HRT shrinks women's brains? What's wrong with this picture?

There was a widely reported story today about hormone replacement therapy (HRT) and a decrease in the size of women’s brains. The headlines were predictably but needlessly sensational. In fact, the study did not measure a decrease in the brain size of any individual woman.

Source: Richard Amsel, The Movie Posters

First, the headlines. There were 27 stories listed when I checked Google news this afternoon. 19 of these (70 percent) used the word “shrink,” definitely a frightening choice of words when talking about one’s brain. Five stories (18.5 percent) used a less provocative descriptor: brain-tissue loss… reduced brain size… reduction in brain volume… affects brain mass… loss of brain tissue… You get the idea. Three stories (11 percent) elected not to refer to brain size in the headline. But two of those talked about brain “shrinkage” in the first paragraph, another waited until the third. So all of these stories led you to believe that the brains of women on HRT got smaller.
The rush of stories was based on two papers published in the January 13 issue of Neurology. The primary paper analyzed brain scans for abnormal tissue (lesions) in blood vessels. The second paper analyzed MRIs of the brain and reported:

Much to our surprise, we found a small but significant decrease in the hippocampal and frontal volumes, and a nonsignificant trend towards reduced total brain volume in women who had been randomized to hormone therapy.

I haven’t had an opportunity to see the original study, but none of the quotations I have seen use the word “shrink.”

A decrease in volume can legitimately be called shrinkage. But my objection to the headlines is not simply the choice of words. In defense of journalists, the selection of a headline is often beyond their control. And most of the headline writers used a qualifier such as “might,” “may,” “can” or “linked to.” Yet the Washington Post said simply “HRT Shrinks the Brain.”
No, my more basic objection is that the study did not actually show a decrease in brain size. When the article states a “decrease … in total brain volume,” it’s referring to a difference in brain volume between two groups of women: Those who were on HRT and those who took a placebo. But brain volumes were not measured at the start of the study — it was only at the end of the clinical trial that brain measurements were taken and a difference between the two groups observed.
So in fact there was no way to compare the brain volume of any individual before and after HRT, and certainly no way to show that any “shrinkage” occurred. Based on this study there’s no way of knowing if brain volume before taking HRT was already low, or if brain volume changed over the course of treatment. Testing for that would be simple enough (not that I’m offering to volunteer), but it’s definitely not what this study shows.
These Incredible Shrinking Woman headlines are typical of the sensationalism used to promote health news and keep us coming back for more scary stories. The reporting is an example of misrepresenting science news. Let’s keep it honest, folks. We have enough bad news already.