Cumulative occupational shoulder exposures and surgery for subacromial impingement syndrome: a nationwide Danish cohort study
Objectives The primary aim was to examine exposure–response relationships between cumulative occupational shoulder exposures and surgery for subacromial impingement syndrome (SIS), and to compare sex-specific exposure–response relationships. The secondary aim was to examine the time window of relevant exposures.
Methods We conducted a nationwide register study of all persons born in Denmark (1933–1977), who had at least 5 years of full-time employment. In the follow-up period (2003–2008), we identified first-time events of surgery for SIS. Cumulative exposure estimates for a 10-year exposure time window with a 1-year lag time were obtained by linking occupational codes with a job exposure matrix. The exposure estimates were expressed as, for example, arm-elevation-years in accordance with the pack-year concept of tobacco consumption. We used a multivariable logistic regression technique equivalent to discrete survival analysis.
Results The adjusted OR (ORadj) increased to a maximum of 2.1 for arm-elevation-years, repetition-years and force-years, and to 1.5 for hand-arm-vibration-years. Sex-specific exposure–response relationships were similar for men and women, when assessed using a relative risk scale. The ORadj increased gradually with the number of years contributing to the cumulative exposure estimates. The excess fraction was 24%.
Conclusions Cumulative occupational shoulder exposures carried an increase in risk of surgery for SIS with similar exposure–response curves for men and women. The risk of surgery for SIS increased gradually, when the period of exposure assessment was extended. In the general working population, a substantial fraction of all first-time operations for SIS could be related to occupational exposures.