Cardiovascular risk in Danish transgender persons: a matched historical cohort study

Background: Cardiovascular risk could be increased in transgender persons, but the mechanism is undetermined. Aim: The aim of this study was to assess the risk of cardiovascular outcomes in Danish transgender persons compared to controls. Methods: The study design was a historical register-based cohort study in Danish transgenders and age-matched controls. The main outcome measure was cardiovascular diagnosis (any CVD) including medicine prescriptions for CVD during 2000-2018. The transgender cohort (n = 2671) included persons with International Classification of Diseases-10 diagnosis code of 'gender identity disorder' (n = 1583) and persons with legal sex change (n = 1088), 1270 were assigned female at birth (AFAB) and 1401 were assigned male at birth (AMAB). Controls (n = 26 710) were matched by age (n = 5 controls of same and n = 5 controls of other birth sex) of the respective transgender. Results: The median (interquartile range) age at study inclusion was 22 (18; 29) years for AFAB and 26 (21; 39) years for AMAB. The mean (s.d.) follow-up time was 4.5 (4.2) years for AFAB and 5.7 (4.8) years for AMAB. The hazard ratio (HR) for any CVD was significantly higher in transgenders vs controls of same and other birth sex, with highest adjusted HR in transgenders AFAB vs control men: 2.20 (95% CI: 1.64;2.95), P < 0.001. Gender-affirming hormone treatment (GAHT) explained part of elevated risk of CVD in transgenders AFAB, whereas GAHT did not contribute to the elevated risk of CVD in transgenders AMAB. Conclusions: The risk of cardiovascular diagnosis was increased in transgenders. The mechanism should be further investigated.