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Blood pressure treatment is beneficial for most people with high blood pressure. A recent study suggests that this may not always be the case for the elderly.
High blood pressure, also called hypertension, is one of the most important risk factors for stroke and heart disease. It is also very common, affecting a quarter of Canadian adults and a third of American adults. There are several behavioural changes that can lower blood pressure, such as eating a healthier diet or getting more exercise. There are also drugs that can lower blood pressure. Doctors will usually prescribe these drugs once systolic blood pressure passes above 160 mmHg. Systolic blood pressure is the pressure when the heart is contracting and pushing blood most forcefully. A systolic blood pressure of 120 mmHg is ideal.
There is evidence that blood pressure treatment can reduce the risk of death and disease in patients with high blood pressure. However, many of the scientific studies that proved this did not include participants who were very ill or frail. This means that older adults, who are more likely to be ill or frail, were often excluded from these studies.
It is therefore possible that blood pressure treatment may not help the oldest old. In fact, some small, short-term studies have even hinted that lower blood pressure and blood pressure treatment is actually associated with an increased risk of death and cognitive decline in most elderly patients.
Because of this uncertainty, researchers in the Netherlands set up a study to address this issue. Their study investigated the effects of blood pressure treatment on mortality and cognitive function in adults older than 85 years. The results of their research were recently published in the scientific journal Age and Ageing.
A large study of the oldest senior adults
The researchers tried to include everyone in the city of Leiden, in the Netherlands, who turned 85 over a specified two-year period. A total of 570 people consented to be included in the study. Almost a fifth of participants were in a hospital or care facility due to illness.
At the start of the study, the research team visited all the 85-year-old participants to measure their blood pressure. They also tested their cognitive function to find out if they had dementia. At the same time, they measured grip strength, tested for depression, and recorded information on socioeconomic status and whether or not the participant smoked.
The study lasted five years. Every year, the participants were re-tested for cognitive function and dementia.
Participants receiving blood pressure treatment were more likely to have cardiovascular disease
At the start of the study, 44% of the participants were receiving drugs for blood pressure treatment. The researchers compared those receiving blood pressure drugs to those who were not. Study participants who were being treated for high blood pressure were more likely to have a history of cardiovascular disease compared to those not being treated. However, there were no differences in cognitive function, or in any other category, between the two groups.
Surprisingly, there was no difference in average blood pressure between the two groups. Both groups had average systolic blood pressures of 155 mmHg. This could mean that the drugs had successfully lowered blood pressure in the treatment group. Alternatively, it could mean that doctors were looking at other factors beyond blood pressure when they prescribed these drugs.
More deaths in treated participants with lower blood pressure
The researchers kept track of how many participants died over the five years of the study. Because these participants were older to begin with, almost half of the participants died. Blood pressure did not affect mortality rates in the group of participants who were not being treated for high blood pressure. However, this wasn’t true for participants being treated for high blood pressure. In this group, those with lower blood pressure were actually more likely to die compared to those with higher blood pressure.
Surprisingly, the least likely to die were those receiving drug therapy with a blood pressure greater than 170 mmHg. In fact, treated participants were 1.3 times more likely to die with every 10 mmHg decrease in blood pressure. For example, a participant with a blood pressure of 150 mmHg was 1.3 times more likely to die than a participant with a blood pressure of 160 mmHg. This effect was not observed in the group of participants who were not being treated for high blood pressure.
Faster cognitive decline in treated participants with lower blood pressure
There was no relationship between blood pressure and cognitive decline in untreated participants. However, blood pressure did seem to matter in participants being treated for high blood pressure. In this group, those with the lowest blood pressure tended to show a faster cognitive decline compared to those with the highest blood pressure. Participants with lower grip strength at the start of the study saw even faster declines in cognitive function.
A concerning finding
This study implies that the health benefits of low blood pressure do not apply to older elderly adults. In fact, it suggests that blood pressure treatment could actually be harmful in these patients. However, this was only an observational study, and therefore could not conclusively prove that blood pressure treatment should be avoided in the elderly. For proof, researchers would need to set up a clinical trial, where study participants are randomly assigned to either blood pressure medication or a placebo.
Despite this limitation, this study is obviously concerning for doctors who must decide if they should treat their elderly patients for high blood pressure. The researchers do not offer any advice, but they do point to another recent study that investigated the effect of taking older patients off of their blood pressure medication. That short, four-month, study found no harmful effect of temporarily stopping blood pressure treatment. The researchers concluded that more studies are needed to address this question.
Written by Bryan Hughes, PhD
- Streit, S., Poortvliet, R. K. E. & Gussekloo, J. Lower blood pressure during antihypertensive treatment is associated with higher all-cause mortality and accelerated cognitive decline in the oldest-old. Data from the Leiden 85-plus Study. Age and Ageing 47, 545-550 (2018)
- Nerenberg, K. A., Zarnke, K. B., Leung, A. A., et al. Hypertension Canada’s 2018 Guidelines for Diagnosis, Risk Assessment, Prevention, and Treatment of Hypertension in Adults and Children. Canadian Journal of Cardiology 34, 506-525 (2018). https://www.onlinecjc.ca/article/S0828-282X(18)30183-1/fulltext