Intensive blood pressure treatment might improve blood flow in the brain
Results from the SPRINT MIND trial show that rather than impairing blood flow, a lower blood pressure target might improve it
Intensive blood pressure treatment might improve blood flow in the brain
Results from the SPRINT MIND trial show that rather than impairing blood flow, a lower blood pressure target might improve it
A recent analysis of data from the SPRINT MIND trial has shown that lowering blood pressure to a target of 120mmHg rather than 140mmHg does not reduce blood flow in the brain. In fact, it appears to improve it, especially in people with existing cardiovascular disease (diseases of the heart and blood vessels). The results, published this March, suggest that more intensive blood pressure treatment is safe in terms of blood flow, countering fears that it could cause a lack of blood to the tissues of the brain.
Why was the study done?
High blood pressure is a major risk factor for diseases of the brain and blood vessels (cerebrovascular disease) including stroke, small vessel disease and dementia. Treatment to lower blood pressure is key in lowering the risk of diseases of the heart as well as the brain, but there is uncertainty about how far to lower it and worries that lowering it too far could cause ‘hypoperfusion’ – a lack of blood flow to the brain that leads to small vessel disease and contributes to cognitive decline.
What is the SPRINT trial?
2016’s Systolic Blood Pressure Intervention Trial (known as the SPRINT trial) was a landmark trial that showed intensive treatment to lower systolic blood pressure (the top number) down to below 120mmHg rather than the standard 140mmHg reduced the risk of stroke. It also showed other benefits for brain health, including fewer cases of cognitive impairment. The effect was so clear that the trial was stopped early, and the results have influenced blood pressure management and treatment guidelines.
What did the current study involve?
The current findings are part of SPRINT MIND, a sub-study of the SPRINT trial. The analysis included 315 adults aged 67 on average with raised blood pressure and at least one risk factor for diseases of the heart and blood vessels. They were split into two groups with a target blood pressure of either 140mmHg or 120mmHg, and had MRI scans of their brains at the start of the trial and again four years later.
What did the results show?
As expected, the blood pressures of people in the intensive treatment group had a greater reduction in blood pressure than the standard group.
Encouragingly, the results showed that the average cerebral blood flow increased from 38.90 to 40.36 mL per 100g per minute in the intensive treatment group, with no increase in the standard treatment group. This means blood flow improved rather than declined. Similar effects were found when looking at blood flow in gray, white, and periventricular white matter (the periventricular area is deep within the brain and is more susceptible to reduced blood flow).
The effect was similar across different groups defined by age, sex, race, having chronic kidney disease, orthostatic hypotension (low blood pressure when you stand up), and frailty, but there was a larger increase in blood flow in people with a history of cardiovascular disease (diseases of the heart and blood vessels).
The was no real difference between different blood pressure medicines used.
The study has some limitations including a small sample size and only two time points, which can’t give more detail about changes over time.
Meanwhile, more research shows a lower target may prevent strokes
The SPRINT MIND results were published soon after a separate study showed that intensive treatment might prevent or delay strokes in older adults. The analysis looked at nine randomized clinical trials (a high-quality study design), including the SPRINT study, with data for nearly 40 000 people aged over 65. They found that with more intensive treatment it took 1.7 years to prevent one stroke in 200 people.
The ‘time to benefit’ varied with how high blood pressure was. For those with systolic blood pressure under 150mmHg it was longer, and if it was over 190mmHg it was shorter, showing the most impact could be had in people with higher blood pressure.
The authors said: "A treatment's time to benefit is an especially important consideration for patients with a limited life expectancy who may experience immediate burdens or harms from any additional medication."
See the paper in the Journal of the American Geriatrics Society.
Phil Pyatt, CEO of Blood Pressure UK says: “These results from the SPRINT MIND study showed that intensive treatment of high blood pressure was associated with improved blood flow in the brain, rather than reduced, especially in people with a history of cardiovascular disease. This should alleviate some of the worries around reducing blood pressure too much, however, the patient’s general health and other conditions will need to be taken into consideration.”
Read the paper in JAMA Neurology.