Big Blood Pressure Drop May Lead to Alzheimer's

THURSDAY, July 1, 2004 (HealthDayNews) -- A drastic drop in blood pressure may be a harbinger of Alzheimer's disease and other forms of dementia in older people, new Swedish research finds.

The study, which followed nearly 1,000 Stockholm residents aged 75 or older, found that a 15-point drop in systolic blood pressure (the higher number in a blood pressure reading) was linked to a threefold increase in the risk of dementia. The report appears in the July 2 issue of Stroke.

Doctors consider a blood pressure reading of 120/80 as healthy.

This latest discovery adds complexity to the relationship between blood pressure and dementia. Several previous studies have shown high blood pressure in the midlife years is associated with an increased risk of dementia later in life.

The new finding is open to several explanations, said Dr. Laura Fratiglioni, a professor of geriatric epidemiology and leader of the group at the Karolinska Institute that did the study. One possibility is the same process that results in the brain damage of dementia also causes a drop in blood pressure.

"My personal hypothesis is that a decrease in blood pressure may facilitate a process that has already begun," Fratiglioni said, with lessened blood flow to the brain increasing the damage to brain cells that results in dementia.

There's also an outside chance that overzealous efforts by patients and their physicians to lower blood pressure might lead to brain damage, Fratiglioni said. "The message is not to treat high blood pressure but to treat it in a good way," she added, with careful monitoring of blood pressure levels through the years.

Each participant in the study had a blood pressure measurement and physical examination at the start, and again three and six years later. Blood pressure did drop slightly in participants who didn't develop dementia, but the drop was much sharper in those who developed the condition. And as blood pressure dropped, the severity of dementia increased.

Bill Thies, vice president for medical and scientific affairs at the Alzheimer's Association, said the only thing certain about the relationship between blood pressure and the loss of mental function seen in dementia is that "it is complex."

"It is possible that dementia causes a decrease in blood pressure," Thies said. "The same thing that causes damage to the brain may cause a decrease in blood pressure."

The relationship between high blood pressure earlier in life and the later development of dementia has been observed in several studies, he said. "The ultimate study would be to actually take a group of people and lower their systolic blood pressure in later life to see if it is beneficial or not," Thies said. "But that would be a difficult area to investigate."

Any link between high blood pressure and dementia later in life "is still obscure, and may be multifactorial," he said, but "there are increasing reasons to think that Alzheimer's disease and blood vessels and blood flow are related."

However, the fact that high blood pressure increases the risk of heart disease and stroke is unchallenged, Thies added, and doctors treating patients with Alzheimer's disease should take that into account.

"Because people have Alzheimer's disease doesn't mean you stop worrying about other medical problems," he said.

More information

The Alzheimer's Association has more on dementia research.