Kas Thomas writes: "It may seem paradoxical, but according to CDC data, eliminating the No. 1 and No. 2 causes of death in the U.S. (heart disease and cancer) will add only 6.7 and 3.3 years, respectively, to life expectancy. Why so little? Epidemiologists and public health experts (like Conrad Taeuber) have studied the problem. A key factor is that if you cure a childhood killer disease it contributes much more to overall life expectancy than if you cure a late-in-life disease. But now that all (or almost all) major killer diseases of childhood have been addressed, what are the implications for increasing human life expectancy? Will it really matter if we cure cancer? Will it matter if we cure heart disease? Are significant further gains in human life expectancy out of reach?"