Relationships Between Chronic Musculoskeletal Pain and Working Hours and Sleeping Hours: A Cross-sectional Study.

Ten to twenty percent of the population of Japan has chronic pain. Although studies have confirmed a relationship between sleeping hours and chronic pain, it remains unclear whether there is an association between working hours and chronic pain, especially chronic musculoskeletal pain (CMP), in workers. A self-administered questionnaire that sought information regarding background characteristics and work-related factors was sent to 118 enterprises; finally, 1,747 participants were included in the analysis and were classified into CMP (n = 448) and non-CMP (n = 1299) groups. Logistic regression analysis revealed that age (odds ratio [OR] = 1.02, 95% confidence interval [CI]: 1.01-1.03), sex (reference: female, OR = 0.68, 95% CI: 0.52-0.88), working hours (OR = 1.11, 95% CI: 1.03-1.20), and sleeping hours (OR = 0.84, 95% CI: 0.75-0.95) were significantly associated with CMP. Participants were categorized into four groups according to working hours (long: ≥ 9 hours/day [long-work], short: < 9 hours/day [short-work]) and sleeping hours (long: ≥ 7 hours/day [long-sleep], short: < 7 hours/day [short-sleep]). Furthermore, logistic regression analysis showed that the CMP OR was 2.02 (95% CI: 1.46-2.78) times higher in 'long-work plus short-sleep workers' and 1.47 (95% CI: 0.94-2.30) times higher in 'long-work plus long-sleep workers' than in 'short-work plus long-sleep workers'. Thus, working hours are associated with CMP frequency, but sleeping sufficiently may prevent CMP in workers even if they work for long hours. In conclusion, adequate instructions on sleeping hours should be provided by occupational health staff, as this may be effective in preventing CMP.