Doctor examining his patients blood pressure in medical office


The findings of a major research study from The National Institute for Prevention and Cardiovascular Health (NIPC) and The National University of Ireland Galway (NUIG) call into question the validity of recent changes to treatment recommendations for a certain type of blood pressure patient.

The study has challenged an element of the new, lower, blood pressure thresholds recommended in recently released American medical guidelines for the diagnosis and treatment of high blood pressure (also termed hypertension).  These US guidelines changed the definition of hypertension from a blood pressure of 140/90 or more, to a blood pressure of 130/80 or more. Subsequently, guidelines from European clinical societies also recommended that most adults being treated for high blood pressure be treated to the new lower target of 130/80.

These high blood pressure guidelines are observed widely in Ireland and as a result, as many as 150,000 patients with a bottom blood pressure number of over 80, but a normal top blood pressure number below 130 are potentially at risk of being over-treated according to the NIPC/NUIG research. This is because the study found that this specific type of blood pressure pattern does not appear to be adversely affecting their health. Of note, blood pressure levels are denoted by two numbers, one above the other where, for example, a blood pressure level may be written as 130/80.  The top number is known as the systolic, and the bottom number is known as the diastolic reading.

The NIPC and NUIG investigation, led by Prof J William McEvoy, Medical and Research Director of the NIPC, was conducted in collaboration with US investigators and is today published in a leading international medical journal, the Journal of the American Medical Association (JAMA).

The JAMA published investigation looked specifically at the new (lower number) diastolic blood pressure threshold set at 80 for the diagnosis of elevated blood pressure, which was a reduction from a prior diastolic blood pressure of 90. The recommendation to lower the diastolic threshold for hypertension from 90 to 80 was based on expert opinion (which is a relatively weak type of evidence), not on results from clinical trials (with the latter considered to be the strongest type of medical evidence). 

A specific group of patients is now eligible to be diagnosed with high blood pressure as a result of this changed threshold.  These patients suffer from Isolated Diastolic Hypertension, characterised by a normal systolic (top) number (i.e., below 130 according to new guidelines) but a higher diastolic (bottom) number (i.e., greater than or equal to 80 according to new guidelines).

The report states that approximately 5% of the US adult population are newly diagnosed with high blood pressure (or hypertension) based on the definition for isolated diastolic hypertension contained in the new guidelines. This translates into approximately 12 million adults in the US being newly diagnosed with this condition.

“Though there are differences between American and European guidelines in how high blood pressure is defined, in general both sets of guidelines recommend that a target blood pressure of 130/80 be achieved for those who are receiving treatment to lower their blood pressure”. 

Professor McEvoy, Medical and Research Director, the NIPC

He continued: “The findings from this NIPC/NUIG study have implications for Irish adults since approximately 600,000 are already on treatment for high blood pressure and as many as 150,000 of these may now be eligible for increases in their treatment doses or number of medications.  Their clinicians could now be aiming to get the diastolic (lower) number to less than 80 despite the patient having a normal systolic (top) blood pressure of below 130”. 

He concluded: “This is a concern, because our team found no adverse health outcomes from a diagnosis of Isolated Diastolic Hypertension when the new guideline criteria are used. The absence of negative health outcomes in this group challenges the need to intensify the blood pressure treatment of these adults with higher diastolic blood pressure. Instead the main focus should be on getting the top number (or systolic blood pressure) under control”.


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