptom of sleep disorders such as insomnia and shift work sleep disorder.^[2][3] It can also occur in hypersomnia and narcolepsy.^[2][3] In addition, NRS is frequently a symptom of conditions like fibromyalgia, myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), long COVID, autoimmune disorders like rheumatoid arthritis and systemic lupus erythematosus (SLE), and infections.^{[2][3][7][5][8][4]} NRS has been especially associated with fibromyalgia and ME/CFS, with approximately 65 to 95% of people with fibromyalgia and 85 to 95% of people with ME/CFS reporting unrefreshing sleep.^[2][3][5] NRS may in fact be related to the cognitive impairment, fatigue, and myalgia (muscle pain) experienced by people with fibromyalgia and ME/CFS.^[3][5][4] Other conditions associated with NRS include sleep apnea, periodic limb movement disorder (PLMD), and chronic pain.^[2][3][5] Psychiatric disorders such as depression or anxiety have been associated with NRS as well.^[2][3] On the other hand, NRS can occur without any comorbidity.^[2][3]

Correlates

Older age is strongly correlated with NRS, although conflicting findings exist.^[3] In addition, women experience NRS more often than men, though this is not always observed.^[3] Relatedly, in the case of fibromyalgia, more than 90% of people with this condition are women.^[2][5] People who are unemployed or retired have been found to experience more NRS than employed people.^[3] Shift workers have a relatively high level of NRS.^[3] Moderate to high stress has been associated with NRS.^[3]

Causes

Research on the mechanisms underlying NRS are controversial and inconclusive.^[2][3] NRS is correlated with sleep onset latency and to a lesser extent with sleep duration.^[3] The symptom might be due to disturbance of slow wave sleep (SWS; non-REM sleep or "deep sleep") and due to insufficiently deep sleep.^[3][2][5][4] Alternatively or additionally, it might be related to REM sleep deprivation.^[5] Pro-inflammatory cytokines such as interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor α (TNFα) may have negative effects on sleep and increase the likelihood of NRS.^[2] These findings provide a possible mechanism by which immune disorders and related conditions may affect sleep and cause NRS.^[2]

Treatment

See also: Hypnotic

There is little information available on treatment of NRS as of 2008.^[3][5] Treatments that might be helpful in some cases of NRS include behavioral measures like cognitive–behavioral therapy (CBT) and hypnotherapy, exercise, hypnotics, and certain antidepressants.^[5] Some hypnotics have been found to improve SWS, such as sodium oxybate (γ-aminobutyric acid; GHB)^[9][10] and gaboxadol,^[11][12] and hypnotics of this sort might be more useful than other hypnotics in the treatment of NRS, though more research is needed to substantiate such notions.^[5][13][4]