Potential Risk Factors of Persistent Low Back Pain Developing from Mild Low Back Pain in Urban Japanese Workers

STUDY DESIGN Two-year, prospective cohort data from the Japan epidemiological research of occupation-related back pain study in urban settings were used for this analysis. OBJECTIVE To examine the association between aggravated low back pain and psychosocial factors among Japanese workers with mild low back pain. SUMMARY OF BACKGROUND DATA Although psychosocial factors are strongly indicated as yellow flags of low back pain (LBP) leading to disability, the association between aggravated LBP and psychosocial factors has not been well assessed in Japanese workers. METHODS At baseline, 5,310 participants responded to a self-administered questionnaire including questions about individual characteristics, ergonomic work demands, and work-related psychosocial factors (response rate: 86.5%), with 3,811 respondents completing the 1-year follow-up questionnaire. The target outcome was aggravation of mild LBP into persistent LBP during the follow-up period. Incidence was calculated for the participants with mild LBP during the past year at baseline. Logistic regression was used to explore risk factors associated with persistent LBP. RESULTS Of 1,675 participants who had mild LBP during the preceding year, 43 (2.6%) developed persistent LBP during the follow-up year. Multivariate analyses adjusted for individual factors and an ergonomic factor found statistically significant or almost significant associations of the following psychosocial factors with persistent LBP: interpersonal stress at work [adjusted odds ratio (OR): 1.96 and 95% confidence interval (95%CI): 1.00-3.82], job satisfaction (OR: 2.34, 95%CI: 1.21-4.54), depression (OR: 1.92, 95%CI: 1.00-3.69), somatic symptoms (OR: 2.78, 95%CI: 1.44-5.40), support from supervisors (OR: 2.01, 95%CI: 1.05-3.85), previous sick-leave due to LBP (OR: 1.94, 95%CI: 0.98-3.86) and family history of LBP with disability (OR: 1.98, 95%CI: 1.04-3.78). CONCLUSIONS Psychosocial factors are important risk factors for persistent LBP in urban Japanese workers. It may be necessary to take psychosocial factors into account, along with physical work demands, to reduce LBP related disability.