Measurement of brain atrophy of aging using X-ray computed tomography: sex difference in 1045 normal cases

We measured brain volume of 1,045 subjects with no brain damage using x-ray computed tomography and investigated brain atrophy of aging. Severity of brain atrophy was estimated by brain atrophy index (BAI): BAI (%) = 100 (%) X (cerebrospinal fluid space volume/cranial cavity volume). Atrophy of the brain began with statistical significance in the forties in both sexes. In males 40-49 years of age the mean BAI was 1.0% greater (p less than 0.001) and the S.D. of BAI was 1.1% greater (p less than 0.001) than those in their thirties. In females of 40-49 years the mean BAI was 0.5% greater (p less than 0.001) than that in their thirties, but there was no statistical significance between the two S.D.'s of both decades. The BAI increased exponentially with the increasing age from thirties in both sexes. Correlation coefficients were 0.702 (p less than 0.001, n = 471) in males and 0.721 (p less than 0.001, n = 480) in females. From the regression coefficients it was calculated that the BAI was doubled in 19.4 years in males and 17.4 years in females after thirties.