The research, from the National Institutes of Health, suggests that hypertension – blood pressure readings of 140 over 90 or higher – may cause a kind of scarring that interferes with communication between brain cells. That scarring, known as white matter lesions, has been linked to development of Alzheimer’s and other dementias in the elderly. Researchers have found an increase in white matter lesions with each 20-point jump in systolic pressure above the recommended limit. Systolic pressure is the bigger of the two numbers. Those scars can start building up in middle age, although the resulting memory problems may not appear until decades later.

“If you look … for things that we can prevent that lead to cognitive decline in the elderly, hypertension is at the top of the list,” Dr. Walter Koroshetz, deputy director of NIH’s National Institute of Neurological Disorders and Stroke, told The Associated Press. Age is the biggest risk factor for Alzheimer’s disease and other forms of dementia that affect about one in eight people 65 or older.

This evidence of a link is strong enough that the National Institutes of Health will soon begin enrolling thousands of people with high blood pressure into a major study. The aim will be to see if pushing blood pressure lower than currently recommended might better protect not just hearts, but brains.