How Many Hemophilia Patients Are There?

Written by: David Clark, PhD, chair of the Coalition for Hemophilia B

A 2019 study(1) suggested that there could be up to three times more hemophilia patients than originally estimated. Following up on that study, a group of researchers(2) studied the prevalence of hemophilia in the United States. Using data on the number of patients seen at Hemophilia Treatment Centers (HTCs) between 2012 and 2018 — adjusted to account for the percentage of hemophilia patients who use HTCs (67–80%) — they estimate that there are approximately 29,761 to 32,985 males with hemophilia in the United States, of which 76.5% had hemophilia A and 23.5% were Bs.  

This gives an estimated population of 6,994 to 7,751 males with hemophilia B in the United States. They estimate that the incidence of hemophilia B is 1 in 19,283 live male births.

INCIDENCE AND PREVALENCE ARE TWO DIFFERENT MEASURES

When we ask how many people currently living have hemophilia, we’re talking about prevalence.  Prevalence always refers to a time period. We could ask how many people have hemophilia now, or sometime in the past. For hemophilia, prevalence refers to the number of people with hemophilia compared to the total number of people in the population being studied.

As far as we know, the incidence of hemophilia is the same regardless of race or ethnicity. The difference comes from the risk of death for the group. Blacks and Hispanics tend to live shorter lives than whites in the U.S., so they don’t contribute as much to the overall prevalence as whites.

Incidence is how often something happens. Hemophilia only happens to a person once, so for hemophilia the incidence is equal to the number of births of people with hemophilia compared to the total number of births in the population being studied. If everyone lived exactly the same lifespan, the incidence and prevalence of hemophilia would be equal. Since lifespans vary, they are different.

One thing the researchers did was to calculate the prevalence for different racial and ethnic groups. They found a higher prevalence of hemophilia among whites (15.1 per 100,000 males) than among Blacks and Hispanics (both were 12.4 per 100,000 males). At first, Blacks and Hispanics appear to have an advantage, but that’s not actually true. As far as we know, the incidence of hemophilia is the same regardless of race or ethnicity. That is, everyone has the same chance of being born with hemophilia. The difference comes from the risk of death for the group. Blacks and Hispanics tend to live shorter lives than whites in the United States. Therefore, they don’t contribute as much to the overall prevalence as whites.

This is the latest estimate for the U.S. only. The actual number is unknown because we do not have good data on how many women have hemophilia.

Note that the study also did not compile data on women with hemophilia. That is probably much more difficult since many female hemophilia patients have trouble receiving treatment and therefore are unknown to the system. Including females could significantly increase the numbers. It has been estimated that for every male with hemophilia there are 4 to 5 associated female carriers, sisters, mothers, aunts, etc. We don’t know how many of them will actually have hemophilia, but it could be a substantial number that could more than double the overall estimate.

REFERENCES

1. A. Lorio et al., Annals of Internal Medicine, 171(8): 540-546, 2019.
2. J. M. Soucie et al., Haemophilia, 26(3): 487-493, 2020.