A paper published in BMJ Open, “Male pattern baldness and its association with coronary heart disease: a meta-analysis,” drew lots of news coverage.
When I began to scan some of the news, I scratched my head, pulled out some hair, tousled what was left, and finally decided I had to address some of what I saw. Around the world I saw headlines such as:
Each was technically wrong, for reasons I’ll explain in a moment.
The stuff on the NBC News website bothered me the most. Both the online and the on-air NBC versions.
On-the-air, Dr. Nancy Snyderman got caught in a jumbled confusion of terminology, reporting:
“The report concludes there is likely an association between hair loss and heart disease.”
“Likely” is a misplaced qualifier. The report DID conclude there was an association. A statistical association. That’s all that an observational study like this can conclude.
But then Dr. Snyderman continued:
“it’s this type of male baldness that is getting the attention. the hair loss starts on the crown of the head and slowly spreads. the men in this category showed the highest risk of heart disease. And the bigger that bald spot, the higher the risk.”
Now that’s where I think a qualifier was needed. An observational study like this can’t prove cause and effect, so it can’t establish “risk” of heart disease being caused. It can only point to a statistical association, which required none of the hedging that was supplied. But we think it’s important to always include an explanation of the conclusions you may not be able to draw from an observational study. Association/correlation ≠ causation.
Instead, the NBC News story profiled a man who “was barely out of his teens when he started losing his hair” and who is now 59 with heart disease. They quoted him saying, “Had I known then what I know now I probably would have been more vigilant.” This anecdote strongly suggests or the supports the notion of cause-and-effect, which has simply not been established.
The online version was more troublesome. It stated:
“The findings suggest that men who are losing their hair should head over to the doctor’s office and get a check-up.”
The findings don’t suggest that to me at all.
And they didn’t suggest that to USA Today, either, which had a prominent sub-heading: “No need to rush to the doctor’s office.”
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