Monday, 8 September 2008

In the news...

Two articles from Medscape that caught my attention.

For starters, there's a comment on US News & World Report's rankings for cardiovascular care. Leading the pack was Cleveland Clinic, followed in turn by the Mayo clinic and Johns Hopkins Hospital. Oh well, better luck next year to the latter two. (Of course, something like this ratings like this are largely just silly, as they are so subjective and so averaged-out that they have almost no individual value.)

Then there was the report on a study that showed a reasonably strong association with vitamin D deficiency and cardiovascular risk. Some people are going as far as to say that vitamin D deficiency could soon be classed alongside things like smoking and hyperlipidaemia as causes of cardiovascular events. To quote:

Melamed and colleagues found those in the lowest quartile of vitamin-D levels had a 26% higher risk of all-cause mortality and a similar increased risk of cardiovascular disease (CVD) mortality, although the latter was not statistically significant. They did not find an association between low vitamin-D levels and cancer mortality or other causes of death, however.

Two fairly straightforward points can be made here. Firstly, just because vitamin D deficiency might increase your cardiovascular risk profile, it does not mean that taking vitamin D supplements if you are not vitamin D deficient will be beneficial. In fact, this might also be bad for you (supplements of vitamins A and E have been implicated in a similar regard!) Secondly, the study mentioned is a classic observational study, which is rather powerless to distinguish a correlation from a cause. (To choose the first example that came into my head, smoking, in addition to increasing your cardiovascular risks, might also lower vitamin D levels. This would account for the findings, while also deny vitamin D any role in the pathogenesis of heart attacks and strokes.) To tease out the actual causal pathways (or lack thereof), we need a randomised control trial, as the study authors themselves acknowledge. An interesting first step, nonetheless.

No comments:

Post a Comment