Most people are familiar with the link between high blood pressure to an increased risk of stroke and heart attack, but high blood pressure can also affect your memory. According to the Alzheimer's Society, long-term studies have shown that people with high blood pressure between the ages of 40–64 are more likely to develop dementia later in life, especially vascular dementia. Vascular dementia is the second most common form of dementia after Alzheimer's disease. It is caused by reduced blood flow to the brain, which starves brain cells of the oxygen and nutrients they need to function correctly. Researchers have known about the link between blood pressure and Alzheimer’s for years. In 2013, investigators showed that older people with high blood pressure, or hypertension, were more likely to have biomarkers of Alzheimer’s in their spinal fluid.
High blood pressure can damage small blood vessels in the brain, affecting parts of the brain responsible for thinking and memory. So logically it would make sense that controlling blood pressure through medication could also lower Alzheimer’s risk. A 2013 Johns Hopkins report published in the journal Neurology confirmed earlier work from Johns Hopkins researchers that found the use of potassium-sparing diuretics reduced the risk of Alzheimer’s nearly 75 percent, while people who took any type of antihypertensive medication lowered their risk by about a third.
What they found was if you didn’t have Alzheimer’s and you were taking blood pressure medication, you were somewhat less likely to develop dementia. And if you had dementia from Alzheimer’s disease and you took certain antihypertensives, the disease was less likely to progress. However, it was not clear if the connection comes from managing the blood pressure better or if the particular drugs might have properties that interfere with other processes relating to Alzheimer’s.
Ages Matters in the High Blood Pressure – Dementia Link
Nearly half of U.S. adults have high blood pressure. According to the FDA, high blood pressure is 130/80 or higher. Stage 1 high blood pressure is 130/80, and stage 2 is 140/90 or higher. If your blood pressure is 180/110 or higher more than once, you should seek medical treatment immediately.
Research shows people who develop high blood pressure before middle age have smaller brains and a higher risk for dementia than those whose blood pressure falls within the normal range. The study, published in October 2021 in the American Heart Association journal Hypertension, found people diagnosed with high blood pressure between the ages of 35 and 44 were 61% more likely to develop some type of dementia within the next decade than those whose blood pressure was normal. The results suggest maintaining good blood pressure control early in life can help reduce the risk of dementia later in life.
In this study, researchers analyzed brain health data – including brain volume size and dementia status – using the UK Biobank, a large database of anonymous health information for half a million people living in the United Kingdom. For every age group, they found those diagnosed with high blood pressure had less brain volume overall, as well as in certain regions of the brain. Those diagnosed with high blood pressure before 35 showed the largest reduction in brain volume compared to those with normal blood pressure, even if their blood pressure later returned to normal.
In a separate analysis, the team looked at the relationship between when people were diagnosed with high blood pressure and whether they developed any form of dementia up to 14 years later. They compared data for 124,053 people with high blood pressure to the same number of people without. The earlier a person develops high blood pressure, the higher the risk of developing vascular dementia. The risk was 69% higher for those diagnosed with high blood pressure between ages 35 and 44 and 45% higher for those diagnosed between ages 45 and 54.
The High Blood Pressure – Dementia Link in Older Populations
Specifically about the older adult population, subsequent research published in JAMA Internal Medicine in January 2022, reported high and low blood pressure levels among different older age groups were associated with varying dementia risks. The prospective observational study showed that high systolic blood pressure in people more than 60 years old decreases the risk of dementia. Still, both lower and higher blood pressure are associated with decreased dementia risk in people older than 75.
Although midlife hypertension is associated with an increased risk for dementia, this risk in older people has not been well researched. Previous studies have reported a U-shaped association between blood pressure and dementia risk, where both high and low blood pressure are associated with increased risk; however, the evidence for this association is limited.
Researchers analyzed data on more than 17,000 participants from seven cohort studies and divided the participants into different age groups. In the younger age groups (60 to 70 years old), higher blood pressure was associated with lower dementia risk. The older age groups (75 years and older) showed a U-shaped association where high and low blood pressures were associated with decreased dementia risk. Interestingly, these associations for decreased dementia risk were not attributable to longer survival with lower blood pressure.
This study provides new evidence about how blood pressure affects dementia risk in older people, which previously has not been clearly defined. The researchers note that these observational study results contradict evidence from randomized controlled trials, including the NIA-supported Systolic Blood Pressure Intervention Trial - Memory and Cognition in Decreased Hypertension (SPRINT MIND) study that suggested controlling high blood pressure can reduce dementia risk. They explain that the novel association in this study may be because their cohorts consist of a broader, older population rather than a specific subgroup of older people with high blood pressure and other cardiovascular risk factors.
Since this was an observational study, the study authors suggest further research is needed to understand the cause behind the associations that it found, including randomized controlled trials to find the best strategies for controlling blood pressure in older people.
Mitigating the High Blood Pressure – Dementia Risk in Mid-Age Population
In American Heart Association Scientific Sessions 2023, Abstract in LBS.04 covered a four-year blood pressure intervention program in rural China aimed at significantly reducing systolic blood pressure by an average of 22 mmHg and risk of all-cause dementia by 15% in people with high blood pressure.
The trial was conducted from May 2018 through March 2023. The average age of study participants at enrollment was 63 years old. 61% identified as women, and 39% as men; researchers observed similar reductions in blood pressure and dementia risk in women and men. The study was conducted in 326 villages in rural China and included approximately 34,000 adults, ages 40 and older, with an untreated blood pressure of 140/90 mm Hg or higher, or 130/80 mm Hg or higher for people at high risk for cardiovascular disease or those currently taking blood pressure medication.
Half of the villages were randomly assigned to a village doctor-led intensive blood pressure intervention strategy, and half of the villages were randomly assigned to usual care. The trained interventionists initiated and titrated antihypertensive medications based on a simple treatment protocol in which the medication dose was adjusted with a target blood pressure of less than 130/80 mm Hg. The village doctors also provided discounted and free medications to patients and conducted health coaching on lifestyle modifications, home blood pressure measurement, and medicine adherence.
The analysis found that the people in the intervention group showed significant improvement in blood pressure control and reduced dementia and cognitive impairment, with no dementia compared to those who received usual care. Future studies are needed to examine whether lowering blood pressure will reduce the risk of dementia among adults with a high risk for dementia without high blood pressure.
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