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464,000 people can’t be wrong, or can they?

Carl Heneghan
Last edited 7th June 2009
In this week’s BMJ Law and colleagues have undertaken a notable meta-analysis on the use of blood pressure lowering treatments from randomized controlled trials. For the BMJ this is an impressive piece, signalling a potential return to some of the significant research published in the past. For instance, in the early 90s nearly a whole edition of the BMJ was given over to the aspirin triallist collaboration systematic reviews. In those days, all of the report appeared in the print version, whereas today the print version carries a meagre synopsis whilst the pdf downloadable from the web runs to an impressive 19 pages. So what does it mean? Well, in the first instance it is difficult to digest the whole message in one sitting. It may take a few reads to get your head round the methods and the findings. My viewpoint is that from 147 RCTs with 464,000 people no one type of antihypertensive is better that another. This was already pretty well known: the benefit is all in the blood pressure reduction. Apart from a few exceptions: beta blockers after myocardial infarction and a small benefit of calcium channel blockers in prevention of stroke. The most interesting point is the major blood pressure reduction achieved with half doses of medications compared to full dose. For example, 3 drugs at half standard dose achieved a 27 mmHg reduction in blood pressure in patients with an in initial blood pressure of 180mmHg; whereas two drugs at standard dose only achieve a 22mmHg reduction (32 mmHg for 3 drugs at standard dose). Finally, this paper starts the debate about whether there is an actual condition called hypertension. They conclude that guidelines could be changed whereby all people would receive therapy irrespective of the level of blood pressure once they reach a certain age or cardiovascular risk. We will soon hear the call for the polypill for everyone; but beware of those with a vested interest. I’m not sure if this is the right direction; what we really need is better risk prediction so we can target therapies to those at most risk.
  1. Use of blood pressure lowering drugs in the prevention of cardiovascular disease: meta-analysis of 147 randomised trials in the context of expectations from prospective epidemiological studies. BMJ 2009 May 19;338:b1665. doi: 10.1136/bmj.b1665. Law MR, Morris JK, Wald NJ.

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