- Researchers analyzed data from five randomized controlled trials assessing the effects of antihypertensive medications on dementia risk.
- They found that taking antihypertensive medications in mid-to-late life lowers dementia risk.
- They noted that future studies should investigate the cognitive effects of lowering blood pressure earlier in life.
Observational studies have demonstrated a strong link between high blood pressure in midlife and an increased risk of dementia and cognitive decline.
However, a recent meta-analysis involving over 17,000 older adults found that those with the lowest dementia risk had high blood pressure.
Randomized controlled trials have meanwhile produced mixed results on the effects of lowering blood pressure on dementia risk.
Further investigation of the link between blood pressure and dementia risk is necessary to develop effective prevention strategies for the condition.
Recently, researchers analyzed five trials that tracked how different blood pressure-lowering treatments influence dementia incidence.
They found that blood pressure-lowering treatments significantly reduced dementia risk.
“The study puts forward an individual participant data analysis of double-blind placebo-controlled trials that all used blinded expert adjudication of dementia according to standardized criteria,” said Dr. Phillip Tully, PhD., registered psychologist and researcher at the University of Adelaide, not involved in the study.
“Consequently, this study constitutes the strongest evidence to date on antihypertensive drugs and dementia risk,” Dr. Tully told Medical News Today.
“The data obtained across multiple countries utilizing various antihypertensive drugs versus placebo suggests that irrespective of the type of antihypertensive drug, blood pressure lowering among individuals with hypertension is associated with lower dementia risk.”
– Dr. Tully
The study appears in the European Heart Journal.
Blood pressure medications and dementia
For the study, the researchers included five randomized, double-blind, placebo-controlled trials with 28,008 individuals at an average age of 69.1 years from 20 countries. All trials measured blood pressure at baseline, annual intervals, and follow-up.
Data also included incident dementia, death, and stroke alongside baseline characteristics such as body mass index (BMI), smoking status, and education history.
The study followed the participants for an average of 4.3 years and recorded 861 cases of dementia.
In the end, the researchers found that those who took blood pressure medications had a 13% lower risk of dementia.
The researchers noted that these results remained after accounting for factors including age, baseline blood pressure, and stroke history.
The researchers noted that antihypertensive treatments did not affect cognitive decline.
The researchers concluded that blood pressure-lowering treatments in late-mid and later life lower dementia risk.
Treating hypertension to prevent dementia
When asked how lowering blood pressure may prevent dementia, Dr. Emil Tsai, Ph.D., M.A.S., chief scientist and C.E.O. of SyneuRx, and Professor at the Department of Psychiatry and Behavioral Sciences at the University of California, Los Angeles (UCLA), told MNT:
“Blood pressure measures the force that is applied to arteries as blood is circulated through the body. High blood pressure or hypertension is a result of our blood vessels getting older and losing elasticity, causing the force of blood pushing against the walls of blood vessels to be consistently too high.”
“High blood pressure causes strain on the blood vessels over time, this can cause the walls of arteries to become thicker and stiffer as well as narrower, this is called arteriosclerosis. This narrowing of the arteries can happen in the brain, causing a lack of nutrients and oxygen, which causes damage that prevents the brain from functioning properly,” Dr. Tsai added.
“High blood pressure can also cause a patient to suffer a stroke. A stroke can cause brain cell death that may lead to the development of vascular dementia, the second most common form of dementia after Alzheimer’s.”
– Dr. Tsai
MNT spoke with Dr. Philip Blum, a neurologist at Memorial Hermann Mischer Neuroscience Associates, not involved in the study, about the research limitations.
“The obvious presumption is that by reducing vascular disease in the brain, there are more uninjured neurons available to fight the effects of neurodegenerative disease,” said Dr. Blum.
“That presumption is unproven, and considering the nature of these types of studies, it likely will be difficult to test. This leads to the limitations of such studies. They are observational in nature. Imagine doing a study in which the researchers don’t treat hypertension in half of the patients. It would be unethical and will never be done,” he added.
Dr. Tsai added that although the study included 20 countries, it may not be universally applicable as blood pressure is heavily influenced by diet, exercise, and climate.
“Stress on the body experienced in India is very different from the stress experienced in Boston,” he said.
He further noted that the study did not investigate nonpharmacological approaches to lowering blood pressure, which may also affect dementia risk.
Dr. Sandra Narayanan, board certified vascular neurologist and neuro-interventional surgeon at Pacific Stroke & Neurovascular Center at Pacific Neuroscience Institute in Santa Monica, CA, not involved in the study, noted that cognitive impairment may not have been adequately investigated.
“Uniform cognitive screening tools were not used in all trials, so the extent and forms of cognitive impairment may not have been fully characterized,” Dr. Narayanan said. “Certain scales such as the Mini-Mental Status Examination (MMSE) are less sensitive for detecting mild cognitive impairment, and results are influenced by participant engagement and health at the time of administration.”
Implications to improving brain health
Dr. Narayanan noted that these findings add to a substantial body of evidence demonstrating the benefits of lowering blood pressure for brain health.
“Benefits were noted with lowering of as little as a mean blood pressure reduction of 9.6/3.7 mm Hg at 12 months. Since life expectancy in both women and men is projected to increase across racial and ethnic groups over the next four decades, identifying effective dementia prevention strategies is of utmost importance to providers and patients alike,” she said.
“We have looked at older adults in our work [as] this is the age group who are most at risk of developing dementia,” Prof. Ruth Peters, Ph.D., Senior Research Scientist at Neuroscience Research Australia (NeuRA) and Conjoint Associate Professor at the University of New South Wales, Australia, lead author of the study, told MNT.
“But going forwards, it will be important to understand more about blood pressure lowering at earlier ages and its potential impact on later life cognitive function or thinking skills and dementia,” Prof. Peters concluded.
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