Variations in the size of the human brain. Influence of age, sex, body length, body mass index, alcoholism, Alzheimer changes, and cerebral atherosclerosis.

The various factors which determine brain weight and volume of the lateral ventricles were studied in an autopsy material of 467 cases. The material consisted of 64 men and 17 women between 45-54 years and 196 men and 190 women between 70-79 years. The weights of the cerebral hemispheres and of the cerebellum and brainstem were determined separately. The volume of the lateral ventricles was determined by weighing the hemispheres with and without water in the lateral ventricles. The recorded variables were age, sex, body length, body weight, cerebral atherosclerosis, Alzheimer changes and alcoholism. Cerebral atherosclerosis and Alzheimer changes were quantitated by morphometric methods. The results were analysed by conventional and multivariate statistical methods. The following observations were made: In normal brains there was a significant correlation between the weight of the supra- and infratentorial parts. Similarly, there was a significant correlation between the size of the lateral ventricles and the weight of the cerebral hemispheres. Women had smaller brains than men even when the difference in body length was taken into account. The difference was approximately 110-115 g for the whole brain after correction for other variables. Women had also smaller lateral ventricles than men, but this difference was in proportion to the smaller size of their hemispheres. There was a physiologic decline in brain weight and a widening of the lateral ventricles with increasing age. This shrinkage probably started after the age of 55. There was a clear correlation between body length and brain weight. The estimated increase in brain weight was approximately 3 g per cm body length. There was a decreasing brain weight and an increasing ventricular size with a decreasing body mass index. This shows that emaciation leads to a decrease in brain size. Severe Alzheimer changes caused a statistically significant enlargement of the lateral ventricles both in men and women. There was a general trend for brain weight reduction in cases with severe Alzheimer changes but the decrease was statistically significant only in old women, and it could not be entirely excluded that the weight reduction in part was due to a concurrent emaciation rather than to the Alzheimer changes per se. In the majority of the cases, the Alzheimer changes were mild and had probably progressed slowly with age. A few cases had very severe changes.(ABSTRACT TRUNCATED AT 400 WORDS)