Mediating impact of sleep quality and duration on the relationship between socio-economic conditions and pain

BACKGROUND: Sleep-related problems exhibit strong social patterning and are associated with pain; however, their mediating role in socio-economic inequities in pain remains largely unknown. We aim to assess the extent to which life course socio-economic inequities in pain experience and severity are mediated through sleep quality and duration. METHODS: We used data from 1719 individuals [52.0% women; mean age 60.1 years (SD 9.1)] from the Swiss CoLaus|PsyCoLaus study, with both sleep measures at baseline (2009-2012) and pain measures at follow-up (2014-2017). Life course socio-economic conditions were assessed by using the father's and individual's occupational position, educational level, and income. Potential mediators included self-reported sleep quality (measured by using the Pittsburgh Sleep Quality Index, ranging from 0 to 21, with high scores indicating poorer sleep quality) and duration (short <6 h/night; normal 6-8.5 h/night; long >8.5 h/night). Presence of pain, chronic pain, and pain severity were assessed by using a self-administered questionnaire. We estimated age, sex, and country of birth with adjusted β coefficient, odds ratio, and proportion mediated by using counterfactual mediation analyses. RESULTS: Pain and chronic pain were reported by 47% and 40.8% of the participants, respectively. Among 699 participants with reported pain severity data, the mean pain severity score was 3.6 (SD 1.7) (scale ranging from 0 = no to 10 = worst imaginable pain). Sleep quality explained 30% of the educational, 21% of the occupational, and 45% of the income inequities in pain; 20% of the occupation and 51% of the income inequities in chronic pain; and 15%, 9%, and 16% of the father's occupation, educational, and income inequities in pain severity, respectively. Short sleep duration explained 31% of the education inequities in pain and 37% of the education and income inequities in chronic pain. CONCLUSION: This study suggests poor sleep quality and short sleep duration partially mediate socio-economic inequities in pain. The role of other potential mediators at individual and societal levels should be further investigated.