Objectives To estimate the risk of surgery for subacromial impingement syndrome (SIS) in relation to occupational exposures, lifestyle factors and diabetes mellitus.

Methods We conducted a case–control study nested in a register-based cohort study of the Danish working population. For each of 3000 first-time cases of surgery for SIS, two age-matched and sex-matched controls were drawn. Cases and controls received a questionnaire on job history and other factors. Job histories were combined with a psychosocial job exposure matrix (JEM) and the updated Shoulder JEM, which provided exposure intensities on measurement scales. Ten-year cumulative exposures to upper arm elevation >90°, repetitive shoulder movements, forceful shoulder exertions and hand–arm vibrations (HAVs) were estimated. We used conditional logistic regression.

Results There were 5396 persons (60%) who answered the questionnaire. For occupational mechanical exposures, the adjusted OR (OR_adj) ranged from 1.9 (95% CI 1.5 to 2.5 for HAVs) to 2.5 (95% CI 1.9 to 3.5 for force) among men and 1.7 (95% CI 1.2 to 2.5 for HAVs) to 2.0 (95% CI 1.3 to 2.9 for force) among women. No statistically significant associations were found for occupational psychosocial factors. Body mass index (BMI) and pack-years of smoking showed OR_adj up to 2.0. Diabetes mellitus showed OR_adj of 1.5 (95% CI 1.1 to 2.2) for men and 2.2 (95% CI 1.4 to 3.4) for women.

Conclusions Our findings add to the evidence of an increased risk of surgery for SIS in relation to occupational cumulative mechanical exposures, even when an increased risk in relation to BMI, smoking and diabetes mellitus is taken into account.