Strict Blood Pressure Control in Diabetics Associated with Fewer Complications

1. Blood pressure lowering in patients with diabetes mellitus type II was associated with a decreased risk of macro- and micro-vascular disease, as well as all-cause mortality.

2. Achieving a systolic BP <130 mmHg was associated with reduced risk of stroke, retinopathy, and albuminuria, with the reduction in risk greatest for albuminuria and stroke.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Diabetes mellitus type II (DM-II) is a known risk factor for macro- and micro-vascular disease. There has been significant controversy regarding blood pressure (BP) control in this patient population and whether more aggressive BP control reduces the risk of vascular disease. This meta-analysis study compiled all trials over the past 28 years that looked at BP-lowering in DM-II patients to determine whether strict BP control truly reduces the risk of vascular disease in diabetics.

The results showed that lowering of BP was beneficial for reducing both macro- and micro-vascular events in patients with DM-II. This study also found that lowering systolic BP below 130 mmHg significantly reduced the risk of stroke, blindness, and worsening of kidney disease. This meta-analysis is the largest trial thus far to evaluate BP control in diabetics. Strengths of the study include its high power to detect small statistical differences and strict requirements for trial inclusion. Study limitations include multiple vascular diseases acting as confounding variables to each other and the difficulty of assessing the benefit of each BP class of medications separately. Nevertheless, given that the Joint National Committee guidelines recently relaxed the threshold of initiating BP-lowering medications in diabetics from >130 mmHg to >140 mmHg systolic BP, this study suggests that the original lower BP targets may be more appropriate for some patients.

Click to read the study, published in JAMA

Click to read an accompanying editorial in JAMA

Relevant Reading: Effect of intensive blood-pressure control in type 2 diabetes mellitus

In-Depth [systematic review and meta-analysis]: This systematic review and meta-analysis of 45 randomized controlled trials over the past 28 years assessed the effect of BP reduction on vascular disease risk, specifically in patients with DM-II. Studies that had less than 1000 patient-years in follow up, that had a majority of DM-I, or in which sub-stratification of the DM-II patient group could not be performed, were excluded. Main outcome measures included all-cause mortality, cardiovascular (CV) events, coronary heart disease (CHD) events, stroke, heart failure, retinopathy, new or worsening albuminuria, and renal failure. Statistical analysis was performed by fixed-effects analysis to minimize bias.

Results demonstrated that each 10 mmHg reduction in systolic BP significantly reduced the risk of all-cause mortality (RR 0.87), CVD events (RR 0.89), CHD events (RR 0.88), strokes (RR 0.73), retinopathy (RR 0.86), and albuminuria (RR 0.83). Reduction in risk was greatest for albuminuria with a number needed to treat (NNT) of 11 and stroke with a NNT of 25. Reduction in risk of these two vascular diseases was regardless of whether initial systolic BP was greater or less than 140mm Hg. Risk of heart and renal failure were not reduced significantly by a 10 mmHg drop in BP but were statistically significant when analyzed against BP-lowering treatment arm and non-BP-lowering arm. Lowering systolic BP to less than 130 mmHg was only statistically significant in reducing risk of stroke, retinopathy, and albuminuria.

 

Source: 2 Minute Medicine