Objectives Little is known about the time window for accumulation of occupational exposures and shoulder disorders. We aimed to evaluate cumulative occupational shoulder exposures as risk factors for surgery for subacromial impingement syndrome (SIS), and to examine how long the relevant exposure time period is.

Method We conducted a nationwide register study of all persons born in Denmark (1933–1977), with at least 5 years of full-time employment (1993–2007). In the follow-up period (2003–2008), first-time events of surgery for SIS were identified. Cumulative exposure estimates for a 10-year period were obtained by linking occupational codes with a job exposure matrix. Exposure estimates were expressed according to the pack-year concept of smoking (e.g. arm-elevation-years). We used logistic regression equivalent to discrete survival analysis with a one year time lag, adjusting for age, sex, region, and calendar year, and compared the ORs for exposure time windows of increasing length.

Results The adjusted OR (ORadjusted) for surgery for SIS reached 2.0 for arm-elevation-years, repetitive-movement-years, and force-years, and the ORadjusted for hand-arm-vibration-years reached 1.5. We found an increase in ORadjusted from 1.0 to 2.1 when expanding the exposure time window from 2 to 10 years back in time.

Conclusions Our findings suggested that upper arm-elevation, repetitive movements, forceful exertions, and hand-arm-vibration were risk factors for surgery for SIS, and indicated a cumulative exposure effect within a 10 year time span.