“These results indicate that it’s very important to know your blood pressure level, even in young adults,” says Donna K. Arnett, PhD, MSPH, professor in the department of epidemiology at the University of Kentucky College of Public Health in Lexington, and a past president of the American Heart Association (AHA) and a volunteer expert for the organization. Dr. Arnett was not involved in this research. “If you are found to be hypertensive, you should seek treatment early,” she adds.
Nearly Half of U.S. Adults Have High Blood Pressure
Blood pressure is simply a measurement of the pressure of blood pushing against the walls of the arteries. If blood pressure stays high for a long time, it can cause damage to organs, including your heart, brain, kidneys, and eyes. According to the Centers for Disease Control and Prevention (CDC), nearly half of adults in the United States — 47 percent or 116 million people — have hypertension, which is defined as a systolic blood pressure greater than 130 milimeters of mercury (mmHg) or a diastolic blood pressure greater than 80 mmHg or are taking medication for hypertension. RELATED: What Is High Blood Pressure? Symptoms, Causes, Diagnosis, Treatment, and Prevention
Hypertension Is Linked With Dementia Risk
Existing research on hypertension and dementia, summarized in a review published in January 2020 in Frontiers in Cardiovascular Medicine, has confirmed that elevation of blood pressure in middle age is linked to cognitive decline, though further research is needed to clarify the relationship. To evaluate how the age of onset of high blood pressure might affect brain changes and dementia risk, researchers analyzed data from participants in the UK Biobank, a large database containing detailed anonymous health information of approximately 500,000 people from the United Kingdom. Participants in the UK Biobank are between the ages 40 and 69 years old who agreed to provide blood, urine, and saliva samples, as well as a detailed history for the purposes of research. RELATED: Dementia: Causes, Symptoms, Treatment, and More In the study, published on October 4, 2021 in Hypertension, an AHA journal, authors compared magnetic resonance imaging (MRI) measurements of brain volume between two groups in the database: a high blood pressure group which contained 11,399 people who had been diagnosed with the condition at different ages: younger than age 35; 35 to 44 years; and 45 to 54 years, and a normal blood pressure group, with 11,399 participants. All the subjects were matched for age and multiple health-related variables in an effort to isolate the potential impact of high blood pressure on the brain as much as possible. In all age categories, the total brain volume was smaller in people diagnosed with high blood pressure, and the brain volume of several regions were also smaller compared to the participants who did not have high blood pressure. A high blood pressure diagnosis before age 35 was associated with the largest reductions in brain volume compared with people with normal blood pressure. Why does brain size matter? Although brain size naturally grows smaller as we age, this study found that people with longstanding hypertension had smaller brains that those who didn’t, says Arnett. “Smaller brain size means there are fewer neurons and fewer connections between neurons, which means the capacity of the brain to process and store information is reduced,” she says. These results were based on a one-time measurement. To prove that hypertension diagnosed at a younger age is associated with a decrease in brain volume over time, future research would need to be conducted in which brain volumes were measured at multiple time points, said Xianwen Shang, PhD, MPH, lead author of the study and a research fellow at the Guangdong Provincial People’s Hospital in Guangzhou, China, in a statement.
Vascular Dementia Risk and Hypertension
To evaluate dementia risk, researchers tracked 124,053 people with high blood pressure to 124,053 participants with normal blood pressure for a median follow-up of 11.9 years to see who developed dementia from any cause. In that time, a total of 4,626 people developed some form of dementia. In comparing the people with high blood pressure to those without it, investigators found the following:
The risk of dementia from any cause was significantly higher — 61 percent — in people who had been diagnosed with high blood pressure between the ages of 35 and 44 years old compared to participants who did not have high blood pressure.The risk of vascular dementia, a type of dementia resulting from impaired blood flow to parts of the brain, was 45 percent higher in the adults diagnosed with hypertension between ages 45 and 54 and 69 percent higher in those diagnosed between ages 35 and 44, compared with participants of the same age without high blood pressure.
Although vascular dementia risk was 80 percent higher in people diagnosed with high blood pressure before age 35, there weren’t many cases of dementia among those younger participants, and the association wasn’t statistically significant. There was no relationship found between age at hypertension diagnosis and the risk of Alzheimer’s disease, a type of dementia linked to proteins that disrupt brain function. The authors acknowledge a limitation of the research is a lack of diversity in the UK Biobank, which is 94.6 percent white. This study provides further evidence that adults of all ages should take steps to prevent hypertension from developing in the first place, says Arnett. “Three attainable ways to reduce your risk of high blood pressure are regular physical activity, maintaining a healthy body weight, and watching your sodium intake,” she says.
