MONDAY, Dec. 15, 2008 (HealthDay News) -- Sudden surges in blood pressure could make seniors with chronic hypertension a little less smart, new research suggests.
"If you have high blood pressure, on days when your blood pressure spikes higher than normal, cognitive ability is worse than normal," concluded lead researcher Jason Allaire, an assistant professor of psychology at North Carolina State University, in Raleigh.
Whether high blood pressure itself is responsible for the decline in reasoning or whether it's a marker for other factors, such as stress, that result in impaired thinking isn't known. But it's another reason to keep your blood pressure down, experts said.
"This finding suggests that if you have high blood pressure that is not controlled, your cognitive abilities are going to decline faster as you get older," Allaire said.
The report is published in the Dec. 15 issue of the Journal of Gerontology: Psychological Sciences.
For the study, the researchers had 36 people between 60 and 87 years of age take verbal learning tests, letter and number comparison tests, and other cognitive exams. The tests were given twice a day over 60 days. The researchers also measured the participants' ongoing blood pressures.
They found that people with chronic high blood pressure tended to do poorly in cognitive tests when their blood pressure spiked above normal.
However, there was no change in cognitive functioning among people whose average blood pressure was in the low or normal range, even when their blood pressure did rise above normal, Allaire's group noted.
It is possible that chronic high blood pressure could cause problems with cognition, Allaire said, or that spikes in blood pressure could cause changes in the brain that affect thinking.
The findings could also indicate that the stress behind the spike in pressure might cause changes in cognitive function. "So, blood pressure spiking is a marker, and it is actually the stress that's causing worse cognitive ability," Allaire explained.
Dr. Byron Lee, an assistant clinical professor of cardiology at the University of California San Francisco, remained skeptical of a hypertension-thinking link.
"This paper does not convince me that lowering blood pressure would improve cognition," Lee said. "My interpretation of the data is that lowering stress, which will also lower blood pressure, leads to better mental performance. Nevertheless, we already have plenty of health reasons to keep blood pressure low."
Dr. Sarwat Chaudhry, an assistant professor of medicine at Yale University School of Medicine, said more study is warranted.
"Whether daily variations in blood pressure within individuals are associated with reasoning abilities will need to be confirmed in larger studies that also examine the role of emotional stress in causing elevations in blood pressure, and perhaps affecting intellectual performance," Chaudhry said.
In related research, another study finds that popular no-carb or low-carb diets are linked to memory problems.
The results of the study, which are published in the February issue of Appetite, showed that people who eliminated carbohydrates from their diet performed worse on memory tasks.
This decline in cognitive ability didn't happen when calories were reduced generally -- only when carbohydrates were dropped. When individuals started eating carbohydrates again, memory function returned to normal, the researchers found.
"This study demonstrates that the food you eat can have an immediate impact on cognitive behavior," lead author Holly A. Taylor, a professor of psychology at Tufts University in Boston, said in a university news release. "The popular low-carb, no-carb diets have the strongest potential for negative impact on thinking and cognition."
For more information on high blood pressure, visit the American Heart Association.