Aims This study examines the impact of work-related psychosocial and mechanical exposure on the development of low back pain (LBP) in the general working population.

Methods A randomly drawn cohort from the general population in Norway aged 18–66 years was followed up for 3 years (n=12 550, response rate at baseline=67%). Eligible respondents were in paid work during a reference week in 2006 and 2009, or temporarily absent from such work (n=6745). Five work-related psychosocial factors and seven mechanical exposures were measured. Outcomes of interest were moderate or severe LBP at follow-up adjusted for baseline LBP.

Results In total, 12.8% (861 individuals) reported LBP during the last month at follow-up. Work-related psychosocial predictors of LBP were high job demands (OR 1.41, 95% CI 1.16 to 1.72) and low job control (OR 1.26, 95% CI 1.01 to 1.57). Mechanical factors were prolonged standing (OR 1.48, 95% CI 1.20 to 1.83), awkward lifting (OR 1.55, 95% CI 1.28 to 1.88) and squatting/kneeling (OR 1.29, 95% CI 1.04 to 1.61). The estimated population risk attributable to these factors was approximately 42%. The risk for LBP associated with psychosocial exposure was not influenced by adjustment for mechanical risk factors, and vice versa. There was no substantial confounding related to age, gender, education, occupation or psychological distress.

Conclusions Highly demanding jobs, prolonged standing and awkward lifting appear as the most consistent and important predictors of LBP.