Down syndrome and the upper class: the data nobody can provide

Why Down syndrome is not more common in wealthy families

Down syndrome does not care about surnames. It cares, above all, about ages. The claim that trisomy 21 clusters among executives and well-off families circulates with confidence, but Spain has no public register to support it —nor, it should be said, one that refutes it with surgical precision—. What is documented is something else: incidence depends fundamentally on the mother's age at conception, not on the balance of a bank account.

Endogamy, Opus Dei and a textbook confusion

Trisomy 21 is, in the vast majority of cases, a chromosomal sorting error that occurs in the reproductive cell, with no family history behind it. Consanguinity does not cause it. Inbreeding multiplies the risk of recessive diseases, and there is indeed a textbook case: the haemophilia Queen Victoria spread across half of Europe, which left its mark on the descendants of several royal houses. That is the real phenomenon the argument borrows to talk about something it does not apply to.

Where the argument touches verifiable ground is at the other end of the process: whether a prenatal diagnosis ends in a voluntary termination of pregnancy. There, religious affiliation, access to screening tests and the family environment all matter. That alters the births counted, not the conceptions. And it helps explain why the social composition of births with Down syndrome can vary without the biology changing.

The missing data

An incidence ten or fifteen times higher is cited, that 90% of cases would be in that group, and the profile of executives with two or three children where one is born with Down syndrome. None of those figures is backed by a national register of congenital anomalies broken down by income. Without that breakdown, the conversation rests on anecdotes, which is the material from which both class prejudice and family legends are built.

As long as that register does not exist —and nothing suggests it will be created any time soon—, the figure will keep circulating in both directions, each side with its favourite example. The likely outcome is that the discussion stays where it is: in perception, which is the ground where data nobody has measured grows best.