Washington » If the cardiologist's warnings don't scare you, consider this: Controlling blood pressure just might be the best protection yet known against dementia.

In a flurry of new research, scientists scanned people's brains to show hypertension fuels a kind of scarring linked to later development of Alzheimer's disease and other dementias. Those scars can start building up in middle age, decades before memory problems will appear.

The evidence is strong enough the National Institutes of Health soon will begin enrolling thousands of hypertension sufferers in a major study to see if aggressive treatment -- pushing blood pressure lower than currently recommended -- better protects not just their hearts but their brains. "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," said Walter Koroshetz, deputy director of NIH's National Institute of Neurological Disorders and Stroke. 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.

Scientists have long noticed some of the same triggers for heart disease -- high blood pressure, obesity, diabetes -- seem to increase the risk of dementia, too. But for years, they thought the link was with "vascular dementia," memory problems usually linked to small strokes, and not the scarier classic Alzheimer's disease.

Now those lines are blurring as specialists realize that many if not most patients have a mix of the two dementias. Somehow, factors like hypertension -- blood pressure readings of 140 over 90 or higher -- that weaken arteries also seem to spur Alzheimer's disease-like processes.