Friday, April 18, 2014

Correlation or Causation?

To summarize, back in the 80s and 90s, because scientists had noted a correlation between estrogen replacement therapy and a decreased risk of heart disease, many women were put on estrogen replacement by their doctors.
Twenty years later, a controlled randomized study showed that in fact, estrogen replacement was very bad for heart disease! Oops.
How could a mistake of this magnitude occur?
It turned out that women of higher socioeconomic status who were more interested in their health (or better positioned to do something about it) were much more likely to ask for or agree to take estrogen than poorer women who had less access to health care.
And while on the surface it may have looked as if hormone replacement therapy reduced a woman’s risk of heart disease, in fact, it was a woman’s socioeconomic class that actually predicted that risk.
Middle and upper class women were less likely to suffer from heart disease – despite the fact that more of them were on hormone replacement therapy, not because they were on hormone replacement therapy.
Filed under "epidemiology has a 100% track record - it has always been wrong."

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