Danish twin study estimates genetic contribution to rotator cuff tears

Researchers linked the Danish Twin Registry with the Danish National Patient Registry in a nationwide population-based study of monozygotic and dizygotic twins born from 1940 to 1980. Rotator cuff tear diagnoses recorded between 1994 and 2014 were identified using ICD-8 and ICD-10 codes. The investigators estimated cumulative incidence, compared casewise concordance in twins, and used biometric models to assess genetic and environmental contributions to liability.

By age 70, cumulative incidence of a recorded rotator cuff tear diagnosis was 6.5% in men (95% CI, 6.0%–7.2%) and 3.8% in women (95% CI, 3.4%–4.3%). A twin’s risk was generally higher when their co-twin had a diagnosis, with stronger aggregation in monozygotic than dizygotic pairs, particularly among men. In the full cohort, the preferred model estimated that additive genetic effects accounted for 49% of liability (95% CI, 27%–70%) and unique environmental effects for 51% (95% CI, 30%–73%).

The findings suggest that genetic factors contribute to susceptibility, alongside environmental influences. Estimates among women were less precise. Because cases were identified through registry diagnoses, the study describes clinically recorded tears and does not establish how genetic information should alter prevention or clinical management.