January New NUI Galway Study Challenges Blood Pressure Guidelines

Despite recommendations to intensify treatment in recent blood pressure guidelines, as many as 150,000 Irish patients may NOT need to increase blood pressure medication

Embargo to 00.01 GMT on Wednesday, 29 January, 2020: A major research study from NUI Galway has interrogated the implications for patients of new, lower, blood pressure thresholds recommended in recently released American and European medical guidelines for the treatment of high blood pressure (also termed hypertension). 

The findings from this NUI Galway study indicate that up to 150,000 Irish adults who are newly eligible for treatment to a lower than previously recommended blood pressure target, may in fact not benefit from increases in their doses or number of blood pressure medications. This may have knock on implications for the national drugs bill.

The NUI Galway investigation, led by Professor Bill McEvoy, was conducted in collaboration with US investigators and is now published in a leading international medical journal, the Journal of the American Medical Association (JAMA).

The investigators looked specifically at the new American diastolic blood pressure threshold of 80 for the diagnosis of hypertension.  This new diastolic blood pressure threshold of 80 was a reduction from prior guideline recommendations that advised doctors to use a diastolic blood pressure of 90 or more to make a diagnosis. Diastolic blood pressure is the lower of two readings reported when describing blood pressure values, the other, top, number is called systolic blood pressure. High blood pressure can be diagnosed when either the systolic or diastolic (or in some cases both) numbers are above the threshold value.

The NUI Galway investigation looked at a type of high blood pressure or hypertension, termed isolated diastolic hypertension. This occurs when the systolic (top) number is normal (i.e., below 130 according to new guidelines) but in contrast the diastolic (bottom) number is high (i.e., greater than or equal to 80 according to new guidelines). 

Professor McEvoy and coauthors report that, when applying the new guidelines, approximately 5% of the US adult population will be newly diagnosed with high blood pressure (or hypertension) based on this pattern of isolated diastolic hypertension. That translates into approximately 12 million adults in the US being newly diagnosed with this condition. The corresponding Irish figure would be 100,000 new cases.

Though there are differences between American and European guidelines in how high blood pressure is defined, both sets of guidelines recommend that a target blood pressure of 130/80 be achieved for the majority of adults who are receiving treatment to lower their blood pressure. Therefore, the findings from this NUI Galway study have implications for Irish adults in that approximately 600,000 are already on treatment for high blood pressure and up to 150,000 of these may now be newly eligible for increases in their treatment doses or number of medications just to get the diastolic (lower) number to less than 80 despite having a normal systolic (top) blood pressure of below 130. However, the research from McEvoy and collaborators suggests that increases in blood pressure drug therapy may not benefit adults with this pattern of isolated diastolic hypertension. Specifically, they found that as long as the systolic (or top) blood pressure was below 130, there was no increase in risk for adverse health outcomes among adults with a diastolic blood pressure over 80, compared to adults with lower diastolic blood pressure values.

Professor McEvoy said: “Guidelines in both America and Europe advise that doctors treat blood pressure down to a level of 130/80 in the majority of patients. There is little doubt that treating the systolic (or top) blood pressure value down to 130 is beneficial and reduces heart disease and stroke. This is important to stress. However, the recommendation to also treat the diastolic (lower) value down to 80 is more controversial and our results would suggest that the more traditional target for diastolic blood pressure of 90 is also safe as long as the top number is controlled below 130. By focusing on good control of the top number and by relaxing drug treatment goals for adults with isolated increases in the bottom diastolic blood pressure number, we may be able to avoid potential overtreatment of a lot of people and instead focus on healthy diet and lifestyle.”

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