Age changes in human vocal muscle.

Micromeasuring studies have been made on the senile changes of the vocal muscle in 109 Japanese males of various ages (18--97 years). For the microscopic differentiation between red and white fibers, paraffin section were stained with phosphotungstic-hematoxylin. The decrease in number after 50 years of age was similar in both red and white fibers, while the volume of both types of fiber somewhat increased with age. However, a slight difference was recognized in the changes between the red and white fibers. The white fibers significantly decreased in number first in the earlier stage of life, and noticeably decreased in number after 80 years of age, with no appreciable increase in volume. In the red fibers, on the other hand, the decrease in number after 80 years was highly significant, and was accompanied by a significant increase in their volume.