But now it seems we have reached a point of diminishing returns. By one calculation, if we found a cure for all cancers tomorrow, it would add just 3.2 years to overall life expectancy. Eliminating every last form of heart disease would add only 5.5 years. That’s because people who die of these things tend to be old already, and if cancer or heart disease doesn’t get them, something else will. Of nothing is that more true than Alzheimer’s disease. Eradicating it altogether, according to the biologist Leonard Hayflick, would add just nineteen days to life expectancy.
