Cohort study of occupational risk factors of low back pain in constructionworkers

Objectives-To identify work related risk factors of future low back pain (L BP) in a cohort of construction workers free of LBP at the start of follow up. Methods-The Hamburg construction worker study comprises 571 male constructi on workers who have undergone two comprehensive interview and physical exam ination surveys. A cohort of 285 subjects without LBP at baseline was ident ified. After a follow up of 3 years, the 1 year prevalence of self reported LBP was determined in the 230 men followed up (80.7%). Prevalence ratios ( PRs) with 95% confidence intervals (95% CIs) of LBP at follow up according to self reported work tasks of construction workers measured at baseline we re estimated from Cox's regression models which were adjusted for age, and anthropometric measures. Results-At follow up 71 out of 230 workers (30.9%) reported LBP during the preceding 12 months. Four work tasks (scaffolding, erecting roof structures , sawing wood, laying large sandstones) with an increased risk of 1 year pr evalence of LBP at follow up were further evaluated. After further adjustme nt for occupation the relative risk was increased for workers who had repor ted greater than or equal to 2 hour/shifts laying large sandstones (PR=2.6; 95% CI 1.1 to 6.5). Work load of bricklayers was additionally estimated by an index on stone load (high exposure: PR=4.0; 95% CI 0.8 to 19.8), and an index for laying huge bricks/blocks (yes/no: PR=1.7; 95% CI 0.5 to 5.7). Conclusions-The results suggest that self reported differences in brick cha racteristics (size and type of stone) and temporal aspects of the work of b ricklayers (average hours per shift laying specified stones) can predict th e future prevalence of LBP. The data have to be interpreted with caution be cause multiple risk factors were tested.