Antihypertensive treatment may harm diabetic patients with SBP < 140 mm Hg

Brunström M, Carlberg B.
BMJ 2016;352:i717

Background

Optimal blood pressure (BP) goals in patients with diabetes (DM) are topic of debate [1,2]. While past guidelines recommended BP < 130/80 mm Hg, current guidelines recommend BP < 140/90 mm Hg or lower targets [3-6].
Recent review data show, however, that BP-lowering therapy in individuals with SBP < 140 mm Hg is associated with a reduced risk of stroke and albuminuria, a finding that challenges the < 140 mm Hg target, as it may be too high [7]. On the other hand, previous observational studies have described a J-shaped or U-shaped curve for the relationship between BP and CV events [8,9], which might be explained by the impairment of blood flow to end organs leading to ischaemia, due to intensive treatment [10].
In this systematic review and meta-analysis of 49 randomised controlled trials, the effect of BP-lowering treatment on mortality and CV morbidity at different blood pressure levels was assessed in 73738 patients with DM, using previously published and unpublished data.  

Main results

If baseline SBP was greater than 150 mm Hg, antihypertensive treatment reduced the risk of:

• All-cause mortality (RR: 0.89; 95%CI: 0.80 - 0.99)
• CV mortality (RR: 0.75; 95%CI: 0.57 - 0.99)
• myocardial infarction (RR: 0.74; 95%CI: 0.63 - 0.87)
• stroke (RR: 0.77; 95%CI: 0.65 - 0.91)
• end stage renal disease (RR: 0.82; 95%CI: 0.71 - 0.94)

If baseline SBP was 140-150 mm Hg, additional antihypertensive treatment reduced the risk of:

• all-cause mortality (RR: 0.87; 95% CI: 0.78 - 0.98)
• myocardial infarction (RR: 0.84; 95% CI: 0.76 - 0.93)
• heart failure (RR: 0.80; 95% CI: 0.66 - 0.97)

If baseline SBP was less than 140 mm Hg, additional antihypertensive treatment:

• increased the risk of CV mortality (RR: 1.15; 95% CI: 1.00 - 1.32)
• tended to increase the risk of all-cause mortality (RR: 1.05; 95% CI: 0.95 - 1.16)

Meta-regression analyses showed a worse treatment effect with lower baseline SBP for:

• CV mortality (RR: 1.15; 95% CI: 1.03 - 1.29 for each 10 mm Hg lower SBP)
• myocardial infarction (RR: 1.12; 95% CI: 1.03 - 1.22 for each 10 mm Hg lower SBP)

Conclusion

A large systematic review and meta-analysis shows that antihypertensive treatment reduces the risk of mortality and CV morbidity in patients with DM and SBP > 140 mm Hg at baseline. In patients with DM and SBP < 140 mm Hg at baseline, antihypertensive treatment provides no benefit and is associated with an increased risk of CV death. These data suggest that the interaction between SBP before treatment and the treatment effect is significant, and that SBP before treatment modifies the effect of treatment in a causal way.

Find this article online at the BMJ

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