One in five doctors in Sweden has a parent who is also trained in medicine, more than triple the proportion for doctors born three decades earlier, finds a study in the Christmas issue of The BMJ.

The findings suggest that among doctors in Sweden, medicine might increasingly run in families.

Parents’ occupations might influence the career choice of their children, through information, opportunities, and economic means. If a large or growing proportion of doctors are from families of medical professionals, the diversity of the healthcare workforce might be limited, and growing evidence suggests that this might affect patient outcomes.

However, the extent to which medicine runs in families is unknown.

To address this knowledge gap, a team of US researchers explored data from Swedish educational records spanning up to three generations to see whether doctors had relatives that also trained as medical professionals.

They analyzed how the proportion of doctors with at least one parent also trained in medicine changed over time. The study included 47,400 people with a medical degree, born in 1950-1990, and living in Sweden at some point during 2001-2016.

They also analyzed lawyers and their families to see if the pattern would also hold true for another high paying occupation.

Among 27,788 doctors, where the educational background for both parents was known, 14% had a parent who was also a doctor and 2% had two doctor parents.

The proportion of doctors with at least one doctor parent rose significantly over time, from 6% for doctors born in 1950-59 to 20% for those born in 1980-90.

A similar pattern was not seen in lawyers.

Of 29,066 doctors with at least one sibling whose educational background was known, 14% had a sibling who was also a doctor. And among 18,360 doctors with at least one aunt or uncle whose educational background was available, 9% had an aunt or uncle who was a doctor.

For 18,061 doctors with at least one grandparent whose educational background was known, 2% had at least one grandparent with a medical degree.

Except for siblings, the proportions of doctors with these more distant relatives who were also trained in medicine increased over time.

This is an observational study, and so can’t establish cause. The authors also point to some limitations, including that they only studied a single country and data were missing on parental education for some doctors born outside of Sweden.

But they say that their findings are consistent with older, smaller studies that have reported similar proportions of medical students with a doctor parent.

“Our analysis showed an increasing number of physicians from families with other physicians, rather than an increasing proportion of physicians from families with more diverse economic and educational backgrounds,” they write.

“Uncovering the exact mechanism that underlies our findings is important for future research”, they conclude.