Previous studies have revealed that hormone therapy raises cardiovascular risk.
- a 41 percent higher risk of stroke
- a 29 percent higher risk of a heart attack
- a 100 percent higher risk of blood clots
Estrogen alone increases stroke risk by 39 percent and blood clot risk by 47 percent, according to the same NIH estimates.
However, how does hormone therapy affect people who are gender transitioning? So far, scientists have not addressed this question fully, so a new study aimed to fill this gap in research.
Dr. Nienke Nota — a researcher in the Department of Endocrinology at the Amsterdam University Medical Center in the Netherlands — and her team examined the medical records of 3,875 Dutch transgender people who had hormone therapy between 1972 and 2015.
Trans women twice as likely to have a stroke
Their study examined 2,517 transgender women and 1,358 transgender men. The women were 30 years old, on average, and they had received estrogen either alone or in combination with androgen suppressors.
The men were 23 years old, on average, and they received testosterone therapy as a part of their gender transition.
Dr. Nota and her colleagues clinically followed the trans women for an average period of 9 years and the trans men for an average of 8 years after they started hormone therapy.
The researchers examined the incidence of cardiovascular problems such as heart attacks, strokes, and blood clots among transgender people and compared it with the incidence of such events in cis men and cis women.
Cis people are those whose gender identity matches the biological sex assigned to them at birth.
The study found that trans women were more than twice as likely to have a stroke as cis women and almost twice as likely to have a stroke as cis men.
Trans women were also five times and 4.5 times more likely to develop blood clots than cis women and cis men, respectively.
Trans women also had heart attacks more than twice as often as cis women, and trans men were over three times more likely to have a heart attack than cis women.
Dr. Nota comments on the findings, saying, "In light of our results, we urge both physicians and transgender individuals to be aware of this increased cardiovascular risk."
"It may be helpful to reduce risk factors by stopping smoking, exercising, eating a health[ful] diet and losing weight, if needed before starting therapy, and clinicians should continue to evaluate patients on an ongoing basis thereafter."
Dr. Nienke Nota
The authors caution that their analysis did not account for modifiable risk factors such as smoking, stress, diet, and exercise.
However, they say that hormone therapy may be largely to blame for the increased cardiovascular risk.
Specifically, estrogen promotes blood clotting, and testosterone could do the same by raising the concentration of red blood cells and increasing the levels of bad cholesterol, they explain.