We assessed the degree to which the results from the regression model reflected familial confounding using a co-relative design. With the Swedish Multi-Generation Register and the Swedish Twin Register, we identified all monozygotic (MZ) twin pairs and full- and half-sibling pairs. Using stratified Cox proportional hazards models, we refit all analyses within strata of specific relative set(MZ twins: 5507 total pairs, with 532 AUD discordant; full-siblings: 781 608 sibships, with 100 128 containing members discordant for AUD; and half-siblings: 291 520 total pairs, with 54 416 AUD discordant). Only sets where members differed in exposure to AUD at some age contributed to regression results. Within each strata, the HR was then adjusted for the familial cluster, and, therefore, accounts for an array of unmeasured genetic and environmental factors shared by relatives.
