Googling around for 'health care blog', the Health Care Blog comes up early in the search.
Overall, the site seems informative on health issues. However, on reading this recent post about the dangers of diet soda consumption, it strikes me that perhaps the blogger didn't really read the article referred to.
The article in question, by Vasan et. al, regarding the risk of soda consumption on progression to metabolic syndrome, emanates from another subset analysis of the famed Framingham study. And upon reading the lay media's conclusion that Vasan's articles shows that drinking diet sodas doesn't decrease the risk of metabolic syndrome (relative to regular sodas), the blogger comments:
"No difference in my on-rushing likelihood of heart disease--according to the latest iteration of the Framingham study—the long running study of 9,000 patients in Massachusetts.
Might as well go back to the chocolate malts…."
Um...no...neither the original Vasan et al. article in Circulation nor the Yahoo story says any such thing. Let's get to the easy part first, the Yahoo story. Three paragraphs into the story, we find this:
"The study's senior author, Dr. Vasan Ramachandran, emphasized the findings don't show diet sodas are a cause of increased heart disease risks. But he said they show a surprising link that must be studied."
Ok, now let's get to the actual article by Vasan et al. They describes a cohort study where a group of people who drank <1 soda per day were compared over time with another group of people who drank >1 soda per day. After about 4 years, the group which comprised soda drinkers, had increased odds of acquiring metabolic syndrome (Odds ratio: 1.44, 95% confidence interval 1.20-1.77).
So does this mean that one's odds of ending up with metabolic syndrome increase with soda consumption? Or that decreasing soda consumption will invariably decrease metabolic syndrome? NOT AT ALL. All it means is that soda drinkers have an association with metabolic syndrome, not that soda drinking causes metabolic syndrome.
(It would be akin to arguing that since no two countries who have a McDonald's have attacked each other, if we build a McDonald's in every country, we'd end up with world peace! - oh wait, Thomas Friedman already made a similar esteemable point.)
Moreover, in cohort studies like this one, odds ratios of <3 mean very little. So the whole point of the paper, that soda consumption may increase the odds of a person having metabolic syndrome, doesn't even meet the threshold of clinical significance. In the end, given that we can't find a causation for any type of soda, surely we can't make any conclusions about a particular subset of sodas!
(Public disclaimer - I live on at least 6 Diet Cokes a day, so if you're going to bring some pansy epidemiological reason I should stop, at least bring your "A" game...)
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