Objective To identify potential risk factors for the development of new-onset sciatica in initially symptom-free Japanese workers with no history of sciatica.

Methods Two-year, prospective cohort data collected for the Japan Epidemiological Research of Occupation-related back pain (JOB) study were used for the analysis. In total, 5,310 participants responded to a self-administered baseline questionnaire (response rate: 86.5%). Furthermore, 3,194 (60.2%) completed both 1- and 2-year follow-up questionnaires. The baseline questionnaire assessed individual characteristics, ergonomic work demands, and work-related psychosocial factors. The outcome of interest was new-onset sciatica with or without low back pain (LBP) during the 2-year follow-up period. Incidence was calculated for participants who reported no history of lumbar radicular pain (sciatica) and no LBP in the past year prior to baseline. Logistical regression assessed risk factors associated with new-onset sciatica.

Results Of 765 eligible participants, 141 (18.4%) reported a new episode of sciatica during the 2-year follow-up. In crude analysis, significant associations were found between new-onset sciatica and age and obesity. In adjusted analysis, significant associations were found for obesity and mental workload in a qualitative aspect after controlling for age and gender. Consequently, in multivariate analysis with all the potential risk factors, obesity remained statistically significant (OR: 1.80; 95% CI: 1.19–2.71) while age (≥ 50 years vs. < 40 years) was almost significant (OR: 1.55, 95% CI: 0.99–2.44).

Conclusions In previously asymptomatic Japanese workers, the risk of developing new-onset sciatica is mediated by individual factors such as age and obesity. Our findings suggest that the management of obesity may prevent new-onset sciatica.