There is uncertainty over the threshold values for diagnosing hypertension

According to recent estimates, worldwide there are now around 1.4 billion people aged 30 to 79 with a diagnosis of hypertension: a condition in which resting blood pressure is higher than threshold values considered normal. Having hypertension means living with a major risk factor for several potentially fatal cerebrovascular and cardiovascular diseases.

But what are the threshold values beyond which a person is defined as “hypertensive”? The answer is that there is no single answer: it depends on which guidelines are used as a reference. However, one thing is constant: over the decades, the threshold values have steadily been lowered to the point of reaching, in some cases, parameters that until recently were considered normal.

This is shown by an analysis led by researchers from the University of Bologna and published in the journal Medical Sciences. The study – the first worldwide on this topic – considered 32 clinical practice guidelines developed by national and international bodies and institutions: from the World Health Organization to the European Society of Cardiology, including the International Society of Hypertension and the United Kingdom’s National Institute for Health and Care Excellence.

The study began in the 1970s, when to be defined as “hypertensive” a person had to have values above 160 systolic pressure (or “maximum pressure”) over 95 diastolic pressure (or “minimum pressure”). However, this threshold was progressively lowered, until the latest European and American guidelines, published this year, according to which it is possible to be hypertensive even with a pressure of 120 over 80: values that until recently were considered optimal.

"Given that average maximum pressure for people over fifty in Italy is around 130, this means that a huge number of Italians would be considered hypertensive, with all that this entails in terms of lifestyle changes and any treatment", explains Lamberto Manzoli, Professor in the Department of Medical and Surgical Sciences - DIMEC at the University of Bologna, who coordinated the study. "The issue is particularly delicate, both because of the major economic interests at stake and because other guidelines, such as the English ones and those of the World Health Organization, have instead kept the thresholds unchanged at 140 over 90".

The researchers’ analysis showed that, over the decades, all national and international scientific societies have changed their definition of “hypertension”, lowering the threshold values that lead to the diagnosis of this condition and therefore to the start of therapeutic treatments to reduce blood pressure.

On the one hand, this approach is designed to extend the benefits of treatment to patients for whom hypertension is still at an early stage: a way to keep the situation under control more easily and prevent the condition from becoming critical. On the other hand, however, a much larger number of patients becoming eligible for drug therapy or more intensive treatment regimens inevitably leads to an increase in the overall costs of managing hypertension. This is also due to the fact that the number of people who are unable to achieve what are considered optimal blood pressure levels is on the rise.

"Lowering the threshold values not only results in millions of people being reclassified as unwell rather than healthy, but also means that a huge number of patients already undergoing treatment are no longer able to meet the new, lower blood pressure targets and therefore require higher doses of medication”, confirms Lamberto Manzoli. "These patients are therefore destined to remain in the category of a ‘person at risk’, with no hope of returning to “normal”, along with all the stress that this entails and the implications for their lifestyles".

The fact that various national and international guidelines indicate different blood pressure threshold values for the diagnosis of hypertension – the researchers conclude – causes uncertainty among doctors when they have to decide whether or not a patient needs to start a course of treatment. This uncertainty is also growing because of the tendency for people to look online for information, answers and advice on medical matters.

The study was published in the journal Medical Sciences with the title “The Evolution of Blood Pressure Thresholds and Targets over Time: A Historical Review”. For the University of Bologna, Cecilia Acuti Martellucci, Claudio Borghi and Lamberto Manzoli took part, all from the Department of Medical and Surgical Sciences - DIMEC. The other authors are: Gabriele Brunini, Matteo Fiore, Maria Elena Flacco, Flavia Minoia, Martina Rosticci and Giancarlo Cicolini.