Author: Dr Patrick Gladding
Hypertension is the world’s most common modifiable risk factor for cardiovascular disease and death. Globally, it is estimated that more than one billion adults have hypertension, and this number could reach one-and-half billion by 2025. Given that hypertension has no symptoms but accounts for over nine million deaths annually, it is known as the “silent killer”.
However, managing hypertension is not easy. Treating patients according to guidelines can be both confusing and at odds with ‘other evidence’ or ‘treatment options’. Here Cardiologist, Dr. Patrick Gladding, opens the books on hypertension, sharing his thoughts and views on why doctors – and patients they treat – should take guidelines with a grain of salt.
Guidelines don’t always apply to the individual patient, says Dr Gladding, and this issue was especially highlighted in the New England Journal which featured results from a Prospective Urban Rural Epidemiology (PURE) study published in 2014.
The study involved taking morning fasting urine samples from 101 945 people in 17 high and middle income countries – patients were followed up for an average of 3.7years. PURE findings revealed that higher than estimated sodium excretion (≥7grams a day) were associated with an increased risk of death or major cardiovascular event – odds ratio 1.15 – compared with the reference range. This association was strongest in patients with hypertension, however, patients with an estimated sodium excretion of less than 3grams a day were also found to have a higher risk of death or major cardiovascular event – odds ratio 1.27 – than those in the reference range.
What did the evidence show us? That a lack of salt in the diet can increase the risk of a major cardiovascular event and death, just as consuming too much salt can also. Confused? You’re not alone, says Dr. Gladding.
“Looking at American guidelines, they recommended salt intake to roughly between 2.20-2.60grams per day, and it has now been documented that there is a J-shape curve to salt intake, so actually where they set their threshold was too low – if you adhered to that – you increased the risk of cardiovascular events, particularly stroke, at a greater increment than it would be if you took more salt,” explains Dr Gladding. “So, it really is confusing. Similarly most recent American Hypertension guidelines have stated that previously we might have been a bit overzealous treating everybody – maybe when you are older and your arteries are stiff, and it’s harder to get your blood pressure down, you shouldn’t aim for such low numbers – so if you were treating a person over 60 you might accept a BP up to 150/90, before starting treatment.”
As the New York times has reported in recent years, blood pressure is indeed a ‘mystery number’, says Gladding – no one is really sure what is the best number to treat, or the number to treat to.
However, a focus on treating a patients biological age, not years alone, could be a good guide to follow when treating blood pressure in the elderly, says Gladding – citing recent data from Longitudinal Aging Study Amsterdam (LASA).
Analysis of findings presented at European Society of Hypertension conference in 2014, called for physicians to consider ‘biological’ age over ‘chronological’ age when managing blood pressure in the elderly. In the population as a whole, systolic blood pressure (SBP) had no relationship with mortality risk. By contrast, both high and low DBP were linked to increased mortality.
“This was a fairly sizeable study – 1466 patients – findings showed that if you are overweight and elderly, a high diastolic blood pressure of more than 90 was associated with a 50% increase in mortality,” explains Dr. Gladding. “But by contrast, if you are frail and elderly, a low diastolic blood pressure was associated with a 50% increase risk of dying during the 15-year follow-up.”
We need more information about the balance of risks and benefits when treating patients, not just a reliance on trial evidence as the recent SPRINT study would encourage many of us to do, says Dr. Gladding.
The SPRINT study
“SPRINT was published at the end of 2016 and it was a very large study,” explains Dr. Gladding. “It posed the question: How low should blood pressure go? And answered it with: much lower.”
SPRINT, randomly assigned more than 9,300 men and women ages 50 and over, with a range of blood pressures from 130 to 180, who were at high risk of heart disease or had kidney disease, to of two systolic blood pressure targets: less than 120 millimetres of mercury, which is lower than any guideline ever suggested, or less than 140.
“The composite end point occurred in 5.2% of the intensive group versus 6.8% of the standard treatment group,” says Dr. Gladding. “As a result of this you did have some people saying lower blood pressure is a life saver and we need to treat blood pressures right down to the lowest level possible, but that just doesn’t work – it can’t.”
Gladding believes treatment really does need to be more personalised.
“A respected epidemiologist and cardiologist from Yale said these things about the SPRINT trial. Firstly, the results should not be considered a mandate for people to run out and get blood pressures below 120 – really only one-in-five patients you’ll see would have fitted into that trial anyway. Secondly, the potential benefits of lowering blood pressure must be weighed against the harms – particularly in the frail and elderly,” says Dr. Gladding. “Thirdly, we need more information about the balance of risks and benefits so each patient can have their choice personalised.”
As a result of discussions like this the investigators from the SPRINT trial released all the individual patient data from the trial onto the internet and proposed a competition, to see who could generate the best algorithm to individualise the intensiveness of antihypertensive treatment. Within only a few months over 160 contestants had entered and 3 were awarded prizes for their work. One of these algorithms has now been built into an app, which in the near future we will be able to use to truly personalise treatment for each of our patients.