NUI Galway study challenges blood pressure guidelines

Professor Bill McEvoy of NUI Galway who led a major research study into the implications for patients of new, lower blood pressure guidelines.

Professor Bill McEvoy of NUI Galway who led a major research study into the implications for patients of new, lower blood pressure guidelines.

Up to 150,000 Irish patients may not need to increase their blood pressure medication despite new lower blood pressure thresholds recommended recently in US and European medical treatment guidelines.

According to a major study conducted by NUI Galway this group, who are now eligible for treatment due to a drop in previously recommended blood pressure targets, may not benefit from increasing their dosage or the number of blood pressure medicines they currently take. These findings may impact the national drugs bill ).

The NUI Galway investigation, which was led by Professor Bill McEvoy, was undertaken in collaboration with US investigators and is 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 [the bottom number in blood pressure readings, ie, the pressure in the arteries when the heart rests between beats] threshold of 80 for the diagnosis of hypertension. This new threshold is lower than previous guideline recommendations which 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 study examined a type of high blood pressure or hypertension, termed isolated diastolic hypertension. This occurs when the systolic (top ) number is normal (ie, below 130 according to new guidelines ) but in contrast the diastolic (bottom ) number is high (ie, greater than or equal to 80 according to new guidelines ).

Professor McEvoy and his co-authors report that when applying the new guidelines, approximately five per cent 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 recommend that a target blood pressure of 130/80 is achieved for the majority of adults who are receiving treatment to lower their blood pressure.

The findings from the 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 his collaborators suggests that increases in blood pressure drug therapy may not benefit adults with this pattern of isolated diastolic hypertension. Specifically, they discovered 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 stated that American and European guidelines 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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