In the Know links readers with University of Maine faculty, students and staff with particular expertise. On page 1, Professor of Psychology Merrill Elias answers reader questions on cardiovascular risks related to cognitive function. On page 2, UMaine Professor of Psychology and University of Maine Cooperative Extension Educator Jane Haskell answers reader questions on effective group facilitation skills.
You have been conducting research based on data from the ongoing Maine-Syracuse Longitudinal Study (MSLS) for several years. What did your latest study find?
The study has been conducted for a period of 35 years and involves 2464 persons (age range: 18 to 98 years). Participants live in various areas all across the United States, including Maine, but many still reside in the Syracuse locale in central New York. Unique aspects of the MSLS involve a very large battery of cognitive tests and the long period of longitudinal follow-up of our subjects with respect to health and cognitive performance. In one of our latest studies published in Hypertension, we found that stiffening of the heart arteries resulting from sustained high blood pressure and aging is related to lower cognitive performance for a wide range of clinical measures of cognitive ability (attention, working memory, visual-spatial ability).
What are the most prevalent cardiovascular diseases related to cognitive performance?
We and other investigators find that risk factors for cardiovascular disease, such as high blood pressure, diabetes mellitus, central adiposity, high plasma homocysteine and presence of an ApoE e4 genotype relate modestly to poorer performance on a wide range of cognitive tests. We find evidence indicating that presence of the ApoE e4 alelle (involved in retarded neuron repair after damage) results in an exacerbation of relations between diabetes and lowered cognition, and between high homocysteine (a brain-toxic product of impaired metabolism) and lowered cognition.
How is it that the health of the heart and the brain are related in this way?
The heart pumps blood to the brain. The heart, kidneys and brain are connected via blood circulation. Adequate blood circulation and hence oxygenation of the brain is essential for cognitive performance and chronic fluctuations of oxygen (high and low levels) or sustained oxygen starvation result in destruction of the brain tissue and vessels supplying blood. Over a range of values, the brain is protected against extremes of blood pressure by a mechanism called auto-regulation, but above and below critical high and low levels of peripheral blood pressure (what you doctor measures with the blood pressure cuff), the brain is not protected. Thus, both low and high blood pressure can result in cognitive performance deficits over time and are risk factors for dementia.
Chronic untreated high blood pressure not only affects brain metabolism (including oxygenation), but causes wear and tear on the vessel walls and contributes to the formation of plaque. What is seen in heart arteries is very often seen in the brain and in the kidneys. A clot sent to the brain from the heart (often the result of heart arrhythmia) can result in acute stroke or mini-strokes. The infarctions (dead brain tissue) from mini-strokes accumulate and have a negative effect on cognitive performance. Many individuals experience undetected strokes (silent stroke).
If cardiovascular functioning improves, does cognitive functioning improve?
We have not examined this issue in our longitudinal studies, but we know from controlled clinical trials in the literature that treatment of hypertension in mid-and late life with drugs often produces no change in cognitive performance or only trivial improvement. Exercise combined with heart healthy diet has been effective in lowering blood pressure in individuals designated as pre-hypertensive and is effective in improving cognition regardless of the individuals risk profile. In observational studies, we found that vitamin B12 and foliate improves performance and lowers homocystine levels, a finding that has been replicated in clinical trials. Some of the most dramatic improvements in cognition result from control of diabetes, because the effects of uncontrolled diabetes on cognition are often immediate, larger and more apparent than those of other risk factors, such as high blood pressure.
What are you and your research team investigating next in this area?
We are increasingly focusing on diabetes and cognition. Here we are interested in the effect of genetic factors that exacerbate deficits in cognition in relation to diabetes (e.g., the ApoE e4 alleles) and the role of stiffening of the arteries as measured by pulse wave velocity, a new noninvasive ultrasound electronic measure of how fast pressure waves return from the peripheral vessels to the heart after blood is pumped out of the heart during contraction (systole).
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