Normal volunteers, aged 30 to 99 years, were studied with MRI. Age was rela
ted to estimated volumes of: gray matter, white matter, and CSF of the cere
brum and cerebellum; gray matter, white matter, white matter abnormality, a
nd CSF within each cerebral lobe: and gray matter of eight subcortical stru
ctures. The results were: 1) Age-related losses in the hippocampus were sig
nificantly accelerated relative to gray matter losses elsewhere in the brai
n. 2) Among the cerebral lobes, the frontal lobes were disproportionately a
ffected by cortical volume loss and increased white matter abnormality. 3)
Loss of cerebral and cerebellar white matter occurred later than, but was u
ltimately greater than, loss of gray matter. It is estimated that between t
he ages of 30 and 90 volume loss averages 14% in the cerebral cortex, 35% i
n the hippocampus, and 26%, in the cerebral white matter. Separate analyses
were conducted in which genetic risk associated with the Apolipoprotein E
is an element of4 allele was either overrepresented or underrepresented amo
ng elderly participants. Accelerated loss of hippocampal volume was observe
d with both analyses and thus does not appear to be due to the presence of
at-risk subjects. MR signal alterations in the tissues of older individuals
pose challenges to the validity of current methods of tissue segmentation.
and should be considered in the interpretation of the results. (C) 2001 El
sevier Science Inc. All rights reserved.