duration/type of hormone therapy use. We included dummy variables for missing covariate data, which comprised less than 5% of total person-time (except for missing breastfeeding which was 9.5%). Tests for trend were calculated using alcohol consumption as a continuous variable. Tests for interaction were performed using the Wald test for the cross-product interaction term. The proportional hazards assumption was not violated. All analyses were performed using SAS software, version 9.1 with a two-sided significance p-value <0.05.
