Hypertension is one of the most important risk factors for cardiovascular morbidity and mortality worldwide. According to the Robert Koch Institute, around 9.4 million deaths worldwide each year are attributable to hypertension. In addition, about a quarter of the world's population has high blood pressure. Early detection and treatment of this condition is crucial to avoid complications. However, high blood pressure often goes undetected. But even when the condition is noticed, not every patient receives appropriate treatment.
For this reason, the Assistant Professorship of Public Health and Prevention headed by Prof. Dr. Michael Laxy conducted a study to investigate the impact of population-based blood pressure screening and subsequent low-threshold informational treatment on long-term cardiovascular disease morbidity and mortality. The results have now been published in the journal "PLOS Medicine" under the title "The effect of population-based blood pressure screening on long-term cardiometabolic morbidity and mortality in Germany: A regression discontinuity analysis." The journal has an impact factor of 11.069.
The study refers to results from four waves of the study "Cooperative Health Research in the Augsburg Region" (KORA) between 1984 and 1996. The KORA study is a research platform of Helmholtz Center Munich to investigate the relationships between health, disease and the living conditions of the population. The KORA cohort, consisting of approximately 18,000 participants, represents a population-based random sample of all 25- to 74-year-olds in the Augsburg area.
For the main analysis, data from a total of 14,592 individuals were considered. This involved investigating whether a simple message in the form of a letter to individuals diagnosed with hypertension in the KORA study led to a lower risk of stroke, myocardial infarction, and other forms of heart disease or to lifestyle changes. The purpose of this letter was to motivate these individuals to visit their primary care physician to discuss hypertension. The presence of hypertension, and thus the communication of the appropriate information, was based on the classic hypertension threshold of 140/90 mmHg.
"The idea was that if patients were diagnosed with hypertension in the KORA study, they would receive the results by letter and, based on that, go to the doctor to start therapy," explained Dr. Sara Pedron, first author and Research Associate at the Assistant Professorship of Public Health and Prevention. "We asked ourselves what effect this form of communication had on the patients. We can see that now that we've extracted and analyzed data on the behaviors, cardiovascular events and deaths of people who have been in the study for 30 years."
A regression-discontinuity analysis was used to evaluate whether the information in the form of a letter that participants received had an effect on morbidity and mortality rates over the nearly 17-year period following the study. To do this, the results were compared with those of individuals with similar blood pressure who were directly below a hypertension threshold and therefore had not received the information.
"The regression-discontinuity design is a relatively innovative public health or epidemiology technique that mimics a kind of randomized experiment," Prof. Laxy explains. "In the design, which is one of the quasi-experimental procedures, it takes advantage of the fact that the subjects are almost identical above or below the hypertension threshold, but one group receives the intervention in the form of the letter compared to the other. It is therefore a very efficient method to estimate the causal effect of interventions from such a screening with observational data. This type of analysis is becoming more common in the health sciences. However, there is still a lot of untapped potential."
The study's findings suggest that simply informing patients about their hypertension status is not enough to affect long-term cardiovascular health. "We did not find a difference between the two groups," Dr. Pedron said. "But that doesn't automatically mean there was no difference. The reason for this is wide confidence intervals."
In addition, an attempt was made to map the causal chain using existing data. To do this, potential intermediate outcomes such as systolic and diastolic blood pressure, hypertension awareness, physical activity, smoking and body mass index were examined in 5,085 subjects using data from two follow-up studies after seven years. "However, we did not find any differences here either," the Research Associate explains.
The study thus provides no evidence of an effect of assessed blood pressure screening and subsequent informational treatment on blood pressure and behavior. The intervention also had no effect on long-term cardiovascular disease mortality and morbidity. "We did this study with the ulterior motive that this was a very low-cost intervention that could be scaled up with little effort and cost if it had any effect. Even if we had only seen a very small effect, that would have been very interesting. On the other hand, we knew that the information using the letter was a low-threshold intervention. We examined the data anyway because, to our knowledge, there are very few studies with which to examine such an intervention. However, the fact that the intervention did not work as hoped is of course also an interesting result," Dr. Pedron summarizes the results of the study.
To the publication "The effect of population-based blood pressure screening on long-term cardiometabolic morbidity and mortality in Germany: A regression discontinuity analysis” in the journal “PLOS Medicine”
To the homepage of the Assistant Professorship of Public Health and Prävention
Contact:
Prof. Dr. Michael Laxy
Assistant Professorship of Public Health and Prevention
Georg-Brauchle-Ring 60/62
80992 München
phone: 089 289 24977
e-mail: michael.laxy(at)tum.de
Dr. Sara Pedron
Assistant Professorship of Public Health and Prevention
Georg-Brauchle-Ring 60/62
80992 München
e-mail: sara.pedron(at)tum.de
Text: Romy Schwaiger
Photos: „PLOS Medicine“/private