Biological effects of aging on bone and the central nervous system.

The skeletal and nervous systems express conspicuous signs of aging in humans in the form of osteoporosis and senile dementia, the most common diseases affecting the elderly population. Although the prevalence of these diseases progressively rises with advancing age, especially in females, the interrelationship between the degenerative changes of the skeletal and nervous systems has not been studied in detail. Defective 1,25(OH)2D synthesis in chronic renal failure is known to cause renal osteodystrophy and is also associated with the appearance of dialysis encephalopathy and a decrease of the conduction velocity of peripheral nerves. Calcium content of the nervous system is increased in this condition, suggesting the existence of generalized abnormalities of calcium metabolism, which affect both the skeletal and nervous system. The mild, chronic renal failure of aging, and the consequent secondary hyperparathyroidism, might therefore contribute to the development of nervous degenerative diseases.