Distilling Clarity from Confusion: Blood Pressure, Heart Disease and Diabetes

In a recent sharepost I discussed lowering blood pressure (BP) and mentioned the new guideline from the National Health, Lung, and Blood Institute of lowering BP to under 120/80 mmHg. As of late, the most recent advice has simply been, "Lower is better!"  Epidemiological studies seem to support this idea noting that those who start with lower BP tend to live longer.  It is also known that BP in children and adolescents start out significantly lower and increase as we age.  Yet we have most recently received conflicting information from new reports studying BP in diabetics.

We all know that diabetes is a major risk factor for heart disease and that those with diabetes are often advised to treat risk factors such as BP aggressively upon a diagnosis of diabetes.  Among heart disease risk factors, high BP is #4 on the famous Framingham Risk Factors list (several places above smoking).  Major studies such as the ADVANCE trial concluded that relatively small decreases in BP, regardless of baseline levels or other treatments, were cardio-protective.

The first unsettling outcome was obtained from a 10-year follow-up of the UKPDS study, a large-scale trial of the effects of glucose and BP lowering in diabetics. The study did show a 15% decrease in heart attack rate from increased glucose control but the results from tighter BP control were disappointing showing no long-term difference when comparing increased therapeutic intervention to decrease BP over less stringent BP control.  Note that blood pressure was lowered in all cases. The study suggested that the "even lower is better" mantra is not universally true.

Perhaps the data that is causing the most commotion comes from a new observational study of the ONTARGET trial. In this study the surprise result was that lowering systolic BP to under 130mmHg may be harmful. One doctor was quoted as suggesting not to treat diabetics to below 140/90mmHg. This is sobering advice for the "lower is better" school of thought and the latest National Heart, Lung, and Blood Institute guidelines.

So what should we as heart health consumers take away from this seemingly paradoxical information?

1. Lowering BP has been a hallmark of good heart health for decades.  Many studies have confirmed this.  But as we all know, there is such a thing as too low.  Certainly a BP of 80/40 would be worrisome (trust me, I was in the emergency room with such a reading)!

2. We are beginning to have a better understanding of just where to draw the line at "too low" but even the curious findings of ONTARGET must be interpreted cautiously.  This population in question was diabetic - not the average person - and even those with the highest blood pressures had poorer outcomes. The only paradox uncovered was a discovery that lowering systolic BP below 130mmHg in diabetics reversed the trend toward superior outcomes as BP continued to drop.  No one knows why just yet.  For example, it could have something to do with other drugs diabetics take.