Age-related biology and diseases of muscle and nerve

Age-related biologic changes in neurons and skeletal muscles commonly affect neuromuscular function and strongly influence the expression of neuromuscular disease. Of primary importance is the attrition of entire motor units, with resultant neurogenic atrophy of skeletal muscle. Other age- related processes are sensory neuronal loss, distal axonal degeneration, axonal atrophy, accumulation of multiple mitochondrial DNA mutations in muscle and physical inactivity and deconditioning. The decline for the most of these begins in early life and proceeds steadily; the curious lack of an abrupt fallof with age is not yet accounted for by any theory of pathogenesis. Fortunately, some of the motor loss in the elderly can be overcome in part by exercise training programs.