Hypertension affects the vast majority of individuals with type 2 diabetes and many of those with type 1 diabetes also. Its pathogenesis is complex, involving interactions between genetic predisposition and a range of environmental factors that include sodium retention, obesity, premature arterial stiffening and endothelial dysfunction (1). Not only are patients with diabetes more likely to have coexistent hypertension, but, for any given systolic pressure, diabetes also is associated with an increase in the age-adjusted cardiovascular death rate.
Fortunately, several, large-scale, multicentre clinical trials have shown that antihypertensive therapy is highly effective at reducing death and disability in people with diabetes (1). These clinical trials also have provided some guidance in the choice of antihypertensive therapy, particularly among those with nephropathy or at high cardiovascular risk. Most recently, much discussion has focused on selecting an appropriate, evidence-based target for systolic blood pressure (SBP). These discussions have, to a large extent, been precipitated by the findings of the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial, which compared the effects of targeting SBP <140 mm Hg with that <120 mm Hg (2). While the primary outcome (a composite of myocardial infarction, stroke, and cardiovascular death) was not significantly different between the 2 groups, stroke, a prespecified outcome, was reduced by 41% in the group targeted to achieve the <120 mm Hg systolic target. The findings of ACCORD are further supported by 2 meta-analyses, which similarly show that (3,4):
Little, if any, additional reduction in cardiac events is achieved by lowering SBP to <140 mm Hg.
Additional reduction in stroke can be achieved by lowering SBP to <120 mm Hg.
Lowering SBP is associated with an increased risk of adverse events, such as hypotension and hyperkalemia. However, the majority of these are associated with SBP <120 mm Hg.
Together, these findings provide the rationale for the current Canadian Hypertension Education Program (CHEP) and the Canadian Diabetes Association harmonized clinical practice recommendations, which continue to recommend blood pressure targets of <130/80 mm Hg in hypertensive patients with diabetes (5).
Persons with diabetes mellitus should be treated to attain SBP <130 mm Hg [Grade C, Level 3 (6,7)] and DBP <80 mm Hg [Grade B, Level 1 (8)]. (These target BP levels are the same as the BP treatment thresholds). Combination therapy using 2 first-line agents may also be considered as initial treatment of hypertension [Grade C, Level 3 (9,10)] if SBP is 20 mm Hg above target or if DBP is 10 mm Hg above target. However, caution should be exercised in patients in whom a substantial fall in BP is more likely or poorly tolerated (e.g. elderly patients, patients with autonomic neuropathy).
For persons with cardiovascular or kidney disease, including microalbuminuria, or with cardiovascular risk factors in addition to diabetes and hypertension, an ACE inhibitor or an ARB is recommended as initial therapy [Grade A, Level 1A (11–14)].
For persons with diabetes and hypertension not included in the above recommendation, appropriate choices include (in alphabetical order): ACE inhibitors [Grade A, Level 1A (15)], ARBs [Grade A, Level 1A (12)], dihydropyridine CCBs [Grade A, Level 1A (15)], and thiazide/thiazide-like diuretics [Grade A, Level 1A (15)].
If target BP levels are not achieved with standard dose monotherapy, additional antihypertensive therapy should be used [Grade D, Consensus]. For persons in whom combination therapy with an ACE inhibitor is being considered, a dihydropyridine CCB is preferable to hydrochlorothiazide [Grade A, Level 1A (16)].
ACE, angiotensin-converting enzyme; ARB, angiotensin receptor blocker; BP, blood pressure; CCB, calcium channel blocker; DBP, diastolic blood pressure; SBP, systolic blood pressure.