MORE than two-thirds of Australian adults with blood pressure higher than the national guidelines are unaware that they have hypertension, say experts.
Professor Markus Schlaich, who holds the Dobney Chair in Clinical Research at the University of Western Australia and was a member of National Heart Foundation Hypertension Guidelines Committee, said that discussions about the exact threshold for hypertension diagnosis were “academic”, and the more crucial issue was the high proportion of people who were not aware of their hypertensive status.
“A key aspect is that a lot of people who have blood pressure of about 140/90 do not know about it,” Professor Schlaich said. Recent research found that 71% of Australian adults with blood pressure above 140/90 mmHg were unaware that they had hypertension.
Professor Schlaich said that the focus should be on increasing the awareness of hypertension and its potential consequences in the community.
“We need campaigns to increase understanding that blood pressure – among other things such as overweight and high cholesterol – is an important factor in cardiovascular risk. People should know what their levels are and that there are simple things that can be done to reduce this risk, such as adopting a healthy lifestyle.”
Professor Schlaich was commenting on a Perspective published in the MJA which pointed out that the number of adults diagnosed with hypertension would double if Australia was to follow the US lead in lowering the blood pressure threshold for diagnosis.
Professor Garry Jennings, Executive Director of Sydney Health Partners, and co-authors wrote that Australia would stand by its 2016 Australian guidelines, published by the National Heart Foundation, and its definition of hypertension in the general population of 140/90 mmHg, despite US moves to change its definition.
In late 2017, the American College of Cardiology (ACC) and the American Heart Association (AHA) published new guidelines that lowered the threshold at which hypertension was diagnosed from 140/90 mmHg to 130/80 mmHg. The change was made on the basis of epidemiological evidence – particularly the 2015 Systolic Blood Pressure Intervention Trial (SPRINT). The SPRINT study found that among patients at high risk of cardiovascular events, but without diabetes, a systolic blood pressure of 120 mmHg was associated with lower rates of major cardiovascular events and all-cause mortality than a systolic blood pressure of 140 mmHg.
The MJA authors wrote that adopting the ACC/AHA guidelines throughout Australia would double the proportion of adults classified as having hypertension.
“That is, of the 18 million individuals aged 20 years and over, the health status of 4.5 million would change,” the authors wrote. “It would increase the proportion of adults recommended for antihypertensive therapy based on blood pressure readings in the general population.”
The MJA authors noted that the American Academy of Family Physicians had not endorsed the new US guidelines.
Professor Schlaich said that the Australian committee thoroughly reviewed the evidence, including the findings from the SPRINT study, in developing the local guidelines.
“While we stuck with the 140/90 mmHg threshold, we do make recommendations that in certain [high risk] populations, such as those in the SPRINT trial, it may be worthwhile to look at lower blood pressure levels,” Professor Schlaich told MJA InSight. “But we did not feel there was sufficient evidence yet to bring the general definition of hypertension to a level the Americans have done.”
Professor Schlaich added that there would be economic implications to changing the definition in Australia.
“If you diagnose somebody with elevated blood pressure, then you have to implement therapeutic strategies,” he said. “Lifestyle [modifications don’t] cost the system anything, but medication would sometimes be required, and then there was the issue of whether patients actually take their medication.”
The MJA authors wrote that medication non-adherence was a particular issue among younger patients, many of whom would become eligible for drug therapy under the new US guidelines.
In an MJA InSight podcast, lead author of the MJA article, Professor Jennings, who is also Chief Medical Adviser to the Heart Foundation, agreed that more needed to be done in Australia to increase awareness of hypertension.
“It’s the highest risk factor driving cardiovascular disease. It accounts for about a third of the cardiovascular disease in the community, and yet people just don’t understand that,” said Professor Jennings, who is senior director of the Baker Heart and Diabetes Institute.
“There’s a sense that high blood pressure is just another condition that you take some pills for because the doctor told you to, and it may or may not be important down the track.”
Commenting on the article, Professor Carl Lavie, Professor of Medicine at Ochsner Clinical School, University of Queensland, said that it made several important points.
“The [MJA authors] make a good case that even with the old guidelines in the US and the less stringent Australian guidelines, many are not aware of their hypertension, and they are not being optimally treated to below 140/90 much less lowering the goals further,” Professor Lavie said.
“Obviously, getting more people below 140/90 would be more important than lowering the goal further, but I suspect that many in Australia with known [atherosclerotic cardiovascular disease] or who have high risk based on their other risk factors would have lower risk if their blood pressure was less than 130/80, than just 140/90.”
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