Late-Onset Hypertension May Protect Against Dementia

A new study suggests that high blood pressure may lower the risk of developing dementia in older patients. Previously, hypertension was thought to be a risk factor for dementia.

Millions of individuals around the world have dementia. In the United States alone, 5 million people have been diagnosed with Alzheimer’s disease, which affects 1 in 3 elderly patients.

Findings from numerous studies have pointed to hypertension in midlife as a risk factor for developing dementia, but results from a new study, published by Alzheimer’s and Dementia, indicate that the opposite may be true in patients age 90 and older.

Included in the study were 559 patients, of whom approximately 75% were highly educated, 99% were Caucasian, and 71% were female. At baseline, no patients had dementia. The investigators followed the patients for nearly 3 years, and evaluated their cognitive status every 6 months.

Every 6 months, patients received neurological and neurophysical examinations, and investigators also reviewed their medical records to determine if they were diagnosed with hypertension, according to the study.

The investigators first determined the link between dementia risk and the patients’ self-reported history of hypertension.

Then, they calculated the link between age of hypertension onset and dementia risk by using patients who did not have hypertension as a reference group, the authors wrote. The researchers also calculated the link between hypertension at baseline and dementia risk using blood pressure as the reference.

During follow-up, 40% of patients were diagnosed with dementia, and 61% were diagnosed with hypertension. A majority of patients with hypertension were diagnosed over 70-years-old, although 19% were diagnosed at age 80 or older, according to the study.

The investigators found that patients with hypertension at baseline had a lower risk of developing dementia, but these findings were not said to be statistically significant. However, there was an inverse relationship between dementia risk and the severity of hypertension.

Patients who were diagnosed with hypertension at age 80- to 89-years-old had a significantly reduced risk of developing dementia, compared with patients who had normal blood pressure, according to the study. Patients diagnosed at 90-years-old were observed to have the lowest risk of developing dementia.

This is the first study to assess dementia risk in terms of the age of hypertension diagnosis.

"These new findings suggest some risk factors for dementia may change over the course of our lives," said Maria Carrillo, PhD, Alzheimer's Association chief science officer. "We have seen similar results in past studies comparing body mass in older adults with dementia risk."

The researchers believe that blood flow in older adults may play a role in their findings. Normal cognition requires a certain blood flow that may change with age. Patients that develop hypertension at an older age may have developed a mechanism to keep up with the necessary blood flow, according to the study.

Although unlikely, the researchers indicate that certain antihypertensive drugs may reduce dementia risk. However, if this was true, patients who were taking the drugs for long periods of time would have a decreased risk of developing dementia.

The investigators also hypothesize that certain neurodegenerative processes may cause a decline in blood pressure, instead of the opposite. In theory, individuals who develop dementia would also have high blood pressure.

"Before we can make the leap to suggesting changes to blood pressure recommendations for reducing dementia risk in clinical care, we need more research to confirm and explain our findings,” said Dr Carrillo. “This includes investigations into the underlying biology of hypertension and brain function."

Additional studies are needed to determine the underlying causes of the observed relationship, according to the study.

"We need to understand the bigger picture of what protects brain health throughout our entire lives, including our later years," concluded lead researcher Maria Carrillo, MS, ScD. "Looking at dementia in this group is critical since it is the fastest growing segment of the U.S. population with the highest rate of dementia."