A total of 5,599 twins had complete data on AD at both time points. From the first to the second wave, 10 subjects had new onsets of LTH-AD. As our aim was to use 2 measurement points to assess the disorder during the same life period, these cases were removed from further analyses (see below). The final sample for this study thus comprised 5,589 subjects, including 4,203 men and 1,386 women. The women in the sample were from opposite sex dizygotic (DZ) pairs and could therefore not be analyzed in twin modeling. Only 4,203 men were therefore retained for further analyses. The twin pairs comprised 693 monozygotic (MZ) pairs, 477 DZ pairs, and 231 individuals without their co-twin.
