Outside of your genetic makeup, few things are definitively linked to Alzheimer’s disease and other degenerative brain conditions. Unlike heart disease, which is affected by behaviors like diet, exercise and smoking, science hasn’t documented many risk factors that make the brain more vulnerable to dementia—although there are hints that things like physical activity and brain games might help to protect against cognitive decline.
But in a study published in the journal Neurology, researchers led by Dr. Zoe Arvanitakis, medical director of the Rush Memory Clinic at Rush Alzheimer’s Disease Center, find more evidence that blood pressure may be one of those risk factors.
Previous studies have implicated high blood pressure as a possible risk factor for dementia, including Alzheimer’s dementia, but there are few studies exploring how blood pressure, particularly among older people, affects tissues in the brain. In the study, Arvanitakis and her colleagues measured the blood pressure of nearly 1,300 elderly people, aged 59 to 102 years, and followed them until they died, on average eight years after enrolling in the study. The scientists performed autopsies on the brains to document the presence of brain lesions, including signs of Alzheimer’s disease, which is characterized by the presence of protein plaques known as amyloid, and tangles of dying and dead nerve fibrils known as tau.
The American Heart Association says that blood pressure should ideally be 120/80 mmHg or below. During the study, the average blood pressure was about 134/71 mmHg, which is considered pre-hypertensive. People with higher blood pressure across the study period tended to have more brain lesions, known as infarcts, which are areas of dead brain tissue that have lost their blood supply. Infarcts can lead to strokes, but many go undetected. People with higher blood pressure also showed more tau tangles, although they did not show significant differences in the other Alzheimer’s feature, amyloid plaques. In fact, an increase in systolic pressure (the top blood pressure number) from 134 mmHg to 147 mmHg was linked to a 46% higher chance of having one or more brain infarcts.
“We think that it’s potentially biologically plausible that altered blood pressure later in life can cause infarcts [in the brain], given the body of literature in which we know that blood pressure is associated with stroke,” says Arvanitakis. She says the study does not show that high blood pressure actually causes brain lesions, and further research is needed to explore that connection.