''The guidelines suggest you want diabetics to have [systolic pressure] under 130," says researcher Rhonda M. Cooper-DeHoff, PharmD, associate professor of pharmacy and medicine at the University of Florida, Gainesville.
But in her study, those who kept their systolic pressures moderately controlled -- at 130 to 139 -- did as well as those who controlled it more tightly. Systolic pressure is the upper of the two blood pressure numbers, representing the maximum pressure exerted when the heart contracts.
She compared ranges of blood pressure control on the effect on death, heart attack, and stroke during the follow-up. "There was no difference comparing those with tight control or usual control," she tells WebMD, "which is contrary to what the guidelines would suggest."
''The message is: we need to get diabetic patients' systolic blood pressure to less than 140, particularly when they have heart disease, but working to get it to less than 130 does not appear to add any additional benefit with regard to the risk of death, stroke, or heart attack," Cooper-DeHoff says.
The study is published in the Journal of the American Medical Association.
Tight Control of Blood Pressure vs. Moderate Control
For this study, Cooper-DeHoff and colleagues looked at a subgroup of 6,400 participants of a large study, called INVEST (International Verapamil SR-Trandolapril Study). It included more than 22,000 participants from 14 countries who were at least 50 years old and had high blood pressure and coronary artery disease.
Study participants enrolled in the study from 1997 to 2000 and were followed through March 2003, with follow-up for U.S. participants extended through August 2008.
For this analysis, the researchers focused only on the 6,400 who also had diabetes at the study start.
INVEST compared two blood pressure lowering approaches, with participants given either a calcium antagonist medication first or a beta-blocker medication, followed by more drugs if needed to lower pressure.
Next, the researchers categorized the 6,400 participants into three groups:
- 35.2% had tight control, with systolic pressure maintained at below 130.
- 30.8% had moderate or usual control, with pressures from 130 to under 140.
- 34% had uncontrolled, with pressures above 140.
Moderate Control of Blood Pressure Wins Out
Little difference was found between the tight control and moderate control groups. Of the 6,400:
- 12.7% who had tight control died or had a heart attack or stroke.
- 12.6% of those with moderate control did.
- 19.8% of those with uncontrolled blood pressure did.
During the extended follow-up period, the risk of death from any cause was actually higher in the tight control group, 22.8%, vs. those in the moderate control group, 21.8%.
Cooper-DeHoff cautions that the results can't be generalized to those who have diabetes but not coronary artery disease.
Even though the guidelines recommending lower blood pressures in those with diabetes have been in place for nearly 20 years, she writes, ''there is a paucity of evidence supporting this recommendation, particularly for lower systolic blood pressure."
Cooper-DeHoff reports receiving research funds from Abbott Laboratories, which makes blood-pressure-lowering drugs.
''This is good news all the way around," says P.K. Shah, MD, a cardiologist and director of the division of cardiology at the Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, who reviewed the study findings for WebMD.
The take-home message for those like the participants, he says, is that moderate blood pressure control is a reasonable range to shoot for. "This is saying moderate control of blood pressure is effective."
Other research finds that those with naturally low blood pressure are at reduced risk for problems such as heart attack and stroke, Shah says. "But drug-induced lowering [of blood pressure] is not the same as natural low blood pressure," he says, explaining that blood pressure lowering by drugs does not mimic all the good effects of having naturally low pressure.