The evidence that high blood pressure is worrisome for the brain as well as for the heart continues to mount: A study published today in the St. Paul-based journal Neurology reports a link between high blood pressure and cognitive problems (difficulty with memory and other kinds of thinking) in people aged 45 and older.

(Younger readers: Before you smugly click away from this article, be aware that a study a few years back found that people aged 18 to 46 were just as susceptible to blood pressure-related declines in cognitive performance as older people.)

Diastolic blood pressure — the second number in a blood pressure reading — appears to be the culprit in the current study. With each 10-point increase in diastolic pressure, the odds of developing cognitive problems increased by 7 percent.

Diastolic blood pressure measures the pressure on your arteries when your heart is resting, or between heartbeats.

The study found no link between cognitive problems and systolic pressure — the first number of a blood pressure reading, which measures pressure on your arteries when your heart is beating and pumping blood.

High blood pressure is defined as a reading of 140/90 mm Hg (millimeters of mercury) or higher, according to the American Heart Association (AMA). But the AMA recommends that everybody should aim for a blood pressure no higher than 120/80 mm Hg.

Cause unclear
Why would high diastolic pressure have such a negative impact on brain function? Scientists aren’t sure, but other research has suggested that high diastolic blood pressure weakens small blood vessels in the brain, causing blood to leak out and damage brain cells, including the connections (synapses) that enable those cells to communicate with each other.

As the authors of this study point out, other research on high blood pressure and cognition has produced conflicting results, with some studies, but not all, finding a relationship between high BP and a downward trajectory of thinking skills. Nor do the authors believe this study is definitive. Much more research is needed.

The study was funded by the National Institute of Neurological Disorders and Stroke (NINDS). It used data collected from almost 20,000 people who participated in the large Reasons for Geographic And Racial Differences in Stroke (REGARDS) Study.

NB: You can have high blood pressure and not know it (it’s not called “the silent killer” for nothing). So if you haven’t had your blood pressure checked recently, be sure to do so. To get a true diagnosis, you’ll need to be tested more than once, for many factors can skew a single blood pressure reading — even the weather.

High blood pressure is treated with medications and lifestyle changes (those all-important actions like exercising regularly, eating more healthful foods, taking steps to reduce stress, and not smoking). Many people are successful with lifestyle changes alone. The National Heart Lung and Blood Institute has a guide you can download to get started.

And do get started. Your brain as well as your heart will thank you.