Reference: BMJ2016; 352:I717
Summary:
This systematic review found that lowering systolic blood pressure in diabetics helped some, and hurt others. When the systolic blood pressure was over 140, there was a reduction in all caused mortality, myocardial infarction, and heart failure. But if systolic blood pressure was initially less than 140 mmHg, there was an increase in cardiovascular mortality with a possible increase in all caused mortality. The data also demonstrated the lower the baseline systolic blood pressure, the higher the cardiovascular mortality and myocardial infarction risk.
Methods:
This systematic review and meta analysis reviewed over 40 trials and covering over 70,000 patients. The majority of these patients had type 2 diabetes.
When they compared initial systolic BP to initiation of anti-hypertensive treatment, they found treatment when the systolic blood pressure was greater than 150 millimeters of mercury had the best effect on all caused mortality (relative risk = 0.89*), cardiovascular mortality (relative risk = 0.75*), myocardial infarction (RR = 0.74*), stroke (RR = 0.77*), and end stage renal disease (RR = 0.82*). When systolic blood pressure was between 140 and 150 mmhg, treatment resulted in a decrease in all caused mortality, myocardial infarction and heart failure.
The concerning outcome was when baseline systolic blood pressure was less than 140 mmhg, where it caused an increase in cardiovascular mortality. The data went on to further demonstrate the lower the baseline systolic blood pressure the greater the risk for cardiovascular mortality (RR = 1.15* for each additional 10% mmHg lower systolic blood pressure) and myocardial infarction (RR = 1.12* for each 10 mmHg lower systolic blood pressure).
Conclusions:
Despite what may be inferred from some national guidelines regarding diabetes control, initiation of blood pressure medications (often under the guise of slowing or preventing diabetic nephropathy) may increase adverse outcomes when the systolic blood pressure is less than 140 mmHg.
Discussion:
Information overload can lead providers to make decisions about initiating treatment in complex patients that we hope provide a benefit. This study demonstrates the harms of starting a diabetic patient on an anti-hypertensive, typically ACEi, without systolic hypertension. This level of aggressiveness is actually counter-productive and increases significant adverse outcomes including cardiovascular mortality, myocardial infarction, etc.
The medical model encourages us to be aggressive in how we approach care. Time limitations on visits also pressure us to be aggressive. Add in the multiple and mixed messages in the literature, and the results can lead to over treatment, and harm. For example, the SPRINT trial published last year seem to imply that aggressive blood pressure lowering improved outcome. This was only true in certain populations and for this discussion, the SPRINT trial did not include diabetic patients.
To be certain, aggressive glucose lowering in type 2 diabetics who have not been initially aggressive in their self-care (diet, excecise, etc.) can lead to far more adverse outcomes than benefit. This has been demonstrated repeatedly and yet the message we infer is to “reduce the A1C”. Aggressive lowering of A1C levels using agents that can induce hypoglycemia are more apt to cause an adverse outcome (like increases in mortality) than any benefit. Likewise, aggressive use of anti hypertensives in diabetics, when their systolic blood pressure does not warrant it, also increases the risk of adverse outcomes.
The greatest dilemma here is what to do with the patient whose systolic blood pressure is less than 140 and diastolic is above 90. This study was unable to discern the answer to this question. Conventional wisdom states you treat both systolic and diastolic hypertension and thus judicious use of anti hypertensives is indicated. But like our previous non-evidence based conclusions about aggressive treatment of type 2 diabetes and use of ACEi inhibitors, this conclusion remains to be answered in the future. And, what to do about those “quality measures?” If you are receiving incentives to get the BP “low”, show them this study.
