0140 Risk of total hip replacement in relationship to cumulative exposures in the work environment

Objectives To investigate the risk of total hip replacement (THR) due to primary osteoarthritis (OA) in relation to cumulative occupational mechanical exposures and lifestyle factors. Method In a population of Danish employees, we identified first-time THR cases in the National Patient Register. For each case, two age- and sex-matched controls were drawn. In total 2500 randomly selected case-control sets were mailed a questionnaire entailing job history, weight (present and at age 25), height, smoking and sports activities at age 25. We used a job exposure matrix to calculate cumulative exposures in the work environment. Exposure estimates were expressed according to the pack-year concept of smoking (cumulative lifting = ton-years). We used conditional logistic regression. Results 71% of case-control sets contributed to the study. The adjusted odds ratio for exposure to at least 20 ton-years was 1.35 (95% CI 1.05–1.74) for men. When analysing frequent lifting as risk factor, the adjusted OR reached 1.26 (95% CI 0.99–1.61). There were no such increases for women. We controlled for body mass index, sports participation at age 25 and previous trauma towards the knees. Conclusions When using a job exposure matrix we found a modest increased risk of THR in relation to cumulative lifting for men. For women no increased risk was seen.