Figure 1. Identification of 3759 Transgender Individuals in a Cohort of 6 657 456 Danish-Born Individuals Aged 15 Years or Older Who Resided in Denmark for at Least 1 Day Between January 1, 1980, and December 31, 2021.

ICD indicates International Classification of Diseases; PID, personal identifier.

^aLegal change of gender was identified as 2 separate records in the Civil Registration System, in which the first record indicated the date until which the sex assigned at birth was considered valid and the second record indicated the date when the legal change of gender took place.

^bThe 10-digit PID was introduced in 1968 and there were multiple corrections to the Civil Registration System in subsequent years, suggestive of error corrections rather than legal change of gender. For this reason, PID corrections made before 1977 were disregarded.

^cIndividuals for whom the legal change of gender was not recorded as taking place on 2 consecutive dates were excluded.