Insomnia, sleep quality, pain, and somatic symptoms: Sex differences and shared genetic components

This study investigated the sex differences, and the shared genetic and environmental factors underlying the associations of sleep disturbances (insomnia and sleep quality) with pain and somatic symptoms in both adolescents and middle-aged adults. We recruited 259 adolescents (69 with current insomnia) and their parents (256 middle-aged adults, 78 with current insomnia). Insomnia severity and sleep quality were measured by the Insomnia Severity Inventory (ISI) and Pittsburgh Sleep Quality Index (PSQI), respectively. Pain and somatic symptoms were measured by the Somatic Symptom Inventory and Visual Analogue Scale for overall pain. Subjects with insomnia scored higher on all measures of pain and somatic symptoms than non-insomnia patients, in both adolescents and adults (P < .001). Both pain and somatic measures were associated with ISI and PSQI scores after controlling for age, sex, depressive and anxiety symptoms. There was an interaction effect between insomnia and female sex on pain and somatic symptoms (P < .05), especially in adults. Pain and somatic symptoms ran in family with moderate heritability (range h(2) = 0.15-0.42). The phenotypic associations of ISI and PSQI with pain and somatic measures were both contributed by genetic (range p(G) = 0.41-0.96) and environmental (range p(E) = 0.27-0.40) factors with a major genetic contribution. In summary, insomnia and poor sleep quality are closely associated with pain and somatic symptoms. Insomnia seems to modulate the sex differences in pain and somatic symptoms, especially in the adult population. A shared genetic predisposition might underlie the associations of insomnia and sleep quality with pain and somatic symptoms. (C) 2011 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.