Reduction in regional cerebral blood flow during normal aging in man.

Regional cerebral blood flow (rCBF) was measured by the 133Xenon inhalation method in a selected group of 44 normal non-hospitalized, normotensive subjects aged 19 to 79 years. rCBF was computed as the initial slope index value (ISI). Advancing age was associated with significant reductions in the mean brain and mean hemispheric ISI as well as in individual ISI levels measured from all areas in both hemispheres. Our findings suggest that decline of rCBF is not limited to normal elderly subjects but that it is a progressive phenomenon which begins at an earlier age.