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How Low is Too Low? Blood Pressure Goals for Diabetic Patients

Research indicates setting more aggressive blood pressure goals for diabetic patients may cause harm.

As guidelines are updated, the recommendations for treating blood pressure also change.  As of today, the American Diabetes Association (ADA) recommends treating hypertension in diabetic patients if their blood pressure is above 140/90.  In January 2016, a new systematic review was published in the BMJ that looked into the studies that re-evaluated this recommendation.

The authors looked at 49 randomized controlled trials (RCTs), which included 73,738 participants, of whom most had diabetes mellitus. CENTRAL, Medline, Embase, and BIOSIS databases were used for a search. In the analyzed studies, most diabetes patients were followed for at least 12 months with the mean of 3.7 years.  The authors’ final review and meta-analyses were stratified by entry and systolic blood pressure (SBP) goals.

The results of a review clearly state that we should not treat patients’ blood pressure if it is less than 140. Authors analyzed risks for multiple negative health events for which all diabetes patients are especially in danger of death as compared to the rest of our population and their risk of death.  All cause mortality was reduced if SBP was 140-150 mmHg before treatment (relative risk 0.87, 95% confidence interval 0.78-0.98) or above 150 mmHg (relative risk 0.89, 95% confidence interval 0.80-0.99) and 130-140 mmHg after treatment (relative risk 0.86, 95% confidence interval 0.79-0.93). If the starting SBP was less than 140 mmHg and it was treated with medications, it increased patients’ risk for mortality (relative risk 1.05, 95% confidence interval 0.95-1.16). Also, if patients achieved SBP less than 130, it increased their odds for mortality (relative risk 1.10, 95% confidence interval 0.91-1.33). Cardiovascular mortality was reduced if starting SBP was above 140 mmHg (relative risk 1.15, 95% confidence interval 1.00-1.32) or attained SBP was above 130 (relative risk 0.86, 95% confidence interval 0.72-1.04) or even above 140 mmHg (relative risk 0.87, 95% confidence interval 0.71-1.07). The risk for myocardial infarction decreased if patients’ baseline blood pressure was 140-150 mmHg (relative risk 0.84, 95% confidence interval 0.76-0.93) or above 150 mmHg (relative risk 0.75, 95% confidence interval 0.57-0.99). The risk of heart failure decreased if patients were treated for hypertension even when participants’ baseline blood pressure was less than 140 mm Hg (relative risk 0.90, 95%, confidence interval 0.79-1.02). The relative risk of end-stage renal disease increases from 0.82 if patients’ blood pressure before initiation of a therapy is above 150 mm Hg (95% confidence interval 0.71-0.94) to 0.97) for starting SBP less than 140 mmHg (95% confidence interval 0.80-1.17). Despite the fact that a lot of presented data is not statistically significant, the findings of the study could be significant in clinical settings.

Additionally, authors of the study conducted meta-regression of the analyzed data and found that the risk of cardiovascular death increased 28% for each 10 mmHg lower baseline diastolic blood pressure (DBP).  The blood pressure medication treatment was not beneficial unless patients’ DBP was above 78 mmHg.

Although the exact reason is unknown for why treating blood pressure too early can lead to adverse effects, the theory is that too strict control of blood pressure decreases the blood flow to the end organs, leading to ischemia. When blood hypoperfusion is combined with arterial stiffening that is already present in most diabetes patients, it is clear that blood pressure goals for diabetes patients should be more relaxed than for the rest of our population. Moreover, patients with low blood pressure experience reduced endothelial stress and as a result have less arteriogenesis, which could lead to cardio events and coronary occlusions. This hypothesis not only explains pathophysiology of the cause of these life-threatening events, but also warns that in case of a patient experiencing a negative health event, his chances for survival diminish as blood perfusion to his organs is impaired. Given this information, healthcare providers should be vigilant about not treating blood pressure prematurely in the diabetes patient population.

Practice Pearls:

  • In patients with diabetes and SBP more than 140 mm Hg, treatment with antihypertensive medications is associated with decreased risk of mortality and cardiovascular comorbidities.
  • In patients with diabetes and SBP less than 140 mm Hg, treatment with antihypertensive medications is associated with increased risk of cardiovascular mortality.
  • SBP is a more accurate indicator of a risk of cardiovascular disease and a tool that reflects about 95% of cardio events, while DBP is not as good of a marker as it is often confounded by the differences in patients’ pulse rate.

Researched and prepared by Renata Kulawik, Doctor of Pharmacy Candidate LECOM College of Pharmacy, reviewed by Dave Joffe, BSPharm, CDE

 

Brunström, Mattias, and Bo Carlberg. “Effect of antihypertensive treatment at different blood pressure levels in patients with diabetes mellitus: systematic review and meta-analyses.” bmj 352 (2016): i717.