It seems evident that much of the gain in healthy life span over the past hundred years is the result of a large reduction in chronic disease - less disease means less acculumated damage to the complex machinery of your body, which leads to a better chance at a longer life, at least according to the Reliability Theory of aging. It is also established that at least a few age-related conditions are caused by or aggravated by forms of chronic infection. The latest article from SAGE Crossroads takes a look at this topic:
Since the discovery of Alzheimer's disease (AD) a century ago, researchers have probed many possible causes for the brain-ravaging illness, from nutrient deficiencies to the aluminum in cooking pans. But if an unorthodox hypothesis proves correct, the cause of AD was right under our noses all the time - or even inside them. According to a growing band of scientists, many of old age's scourges - including atherosclerosis, AD, and some cancers - stem from infections by bacteria and viruses. The evidence so far is inconclusive, but if research confirms the contention, doctors might be able to use the arsenal of antimicrobial weapons to prevent or even treat some of the most dreaded illnesses of old age.
Calls for greater government intervention aside (no surprise considering the source), it's clear that much more work needs to be done to conclusively link common age-related conditions to infectious agents. It is an attractive idea, as identifying a problem species of bacteria or virus would open the door to new and effective prevention strategies. The attraction doesn't mean these theories are necessarily right in the cases we'd like them to be, however. More research would seem to be justified, but bear in mind my earlier comments:
I point this out as a matter of interest - it is of course still that case that far more progress in healthy life extension can and should be made by directed research into extending the healthy human life span. We do need cures for chronic age-related conditions (infectious agents or not), but a great deal of funding is already invested in that research. Not so for the fight to cure aging, alas.