Impact of Lower BP Cutoffs to Define Hypertension Varies Globally
Low-income countries—least equipped to handle an influx of new patients—would see the biggest increases with lower thresholds.
If the blood pressure threshold used to define hypertension is lowered, the increase in the population of patients with the condition would not be consistent across the world, a study shows.
According to an analysis of more than 4 million people who had their BP measured, relative and absolute increases in the hypertensive population would be greatest in lower-income nations and younger age groups, researchers led by Janis Nolde, MD (Dobney Hypertension Centre, University of Western Australia, Perth), report.
“While focusing on lower BP targets may constitute an opportunity for early intervention, the potential socioeconomic consequences may pose unsurmountable obstacles for most healthcare systems worldwide,” they write in a study published online in Hypertension last week to coincide with World Hypertension Day, adding that moves to define hypertension at lower cutoffs “require thorough preparation of the healthcare systems responsible for delivery.”
Over the years, as data showing that lowering BP reduces cardiovascular events has accumulated, BP thresholds for defining hypertension have fallen. The SPRINT trial, with results released in 2015, has contributed to that trend, showing that in nondiabetic patients with hypertension and a high cardiovascular risk, treating to a systolic BP goal of less than 120 mm Hg versus a goal of less than 140 mm Hg reduced adverse clinical outcomes. Those findings were a major driver of the lower BP thresholds used to define hypertension (systolic 130 to 139 mm Hg or diastolic 80 to 89 mm Hg for stage 1) in the comprehensive US guidelines published in 2017.
But not all guidelines are in agreement, and those from the European Society of Cardiology/European Society of Hypertension, the World Health Organization, and the International Society of Hypertension (ISH) maintain a higher cutoff of 140/90 mm Hg.
A Broader Look
Though some prior studies have explored the impact of lowering the BP thresholds to define hypertension, none has had as a broad a scope as the current one. Nolde and colleagues examined data on more than 4.02 million people participating in the May Measurement Month initiative, an annual screening campaign started by the ISH, between 2017 and 2019 across 104 countries.
Using a BP threshold of 140/90 mm Hg or greater, 33.5% of participants would be classified as hypertensive. Implementing the definition from the US guideline, with a cutoff of 130/80 mm Hg or greater, would boost that proportion to 56.1%. And dropping the threshold even further, to 120/70 mm Hg or higher, would place 83.5% of participants in the hypertensive category.
The issue here is the magnitude of this increase. Tazeen Jafar
After standardizing for age and sex, the median relative increase in the rate of hypertension would be 72.3% when lowering the threshold from 140/90 mm Hg to 130/80 mm Hg and 162.6% when dropping it to the lowest cutoff.
The changes were most dramatic in low-income countries and least pronounced in high-income countries. For example, the largest relative increase in the rate of hypertension when lowering the cutoff from 140/90 mm Hg to 130/80 mm Hg was seen in Southeast Asia (91.4%), whereas the smallest increases were observed in Europe (43.9%) and the Americas (45.4%).
Regardless of the definition employed, men were more likely to be hypertensive than women. Of note, the average age of the hypertensive population was lowest when the threshold of 120/70 mm Hg was used (46.9 years), increasing with higher cutoffs (49.7 years for 130/80 mm Hg and 53.8 years for 140/90 mm Hg).
In discussing the implications of the findings, the researchers note that hypertension by any definition is undertreated and poorly controlled across the world.
“Whether decreasing the threshold of hypertension further is a more-suitable strategy to combat cardiovascular disease than focusing on awareness and optimizing treatment in those already classified as hypertensive is uncertain,” they say. “Robust and comparable data on the treatment status of hypertensive populations in different regions are required for a sensible, informed decision-making process for the development of local and global guidelines.”
Moreover, the changes in patient characteristics seen when hypertension is defined differently “requires careful assessment, as the demographic shift that comes with these changes may have a major impact on the burden healthcare systems are exposed to,” Nolde and colleagues write, noting that low-income countries may have the greatest difficulty in managing a suddenly larger hypertensive population.
‘Very Alarming Findings’
Commenting for TCTMD, Tazeen Jafar, MBBS (Duke-NUS Medical School, Singapore), who served as guest editor for the paper, said it’s not surprising that lowering the BP threshold will boost the number of patients with hypertension. “The issue here is the magnitude of this increase,” particularly in the younger population and in low- and middle-income countries, she said.
“These are very alarming findings,” Jafar stressed.
As also highlighted by the researchers, Jafar underscored that hypertension control is poor across the world even at a standard threshold of 140/90 mm Hg. She added that over the last 5 years or so, the long-term gains that have been achieved in the United States and elsewhere have stalled or even reversed as age-standardized BP levels have risen.
This is particularly concerning for people living in low- and middle-income countries, who already have enhanced susceptibility to cardiometabolic conditions due to living in poverty and struggle with the burdens of infections, high rates of maternal mortality, and other health risks, Jafar said. In those parts of the world, healthcare systems face challenges in providing patients with the care they need, including essential antihypertensive medications.
“The implications of lack of prevention are much more serious for a low- and middle-income country than it is for a high-income country” when considering economic, social, and individual factors, she said. “This is a very complex situation, and it needs to be addressed by health promotion, by policy-level changes.” Population-level interventions that have proven successful at a local or regional level, like those tested in the HOPE 4 study, the China Rural Hypertension Control Project, and the COBRA-BPS trial (which she led), need to be scaled up, Jafar said.
Asked whether it’s worth discussing lower thresholds for defining hypertension when control at higher cutoffs is so poor, Jafar acknowledged that 140/90 mm Hg is an important goal but added that research has shown that cardiovascular risk reduction is enhanced if BP is brought even lower. That doesn’t necessarily mean that greater use of antihypertensive medication is warranted, she said. “What it means is that we [need to] start thinking about what else can we do at a population level,” including lifestyle modification.
“This is the time to be thinking about why are these interventions not being rolled out,” Jafar said about proven population-level efforts to address high blood pressure. “Maybe the funders who are continually thinking about infectious diseases need to turn their attention to hypertension and noncommunicable diseases.”
Nolde JM, Beaney T, Carnagarin R, et al. Global impact of different blood pressure thresholds in 4,021,690 participants of the May Measurement Month initiative. Hypertension. 2022;Epub ahead of print.
- The study was supported by resources provided by the Pawsey Supercomputing Centre with funding from the Australian Government and the Government of Western Australia. This research also was supported by the International Society of Hypertension, Servier, and Omron Healthcare.
- Jafar and Nolde and report no relevant conflicts of interest.