To investigate the risk of total hip replacement (THR) due to primary osteoarthritis in relation to cumulative occupational mechanical exposures and lifestyle factors.


Using register information, we identified first-time THR cases within the Danish working population in 2005–2006. For each case, 2 age- and sex-matched controls were drawn. Persons within 2,500 randomly selected case–control sets received a questionnaire about job history, weight at age 25 years, present weight and height, smoking, and sports activities at age 25 years. The job history was combined with a job exposure matrix. Cumulative exposure estimates were expressed according to the pack-year concept of smoking (e.g., cumulative lifting was expressed as ton-years). We used conditional logistic regression for statistical analyses.


In total, 1,776 case–control sets (71%) were available for analysis. The adjusted odds ratio (OR) for exposure to ≥20 ton-years was 1.35 (95% confidence interval [95% CI] 1.05–1.74) for men and 1.00 (95% CI 0.73–1.41) for women. Standing/walking and whole body vibration showed no associations. The adjusted OR for body mass index (BMI) ≥30 kg/m2 at age 25 years was 2.44 (95% CI 1.38–4.32) for men and 5.12 (95% CI 2.30–11.39) for women. The corresponding adjusted ORs for an increase in BMI of ≥10 kg/m2 since age 25 years were 2.16 (95% CI 1.25–3.70) and 2.46 (95% CI 1.47–4.13). Sports participation showed weak positive associations, while pack-years of smoking showed no associations.


The results indicated a modest increase in risk of THR in relation to cumulative lifting among men and an increased risk in relation to a high BMI at age 25 years and to a gain in BMI in both sexes.