The false sense of confidence about blood pressure means that the public does less medical monitoring to control it, which could potentially put their health at risk. This is one of the main conclusions of research led by the University of Southern California (USC), with the participation of researchers linked to UPF and universities and research centres in Leeds, Pittsburgh, St. Louis and Sydney.

The main results of the study are the focus of the article “The Role of Confidence and Knowledge in Intentions to (Not) Seek Care for Hypertension: Evidence From a National Survey”, published on 25 January in the journal Medical Decision Making and drafted by Wändi Bruine de Bruin (Price School of Public Policy and Dornsife Department of Psychology, University of Southern California, Los Angeles), Yasmina Okan (UPF Department of Communication and Centre for Decision Research, Leeds University Business School), Tamar Krishnamurti (Center for Research on Health Care, Division of General Internal Medicine, University of Pittsburgh), and Mark D. Huffman (Global Health Center and Cardiovascular Division, Washington University in St Louis and The George Institute for Global Health, Sydney).

Yasmina Okan (UPF) “It is important not to let ourselves be guided solely by our subjective confidence, to inform ourselves about the meaning of different blood pressure values from reliable sources and to seek medical attention if our levels are high”.

Based on the study conclusions, Yasmina Okan, co-author of the article linked to the UPF Department of Communication, explains: “confidence may not correspond to our objective knowledge, especially if we have never been given clear explanations about blood pressure targets and the implications of different levels of systolic and diastolic pressure. It is important not to let ourselves be guided solely by our subjective confidence, to inform ourselves about the meaning of different blood pressure values from reliable sources and to seek medical attention if our levels are high”.

What do blood pressure numbers mean?

Blood pressure values are measured using two numbers. The upper number corresponds to the systolic blood pressure and measures the pressure in the arteries when our heart beats. The second number corresponds to diastolic blood pressure and measures the pressure in the arteries when our heart rests. According to the American Heart Association, there are five categories of blood pressure, on which the study conducted in the United States is been based, with the following values:

• Normal (systolic pressure less than 120 mm Hg and diastolic less than 80 mm Hg)
• High (systolic pressure between 120-129 mm Hg and diastolic less than 80 mm Hg)
• Grade 1 hypertension (systolic pressure between 130-139 mm Hg or diastolic between 80-89 mm Hg)
• Grade 2 hypertension (systolic pressure greater than 140 mm Hg or diastolic pressure greater than 90 mm Hg)
• Hypertensive crisis: systolic pressure greater than 180 mm Hg and/or diastolic pressure greater than 120 mm Hg

In Europe, the blood pressure categories established by the European Society of Cardiology and the European Society of Hypertension vary slightly from those set out in the American guidelines. In the European context, the defining threshold for hypertension would be 140/90 mm Hg, while values below 130/85 mm Hg would be categorized as normal.

To assess the level of public knowledge about blood pressure according to the criteria of the American Heart Association, the research group that authored the study commissioned a survey of 6,592 American adults, including 1,342 with hypertension without comorbidities (heart disease, kidney disease or diabetes) and 795 with hypertension and comorbidities. The survey was conducted through the Understanding America Study of the USC Center for Economic and Social Research (CESR). The research has received financial support from the following institutions: Roybal Center for Behavioral Interventions in Aging from the National Institute on Aging, CESR and USC Schaeffer Center for Health Policy & Economics.

Bruine de Bruin, principal investigator of the study (University of Southern California): “We tend to feel more confident about issues that are more familiar. And blood pressure feels like a familiar issue because it’s taken at almost every medical visit”

64% of respondents expressed confidence in their understanding of blood pressure numbers, but only 36% stated that 120/80 mm Hg was the maximum threshold for normal/healthy blood pressure. This percentage reached 39% when a broader criterion was used that considers the maximum threshold to be 130/80mm Hg. Among the causes of false confidence about one’s own knowledge of blood pressure, the study cites that it is a topic that is familiar to many people. “We tend to feel more confident about issues that are more familiar. And blood pressure feels like a familiar topic because it’s taken at almost every medical visit”, says Bruine de Bruin, author and principal investigator of the paper and co-director of the Behavioral Sciences Program at the USC Schaeffer Center for Health Policy & Economics.

Health risks of insufficient blood pressure control

In the long term, high blood pressure damages blood vessels, increases the risk of heart failure and leads to other health problems, especially in patients with additional diseases such as heart disease, kidney disease and diabetes. High blood pressure is more common as we age and most people will develop it during their lifetime. One of the factors that makes it difficult to diagnose is that high blood pressure “usually has no symptoms”, as Bruine de Bruin (University of Southern California) warns. Hence, the co-author of the paper and expert on high blood pressure Mark Huffman, a professor of Medicine at the University of Washington in St. Louis, assures: “Identifying, treating and managing high blood pressure is a major clinical and public health challenge”.

In the United States, where this study has been conducted, almost half of the adult population has hypertension according to data from the Centers for Disease Control and Prevention. In our immediate environment, the incidence of hypertension is also high. In Spain, it is estimated that between 33% and 44% of the population has hypertension, according to data from several studies. In addition, it is estimated that more than a third of patients with hypertension in Spain have not been diagnosed. Regarding the level of knowledge of the Spanish population about blood pressure, Yasmina Okan (UPF) explains: “Existing studies in Spain indicate that the level of knowledge is low in general, even among patients with hypertension. However, as far as we have managed to determine, the aforementioned studies have not analysed the relationship between people’s level of knowledge on this subject and their confidence”.

Yasmina Okan (UPF): “the media undoubtedly play a critical role, as the level of media coverage can affect our perception of the risk associated with hypertension. Today, despite being one of the leading causes of death globally, hypertension does not usually receive much media attention”

What is common in all Western societies is the high incidence of high blood pressure. According to the WHO, it is one of the most frequent health problems in modern societies and affects 1.13 billion people worldwide. For this reason, the study highlights the need to develop more actions to raise awareness and prevent high blood pressure. On the one hand, campaigns by health authorities and the information provided directly by health professionals to their patients could contribute to improving the level of knowledge about blood pressure among citizens. Currently, “the knowledge of what these blood pressure numbers mean is not transferred from the professional to the patient”, Bruine de Bruin (USC) assures. On the other hand, Okan (UPF) highlights the role that the media can play: “the media undoubtedly play a critical role, as the level of media coverage can affect our perception of the risk associated with hypertension. Today, despite being one of the leading causes of death globally, hypertension does not usually receive much media attention”. In short, she believes that the media could contribute further to preventing high blood pressure and its consequences.