Theories of Biological Aging

It is clear that humans die for a variety of reasons. Usually one or more organ or system is more compromised than the others, so failure of that system is identified as the cause of death. Two examples are heart failure and stroke. Whereas the immediate cause of death in both cases is a blood clot that obstructs blood supply to critical cells (heart muscle cells or neurons, respectively), the aging-related cause is the gradual obstruction of arteries by protein and lipid deposits. Both genetic and environmental factors may contribute to this deposition, but it can hardly be considered programmed. A continuing controversy is whether there is such a thing as aging without such disease, or whether aging is simply the accumulated effects of wear and tear from disease and the various other life stresses.