New Blood Pressure Guidelines: Is There Evidence to Back Them Up?
On November 13th the American College of Cardiology issued new guidelines for blood pressure control, stating that optimal systolic pressure should be pushed below 130 instead of the current number of 140. This change means that half of all American adults, and 80% of those over 65, will now be considered hypertensive. The guidelines suggest that 30 million additional people will benefit from treatment.
According to the New York Times “…Millions More Americans Will Need to Lower Blood Pressure.” While the expert committee drafting the guidelines considered hundreds of studies, the Sprint study from 2015 was the most important determinant of the new recommendations. Citing the Sprint results, Dr. Jeff Williamson of Wake forest states that adherence to lower blood pressure guidelines could reduce the complications from high blood pressure by 30%. The Times article, again using Sprint results, states that more aggressive blood pressure targets will reduce the incidence of stroke, heart attacks, and heart failure by a third, and the risk of death by a quarter (all misleading relative changes).
The Sprint Study looked at 9300 people over the age of 50 who were deemed to be at high risk of heart disease. For those people who had blood pressure over 120, half the participants received an additional medicine to drive the pressure lower. In those participants, cardiac complications dropped by a third and death by a quarter. The study barely discusses nuisance side effects such as dizziness, fatigue, and confusion that can result from low blood pressure, and it does not address whether the improved outcome is related to other benefits of the additional medicines.
But most importantly, the study portrays improved outcome using relative numbers, which are always deceptive. What are the actual risks and benefits of intensive blood pressure treatments? And, do millions of Americans need to lower their blood pressure, as the Times article states, or will they have an opportunity to make an informed decision?
Our BRCTs can be used to illustrate actual risks and benefits from lowering blood pressure. As shown in the BRCT on the left, out of 1000 high risk people who have intensive blood pressure control compared to 1000 who do not, approximately 3.5 people avoid death over three years. Approximately 5 people out of 1000 avert stroke, heart attack, or congestive heart failure over that time. There are down sides of intensive blood pressure control.
As shown in the next BRCT, out of 1000 people who have intensive blood pressure control compared to 1000 who do not, approximately 12 have serious side effects. This includes severe kidney disease in 6 people and life-threatening drops in blood pressure in 3 people.
Many other studies before and after Sprint demonstrate just the opposite result: increased rate of death with intensive blood pressure control.
The HOPE-3 study published a year after Sprint, evaluating people with a moderate risk of heat disease, shows that out of 1000 people who have intensive blood pressure control compared to 1000 people who do not, approximately 8 more people die or have cardiovascular events. A large VA study of people with kidney disease and a 2010 JAMA study of diabetics show a similar or larger increase death rate in people who have their blood pressure lowered below 120. These findings are summarized in the third BRCT on the left.
The decision about whether to push blood pressure below 130 is one that should be made by each person individually using actual data that is most relevant to his/her circumstances. Despite the generic new guidelines, there is little evidence that in many cases aggressive blood pressure control will achieve the dramatic results that are being citied. In fact, there is as much or more chance it can cause harm.