Reinforcing Reliability Theory
The Reliability Theory of Aging provides a powerful lense through which to view other research. Take this piece from EurekAlert on chronic illness, inflammation and what is effectively an increased rate of degenerative aging: "Older women with chronic cytomegalovirus (CMV), a lifelong viral infection, were found to have more than triple the risk of being frail than those who did not have the infection ... Further data showed that women who had both the viral infection and high levels of interleukin-6 (IL-6), a marker of inflammatory response, were even more likely to be frail than those who had either alone." Our bodies are complex machines; like any machine, those subject to greater rates of damage will tend to degenerate and fail more rapidly. This is why some historical gains in life span can be attributed to widespread reduction in chronic disease.
Link: http://www.eurekalert.org/pub_releases/2005-06/bpl-cim060805.php