Day-to-day association of night work with musculoskeletal pain and other symptoms: results from the 1001 nights-cohort.

Objectives: Night work disrupts sleep, which may increase inflammatory processes, pain sensitivity and pain perception. We investigated effects of night shifts on musculoskeletal pain (MSP) and other mental and somatic symptoms using day-to-day measurements in a within-person design. We also disentangled the effect of night work from the effects of shift-related differences in job demands and sleep.

Methods: We included 522 hospital employees with data on ≥1 day shift (n=1926) and ≥1 night shift (n=1422). Participants reported their working hours, MSP, other mental and somatic symptoms, sleep and psychosocial and physical job demands daily for 14 days. We estimated prevalence ratios (PRs) of MSP and symptoms when working night shifts compared with day shifts.

Results: After adjusting for age and job demands, night shifts were associated with pain in the lower extremities (PR 1.12; 95% CI 1.01 to 1.25), gastrointestinal symptoms (PR 2.12; 95% CI 1.26 to 3.53) and other mental and somatic symptoms (PR 2.54; 95% CI 1.31 to 4.91). Adjustment for sleep duration did not alter these findings. However, longer shift duration may explain the higher occurrence of lower extremity pain during night shifts.

Conclusions: We found no evidence of a general effect of night work on MSP. Only an acute effect on lower extremity pain was observed, which may be attributable to longer night shift duration. Employees also more frequently reported other types of symptoms when working night shifts, even after adjusting for job demands and sleep duration. Thus, physiological effects related to circadian misalignment may be a plausible explanation.