The Antidote

Counterspin for Health Care and Health News

Tuesday, February 13, 2007

Not ready for prime time

...and yet that's just where it is.

Reuters today published a story linking vasectomy with primary progressive aphasia. Spurred by a patient with aphasia who noted that his symptoms began two years after vasectomy surgery, the researchers looked at a small sample (n=114) of men with and without aphasia, and found that 40% of aphasia patients had had a vasectomy and 16% had not. On the face of it, it looks like there may be something to it - hence the news story.

The problems:

1. Very small sample. Not tiny, but quite small. Too small, probably, to adjust appropriately for other explanatory factors. 40% of 47 men with aphasia is 19, and you don't want to break that number down much more.

2. Retrospective design. Subjects with aphasia may have been more likely to report having a vasectomy, particularly if they knew about the study hypothesis. Unlikely, perhaps - vasectomy is probably for most people a memorable event - but people have been known to forget about medical procedures.

3. Lack of context. That's because there isn't any - according to PubMed it's the first study to look at this hypothesis. As an epidemiologist, I'd say, hmm, interesting finding - let's do a bigger, better study and check it out, and let's do an animal study, say, to look more closely at the idea that antibodies against sperm could affect the brain.

What I wouldn't do is to go to the newspapers with it.
Sandra Weintraub, who led the study, acknowledged that the research involved a small number of people and said she planned to conduct a larger national study to see if the findings hold up. In the mean time, she said her findings should not stop men from getting vasectomies.

"I was hoping not to, but unfortunately it's the kind of news that ends up scaring people even though they may not need to be scared," Weintraub said in an interview.

Hoping not to what? Scare people? She's right; this is just the kind of story that does scare people. So why'd she agree to the interview? Couldn't she just have told the reporter not to bother?

Now there's a question. If any scientists out there have ever told a reporter not to bother with their work, or if journalists have ever heard that from a scientist, I'd like to know.

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