In the first analysis, we used Cox proportional hazards models to investigate the risk for death from age 15 years until death (7.2%), emigration (4.6%), or follow-up until 2010 (88.2%) in individuals as a function of their first AUD registration. As the first registration for AUD could occur at varying ages, we treated AUD as a time-dependent covariate17: ie, from age 15 years until year of the first AUD registration, individuals were treated as AUD free, while from that AUD registration, they were considered registered for AUD. In the model, the proportionality assumption—that the hazard ratios (HRs) were constant over time—was not fulfilled because the AUD-mortality association varied across ages. Therefore, we allowed the effect of AUD to differ based on age intervals. We tested several different models and selected our model based on fit values (lowest Akaike Information Criterion [AIC]18) and nonoverlapping 95% CIs for the effect of AUD. In the final model, we included the following age intervals: 15 to 24, 25 to 29, 30 to 39, 40 to 44, 45 to 49, 50 to 54, 55 to
