Hypertension Targets for Diabetes Mellitus Patients

Hypertension is a common comorbidity of diabetes, affecting approximately half of all diabetic patients. High blood pressure increases the risk of vascular complications. Microvascular complications include diabetic retinopathy, neuropathy, and nephropathy, whereas macrovascular complications include coronary artery disease, peripheral arterial disease, and stroke. Intensive blood pressure control is routinely recommended for diabetics to reduce complications, and is known to be more beneficial than strict glycaemic control. Recently released international guidelines, however, suggest utilising more ‘relaxed’ blood pressure goals for diabetic patients.

According to the Heart Foundation’s Guide to Management of Hypertension 2008, the current recommendation is to target a blood pressure of less than 130/80mmHg for diabetic patients. It is yet to be updated to be consistent with the European and American guidelines’ blood pressure goal of 140/90mmHg.

The significance of intensive blood pressure goals in diabetic patients has been addressed in the Action to Control Cardiovascular Risk in Diabetes blood pressure (ACCORD BP) trial, the Normotensive Appropriate Blood pressure Control in Diabetes (Normotensive ABCD) trial, and the Stop Atherosclerosis in Native Diabetics Study (SANDS).

The ACCORD BP trial studied the incidence of major cardiovascular events in type 2 diabetic participants at high risk of cardiovascular events, and treated with intensive therapy to achieve a systolic blood pressure (SBP) goal of less than120mmHg versus standard therapy with a SBP goal of less than 140mmHg. The trial concluded that there was no significant difference in the rate of the composite outcome, of nonfatal and fatal major cardiovascular events, in the specified patient groups with type 2 diabetes. In addition, the intensive therapy group experienced notably more frequent adverse events than the standard therapy group. These included hypotension, arrhythmia, bradycardia, syncope, hyperkalaemia, renal failure, and angioedema. The annual rates of stroke and nonfatal stroke, however, were significantly reduced in the intensive therapy group.

The Normotensive ABCD trial evaluated the effect of intensive versus moderate diastolic blood pressure (DBP) control on diabetic vascular complications. It assigned 480 normotensive (BP <140/90mmHg) type 2 diabetic patients to randomised intensive and moderate DBP control groups. The mean blood pressure for the intensive and moderate groups were 128/75mmHg and 137/81mmHg, respectively. Results showed that over a five year follow-up period, intensive blood pressure control in normotensive type 2 diabetics slowed the progression to incipient and overt diabetic nephropathy, as well as reduced the progression of diabetic retinopathy. The rate of cardiovascular events was not reduced, although the incidence of stroke was significantly decreased.

The SANDS trial compared the progression of subclinical atherosclerosis in type 2 diabetics who were treated to reach aggressive targets, of low density lipoprotein (LDL) cholesterol ≤1.8mmol/L and SBP ≤115 mmHg, against those treated to reach the standard targets of LDL cholesterol ≤2.6mmol/L and SBP ≤130 mmHg. The three year trial demonstrated that although aggressive therapy is associated with less progression of atherosclerosis, it also significantly increases antihypertensive-related adverse events. No difference in clinical cardiovascular events between the two groups was established.

The new evidence used by international guidelines may be useful when the Australian guidelines recommendations are reviewed for blood pressure targets in diabetic patients. As per recommendations of the major guidelines published by the European Societies of Hypertension and Cardiology (ESH/ESC) and the Eighth Joint National Committee on the Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 8), the blood pressure target for all patients with type 2 diabetes mellitus should be less than 140/90mmHg. The more intensive blood pressure goal of 130/80mmHg should be attempted with caution, due to antihypertensive side effects, and is only recommended for patients with diabetic nephropathy and proteinuria, where at least 500mg of protein is eliminated in the urine daily.