Hypertension and diabetes commonly coexist. Both are major modifiable risk factors for cardiovascular diseases. There has been a substantial shift in the recommendations of several expert committees on the management of hypertension in diabetics. It was once unanimously agreed by almost all major guidelines that the threshold for initiating diabetic patients with antihypertensive therapy is when blood pressure is >130/80 mmHg. The blood pressure target for treatment was also unanimously agreed to be <130/80 mmHg. These recommendations were, however, based on expert opinions and not on findings from major randomised controlled trials.
Since then, there have been several randomised controlled trials looking at blood pressure-lowering in the diabetic population. These include the ADVANCE and ACCORD, and a subanalysis of the INVEST trials. Together with the earlier UKPDS and HOT trials, one would expect there to be more agreement in the most recent recommendations, but in fact the opposite is the case. There are now two different systolic targets (<130 mmHg and <140 mmHg) and three different diastolic targets (<90 mmHg, 85 mmHg, and <80 mmHg). The reason for this involves the choice of trials included in the recommendation, and the interpretation of results from these trials by various guideline committees.
The recommendation for diabetic hypertensives will be more consistent if future trials begin by asking a relevant research question that has not yet been answered: does treating diabetics with different thresholds of blood pressure levels impact on clinical outcomes? The trial must not only determine a primary research question, but it must also be adequately powered to answer it. Only when this question is answered should the next questions be asked. Does it matter how blood pressure is lowered? And are some drugs better than others? In the meantime, guideline committees should try to narrow the gap in recommendations, particularly if the guidelines originate from the same country or region.
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