Effects of age on tissues and regions of the cerebrum and cerebellum

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.