Life extension researcher Aubrey de Grey has an interesting article on a concept he calls "life extension escape velocity." He starts by asserting that it's easier to understand the effects of aging--the chemical changes in the body--than the causes, and that it may be possible to fix many of the biochemical effects even without a complete grasp of the causes.
According to de Grey, there are seven different categories of types of aging damage. Each one, if it develops enough, could be lethal on its own. But within each category are multiple causes, and they don't all have to be fixed at once in order to extend life. Some kill you slower than others, and if you fix them as they arise, then you have more time to fix the remaining ones.
So, his hope is that researching the "low-hanging fruit" will keep us alive long enough to figure out some of the harder problems, and that will give us more time to figure out the rest. Here's the good news: "The bottom line, therefore, is that if you're still reasonably healthy when those 30-year-conferring therapies arrive, you probably won't need to die of old age at any age—you'll be able to remain both physically and mentally youthful indefinitely, dying only from accidents and such like, even though the therapies that will make that happen will only be arriving gradually, over many decades or even centuries."
But he cautions that the problems will get more and more difficult to solve, requiring more advanced technologies. De Grey warns, "I think it's quite likely that pure biotechnology will come up against some brick walls by the time we get out to ages like 200 or 250." In the last few paragraphs of his article, he invokes molecular manufacturing: he expects we will need general-purpose nanotechnology--"machinery that we can control as precisely as we control computers."
Of course, if CRN is right about how quickly molecular manufacturing can be developed (and probably will, once militaries and corporations start racing for it), then it will arrive long before anyone has a chance to become 200 or even 150 years old. That's the good news.
The bad news is that in different people, each aging process happens at different rates. If a thirty-year research cycle is enough to keep the average person alive, a fraction will die for lack of the breakthrough in less than 20 years. After several such cycles, the fractions add up, and by this model, most of the population would still have to expect to die of old age sooner or later. (This isn't covered in the article, but I emailed my analysis to de Grey, and he confirmed it as a concern.)
On the third hand, I expect that--if regulation allows--molecular manufacturing should allow a far shorter research cycle than 30 years. With the ability to build custom-designed diagnostic and treatment hardware on the fly for pennies per device, it should be possible for a research group to test and evaluate hundreds of treatments per year, benefiting almost instant feedback--which should make such a rapid testing cycle safer than today's medicine, if it's done responsibly.
A few days ago, I posted a survey that said the public looks forward to medical benefits from nanotechnology. If de Grey is right about the feasibility of fixing the effects of aging a bit at a time, and if I am right about how quickly medical research could be done with high-quality feedback and personalized research tools, then we may see a whole lot more lives saved--at least for a while--than you might expect.
Ps. The implications of extended healthspan are not as scary as most people assume. Birth rate has a much higher potential effect on the population than death rate. End-stage medical care takes more resources than simply staying alive and healthy. That's not to say there are no reasons for concern, but I don't think it should be assumed that trying to slow aging is irresponsible or destructive, as some have claimed. In any case, molecular manufacturing will pose far larger and more urgent problems than a population of healthy hundred-year-olds.