The idea that treating high blood pressure can sometimes do more harm than good has gained further support from a study of people over the age of 75 with the condition.
This is because, contrary to expectations, people in this group who had high blood pressure had a lower risk of death than those with lower blood pressure. “Overall, blood pressure treatment is a good thing, but there are likely to be people in whom the risks outweigh the benefit,” says Jane Masoli at the University of Exeter, UK.
Over the past few decades, the level at which blood pressure, which is measured in millimetres of mercury (mmHg), is classed as too high and needing treatment has fallen. Doctors used to recommend treatment to reduce blood pressure when it was more than 200/100 mmHg.
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Now the optimal blood pressure level is generally seen as between 120/80 and 90/60 mmHg. UK guidelines recommend treating someone over the age of 80 if their blood pressure is over 150/90 mmHg, and over 140/90 mmHg in people who are younger. In the US, the target has recently been lowered to 130/80 for all ages.
Blood pressure varies over time and the medications that lower it can also If these medicines lower blood pressure too much, this can cause dizziness and falls, which can be dangerous for older people.
Masoli’s team looked at people who are more vulnerable to such harms but who are usually excluded from trials of blood pressure medicines: people who are 75 years old or more, and those who are frail or who have multiple health problems.
The group tracked the health of about 400,000 people in the UK for 10 years. All participants were at least 75 years old when the study began. While those with a blood pressure above 150 mmHg had a higher rate of heart attacks and strokes than people whose blood pressure was lower during the study period, there were fewer deaths in that group overall.
In people who were aged between 75 and 84 years old at the start of the study, the lowest risk of death from any cause was in those whose systolic blood pressure was between 140 and 170 mmHg – which would usually be classed as too high. And in those over 85, having blood pressure over 140 mmHg always carried a lower risk of death, no matter how high their blood pressure was.
The study cannot directly ascribe any deaths to medication because it didn’t look at what drugs people were taking. But Masoli says that because previous studies have found that very low blood pressure is associated with worse outcomes, “we should be cautious in all people who have lower blood pressure in older age, whether treated or not”.
The study also raises questions about whether mildly raised blood pressure needs treating, especially in the oldest and frailest individuals, says Masoli. “Older people who are frail are likely to be different to those in the studies that we are basing guidelines on.”
As well as the drugs having side effects, it can be burdensome to take lots of tablets every day, says Masoli. People may need to take two or three different medicines to get their blood pressure down to the target level, on top of those they make take for other conditions such as diabetes or arthritis. “Some may be on 10 different medications,” she says.
However, no one should stop taking blood pressure medication without discussing it with their doctor, says Masoli. “People are on this to reduce their cardiovascular risk.”
“We need to be aware that blood pressure treatments in the elderly can be associated with harm,” says James McCormack at the University of British Columbia in Canada. “There needs to be that balance between benefits and harm.”
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