Risks For Stroke And Heart Disease Reduce Mental Abilities

Editors: A longer version with additional quotes can be seen at http://www.umaine.edu/mainesci/archives/psychology/hypertension.htm.

ORONO, Maine – Analyses of data based on two long-running studies of cardiovascular disease and mental abilities such as learning, thinking and reaction time, are providing powerful evidence that untreated high blood pressure and diabetes result in lowered cognitive ability.

A team of University of Maine psychologists working with physicians and epidemiologists at the State University of New York Health Science Center at Syracuse and the Framingham Heart Study has documented an association between major risk factors for stroke and heart disease and age-related decline in cognitive abilities as measured by neuropsychological tests.

Their results provide strong evidence for several important relationships:

1) hypertension (high blood pressure) and diabetes are independently associated with an accelerated decline in cognitive functioning with advancing age;

2) untreated blood pressure levels in mid-life are associated with decline in cognitive ability many years later;

3) the risk of lowered cognitive functioning doubles in the presence of both hypertension and diabetes and increases even further in the presence of smoking and obesity.

Diabetes and hypertension are the key risk factors that drive these relationships.

UMaine scientists involved in the projects include Merrill F. Elias, professor of psychology at UMaine and adjunct research professor of medicine and public health at Boston University; Michael A. Robbins, senior research associate and cooperating associate professor of psychology; and Penelope K. Elias, adjunct associate professor of psychology at UMaine and senior research associate in mathematics and statistics at Boston University. They work closely with Philip A. Wolf (neurology) and R. B. D’Agostino (epidemiology and biostatistics) at Boston University.

"Our data, and data from other investigators, should provide an additional incentive for people to control hypertension, diabetes, cigarette smoking and obesity through good health practices or medical treatment," says Elias. "It appears that as the number of risk factors goes up, cognitive functioning goes down," he adds. "We must keep in mind, however, that effective treatment or prevention practices can delay or prevent accelerated cognitive decline associated with cardiovascular risk factors."

The Maine-Syracuse Studies of Hypertension and Cognitive Functioning was started in Syracuse in 1975 by Merrill Elias and David H. P. Streeten, professor of medicine. It has been funded every year since 1977, most recently with $311,177 in support from NIA in 1999. With data from 2,000 subjects, this work firmly established that high blood pressure is a risk factor for lowered cognitive ability.

Subjects receive an extensive examination for hypertension and related risk factors (diabetes, obesity, smoking) and a battery of neuropsychological tests when they enroll and again every five years. Participants have been enrolled continuously up to the present. As a result, the Maine-Syracuse project has created one of the longest running and extensive data bases on blood pressure and comprehensive measures of neuropsychological test performance in the world.

In 1991, with supplemental funding from the National Institute on Aging, the Maine research team obtained data from the Framingham Heart Study on a large sample of subjects who had never been treated for hypertension and to obtain more data on diabetes, obesity, and cigarette smoking.

The Framingham study began in 1950 with a group of about 5,000 participants. Extensive medical data on cardiovascular risk factors have been obtained every two years. A battery of neuropsychological tests was first given to 1,799 of the subjects in 1968 and every two years since then.

"Whether we use measures from the Framingham Study or the Maine-Syracuse study we get the same result," says Elias. "Decline in cognition is strongest with high blood pressure and diabetes and less strong with the other two factors. Nevertheless, the relationship still holds."

Results have been published in Hypertension, the American Journal of Epidemiology, Psychosomatic Medicine, Health Psychology, the Journal of Gerontology, the Psychology of Aging and have been reported at professional meetings including those of the American Heart Association.

The researchers controlled statistically for factors such as age, sex and medication to minimize the chances that the analysis could reflect differences in those areas. They also eliminated from the study people who had suffered a heart attack, stroke, brain trauma, psychiatric illness or dementia.

As their sample population grows older, the Eliases, Robbins and their colleagues intend to pursue the relationship between reductions in cognitive functioning and the eventual onset of dementia and Alzheimer’s Disease.

"It has been hypothesized, although it is yet unproven, that uncontrolled or poorly treated diabetes and hypertension may ultimately progress to dementia in some individuals, but not others. This may be the most exciting area of behavioral science research in the future. We hope that our data will encourage this line of investigation and that we can be part of this effort."

The team has already begun to extend collaborative work to include investigators at Oxford University, England, who are working on cardiovascular risk factors and dementia.