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In the first report, researchers found that high blood pressure increased the risk of developing disabilities, such as not being able to lift objects, walk up or down stairs, or bathe oneself.
"High blood pressure affects many aspects of a person's life," said lead researcher Dr. Ihab Hajjar, an instructor in medicine at Harvard Medical School. "Not only does it affect the vascular system and the heart and the brain and kidney, but it also affects well-being -- the ability to be independent, ability to perform daily activities, and be physically active."
Individuals who have lower blood pressure tend to develop less disability later in life and show less decline in their physical abilities compared with people who have higher blood pressure, Hajjar said. "This is a new aspect of the risk of high blood pressure," he noted.
The report was published in the December issue of Hypertension.
Hajjar's team collected data on 999 people who took part in the Charleston Heart Study, which started in 1960. Among these people, 70 percent had high blood pressure, but only 21 percent had their blood pressure controlled to optimal levels.
The researchers found that people with high blood pressure were more likely to have difficulty lifting objects, walking up or down stairs, or bathing themselves compared with people who had normal blood pressure.
In addition, people with high blood pressure who didn't have disability in their 80s did have a 15 percent to 36 percent increased risk of developing one of the three types of disabilities by the time they were checked in their early 90s, compared with those with normal blood pressure.
According to Hajjar, people who had their blood pressure controlled by medications fared as well as those who had normal blood pressure. "Controlling blood pressure may lower the risk of disability," he said.
In the second study, in the same issue of Hypertension, Shari R. Waldstein, a professor of psychology at the University of Maryland, Baltimore County, and her colleagues reported that stiff arteries may be associated with the decline in mental function that often accompanies aging.
"People with stiffening of their arteries show a decline in memory and concentration as they grow older," Waldstein said.
The Maryland researchers collected data on 1,749 people in the Baltimore Longitudinal Study of Aging, which was started by the U.S. National Institute on Aging in 1958.
During the study, participants were screened for increased pulse pressure, which is the difference between the maximum and minimum blood pressures produced during one heartbeat. In addition, their brain function was tested. This was done through tests of verbal and non-verbal memory, working memory, and attention.
In addition, Waldstein's team looked at additional data on 582 people who had their pulse wave velocity measured. Measuring pulse wave velocity is a new method for analyzing pulse pressure. Rising pulse pressure is an indicator of arterial stiffness.
The researchers found that increases in pulse pressure and pulse wave velocity affected memory. However, arterial stiffness wasn't linked to attention, hand-eye coordination, the ability to name objects, and speech fluency.
"Arterial stiffening negatively impacts cognitive performance before people have a stroke or develop dementia," Waldstein noted.
The findings suggest that arterial stiffness may be a potential target for drugs to help preserve mental function, Waldstein said. "Early treatment of cardiovascular risk factors that lead to arterial stiffening may help to preserve brain functioning as people age," she suggested.
One expert isn't sure whether high blood pressure is a cause of disability and dementia, or whether it's a marker associated with these conditions.
"Whether reducing blood pressure reduces disability and dementia isn't really known," said Dr. Harlan M. Krumholz, a professor of medicine at Yale University School of Medicine.
"It's part of a complex syndrome," he said. "Having high blood pressure is associated with having small sub-clinical strokes and heart disease, and there can be other complications from medications that don't interact well with each other."
Krumholz thinks that for any given patient, the reasons for dementia and disability are complex. "But, even as we are trying to sort out what these studies mean, the clear and unequivocal recommendation for people is to get high blood pressure under control," he said.
SOURCES: Ihab Hajjar, M.D., instructor, medicine, Harvard Medical School, Boston; Shari R. Waldstein, Ph.D., professor, psychology, University of Maryland, Baltimore County; Harlan M. Krumholz, M.D., professor, medicine, Yale University School of Medicine, New Haven, Conn.; December 2007, Hypertension
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