As many people age, their sugar levels in the blood crawl. In extreme cases, this can lead to diabetes. But a new study suggests that sugar levels in the blood, even moderately high can cause memory impairment and reduce the hippocampus -. Part of the brain critical to store new information
Many elderly people develop a condition called impaired glucose reduced Tolerance- -an of the body's ability to move glucose from the blood into the cells using as energy source. This increases the level of sugar in the blood, which can impair memory. Diabetics tend to score poorly on tests of memory, for example, as individuals with glucose levels in the blood that are not yet diabetic. However, it is unclear whether this loss of memory resulted in brain damage.
Antonio Convit, a psychiatrist at New York University, and colleagues examined 30 healthy older subjects between 53 and 86 years. The team took images of magnetic resonance brain subjects, gave them a battery of cognitive tests, and performed a standard test that measures their ability to remove glucose from the blood. As expected, subjects with sugar levels in the blood less well in memory tests. In addition, the hippocampus was smaller. No other brain structures differ between groups, Convit and colleagues report online this week in the Proceedings of the National Academy of Sciences .
Although the cause of withdrawal does not know, Convit emphasizes that the hippocampus has long been known to be particularly vulnerable to physiological stress. reduced glucose tolerance could provide such stress by starving the hippocampus when it is most needed fuel. "In the long term, that may be causing the damage," says Convit.
This scenario makes sense for Carol Greenwood, a nutritionist at the University of Toronto, who thinks that the hippocampus may be in trouble even before diabetes sets in. It is a "slippery slide down the slope," she said. Neuroendocrinologist Bruce McEwen of Rockefeller University in New York agrees, but expects more evidence to nail him. "At this stage we do not know yet what are the causal factors. "
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Department of psychiatry University of New York
laboratory Bruce McEwens at the Rockefeller University
laboratory Carol Greenwood, University of Toronto
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