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In diabetes, the benefits of BP-lowering drugs depend on systolic BP being 140 mm Hg or more before starting treatment

Brunstrom M, Carlberg B Effect of antihypertensive treatment at different blood pressure levels in patients with diabetes mellitus: systematic review and meta-analyses. BMJ. 2016 Feb 24;352:i717.

Review question

In people who have diabetes, what is the effect of blood pressure (BP)-lowering drugs when people start with different BP levels?

Background

People with diabetes have a higher risk of cardiovascular disease and often also have high BP. High BP is usually defined as having a systolic BP of 140 mm Hg or more or a diastolic BP of 90 mm Hg or more. High BP often doesn’t cause symptoms, but over time it can cause strokes or heart problems, including heart attacks.

Drugs used to lower high BP can reduce risk of cardiovascular events, although they may work differently in people with mild high BP.

How the review was done

The researchers did a systematic review, searching for studies published up to February 2013. They found 49 randomized controlled trials with 73,738 people.

The key features of the trials were:

  • people had diabetes;
  • drugs were given to lower BP;
  • drugs were compared with placebo in most trials;
  • and people were treated for at least 1 year.

The researchers grouped the studies by the average systolic BP at the beginning of the trials.

Outcomes were death, cardiovascular death, heart attack, stroke, heart failure, and end-stage renal (kidney) disease.

What the researchers found

When the average systolic BP was higher than 150 mm Hg at the beginning of the trial (before the trial treatment was started), BP-lowering drugs decreased all-cause death, cardiovascular death, heart attack, stroke, and end-stage renal (kidney) disease.

When the average systolic BP was between 140 and 150 mm Hg at the beginning of the trial, BP-lowering drugs decreased all-cause death, heart attack, and heart failure.

When the average systolic BP was less than 140 mm Hg, BP-lowering drugs showed a borderline increase in cardiovascular death and did not show differences for the other outcomes.

Conclusion

In people who have diabetes and systolic BP of 140 mm Hg or higher, BP-lowering drugs decrease death and heart attacks. In people with systolic blood pressure less than 140 mm Hg, BP-lowering drugs do not decrease death and may be linked to a higher risk of cardiovascular death.

Effect of blood pressure–lowering drugs vs placebo* at different blood pressure levels in patients with diabetes

Outcomes

Average systolic blood pressure (BP) at the beginning of the trials (before the start of treatment)

 

Systolic BP higher than 150 mm Hg

Systolic BP between 140 to 150 mm Hg

Systolic BP less than 140 mm Hg

All-cause death

1% to 20% decrease

2% to 22% decrease

No difference

Cardiovascular death

1% to 43% decrease

No difference

0% to 32% increase

Heart attack

13% to 37% decrease

7% to 24% decrease

No difference

Stroke

9% to 35% decrease

No difference

No difference

Heart failure

No difference

3% to 34% decrease

No difference

End-stage renal (kidney) disease

6% to 29% decrease

No difference

No difference

*Most trials compared BP-lowering drugs with placebo.




Glossary

Diastolic
The lower number in a blood pressure reading. It is the pressure when the heart rests between beats.
Placebo
A harmless, inactive, and simulated treatment.
Randomized controlled trials
Studies where people are assigned to one of the treatments purely by chance.
Systematic review
A comprehensive evaluation of the available research evidence on a particular topic.
Systolic
The higher number in a blood pressure reading. It is the pressure in the arteries when the heart beats.
Vascular
The body's network of blood vessels. It includes the arteries, veins, and capillaries that carry blood to and from the heart.
Vascular death
Death from circulatory problems.

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