title: Pain sensitivity and modulation in primary insomnia.
abstract: Sleep of good quantity and quality is considered a biologically important resource necessary to maintain homeostasis of pain-regulatory processes. To assess the role of chronic sleep disturbances in pain processing, we conducted laboratory pain testing in subjects with primary insomnia. Seventeen participants with primary insomnia (mean ± SEM 22.6 ± 0.9 yrs, 11 women) were individually matched with 17 healthy participants. All participants wore an actigraph device over a 2-week period and completed daily sleep and pain diaries. Laboratory pain testing was conducted in a controlled environment and included (1) warmth detection threshold testing, (2) pain sensitivity testing (threshold detection for heat and pressure pain), and (3) tests to access pain modulatory mechanisms (pain facilitation and inhibition). Primary insomnia subjects reported experiencing spontaneous pain on twice as many days as healthy controls during the at-home recording phase (p < 0.05). During laboratory testing, primary insomnia subjects had lower pain thresholds than healthy controls (p < 0.05 for heat pain detection threshold, p < 0.08 for pressure pain detection threshold). Unexpectedly, pain facilitation, as assessed with temporal summation of pain responses, was reduced in primary insomnia compared to healthy controls (p < 0.05). Pain inhibition, as assessed with the diffuse noxious inhibitory control paradigm (DNIC), was attenuated in insomnia subjects when compared to controls (p < 0.05). Based on these findings, we propose that pain-inhibitory circuits in patients with insomnia are in a state of constant activation to compensate for ongoing subclinical pain. This constant activation ultimately may result in a ceiling effect of pain-inhibitory efforts, as indicated by the inability of the system to adequately function during challenge.
authors.affiliation: Beth Israel Medical Deaconess Center & Harvard Medical School, Boston, MA, USA. mhaack@bidmc.harvard.edu
authors.forename: M
authors.initials: M
authors.lastname: Haack
authors.forename: J
authors.initials: J
authors.lastname: Scott-Sutherland
authors.forename: G
authors.initials: G
authors.lastname: Santangelo
authors.forename: N S
authors.initials: NS
authors.lastname: Simpson
authors.forename: N
authors.initials: N
authors.lastname: Sethna
authors.forename: J M
authors.initials: JM
authors.lastname: Mullington
mesh_terms: D000328:Adult; D002908:Chronic Disease; D003213:Conditioning, Psychological; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D005528:Foot; D006358:Hot Temperature; D006801:Humans; D007101:Immersion / Q000503:physiopathology; D008297:Male; D010146:Pain / Q000523:psychology*; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology; D011312:Pressure; D007319:Sleep Initiation and Maintenance Disorders / Q000150:complications* / Q000523:psychology*; D011795:Surveys and Questionnaires; D055815:Young Adult