Transgender individuals receiving hormone therapy may have a greater risk of cardiovascular events such as stroke, venous thromboembolism, and myocardial infarction when compared with the general population, according to a study that analyzed medical records of more than 6,000 patients.

“In light of our results, we urge both physicians and transgender individuals to be aware of this increased cardiovascular risk,” first author Nienke M. Nota, MD, said in a press release for the study, which was published online Feb. 18 in Circulation. “It may be helpful to reduce risk factors by stopping smoking, exercising, eating a healthy diet, and losing weight, if needed, before starting therapy, and clinicians should continue to evaluate patients on an ongoing basis thereafter.”Dr. Nota and her colleagues at the Amsterdam University Medical Center analyzed the risk of cardiovascular events by comparing the medical records of 6,793 individuals, including only patients who received hormone therapy at their center or affiliate. They did not include those who had discontinued hormone therapy for an extended period or had alternated female and male sex hormones.

They defined transmen as indiviuals assigned female sex at birth but who had male gender identity, and transwomen as those assigned male sex at birth but with female gender identity.*

Researchers analyzed 2,517 transwomen (median age 30 years) and 1,358 transmen (median age 23 years) who received hormone therapy (defined as estrogen with and without androgen-suppressors for transwomen and testosterone for transmen) at the center gender’s clinic between 1972 and 2015. These records were compared with those of cisgender women and men (individuals whose gender identity matches their assigned birth gender).

The mean follow-up duration was 9.07 years for transwomen and 8.10 years for transmen. The researchers compared observed cases of stroke, myocardial infarction (MI), and venous thromboembolism (VTE) with expected cases using cisgender reference women and men. There were 29 stroke events, 30 MIs, and 73 VTE events for transwomen and 6 stroke, 11 MIs, and 2 VTE events for transmen.

There was a greater risk of stroke for transwomen, compared with cisgender women (standardized incidence ratio [SIR] = 2.42) and cisgender men (1.80), and a significantly greater risk of VTE, compared with cisgender women (5.52) and cisgender men (4.55).

The rate of MI was also significantly higher in transwomen, compared with cisgender women (2.64) and in transmen compared with cisgender women (3.69).

In a subgroup analysis, the researchers found ethinylestradiol use prior to 2001 did not significantly change the incident rate of cardiovascular events, but noted there was a lower rate of VTE when transwomen who began hormone therapy prior to 2001 were excluded from the analysis.

The researchers noted that hormone therapy may increase the risk of cardiovascular events in transgender individuals, in part, due to hormone therapy’s effect on cardiovascular risk factors such as lipid levels. Although a previous study analyzed the risk of cardiovascular events in transwomen and transmen, the researchers said that study could not conclude there was an increased risk of cardiovascular events for transmen.

The researchers said the results may be limited by study design, and their analysis of medical records could not account for potential confounders such as psychosocial stressors and smoking, as well as the decreasing risk of cardiovascular events over the period of the study, and assessing cardiovascular events differently than reference studies used.

The study had no specific funding, and the authors reported no relevant conflicts of interest.

SOURCE: Nota NM et al. Circulation. 2019 Feb 18. doi: 10.1161/CIRCULATIONAHA.118.038584

*Correction 2/25/2019: An earlier version of this story incorrectly defined transwomen and transmen. The definitions are now accurate.