Age-related changes in the morphology of cerebral capillaries do not correlate with cognitive decline

The effects of age on cerebral capillaries have been examined in area 46 of the prefrontal cortices of sixteen rhesus monkeys, ranging in age from 5 to 35 years. Fourteen of the monkeys had been behaviorally tested prior to their brains being prepared for electron microscopic examination. It was found that whereas the thickness of the outer basal lamina adjacent to the glial limiting membrane increased with age and showed increasing numbers of splits, the inner basal lamina between endothelial cells and pericytes did not become thicker with age, and did not show splitting. There were also no age-related changes in the extent of the coverage of endothelial cells by pericytes and no change in the frequency of mitochondria in endothelial cells. The factors that did change with age, namely, the thickness of the outer basal lamina and the increased numbers of splits in this lamina showed no correlations with the cognitive status of the monkeys, suggesting that thickening of the outer basal lamina does not contribute to cognitive decline.