I have a question about the relationship between a graph of mortality rate and years of life. Something like the MRFIT study has graphs that show total cholesterol on the horizontal axis, and deaths per year on the vertical axis. Low cholesterol has more deaths, and high cholesterol has more deaths, but 180-260 mg/dL total cholesterol has minimum death.

Assume that there is a direct relationship between total cholesterol level and mortality rate i.e. if I change my cholesterol level, then I also move to the corresponding death rate. In that case, how does one work out the benefit of changing cholesterol? i.e. can a certain cholesterol change, from total cholsterol y that is outside the area of minimum death, to x which is in the range 180-260 for minimum death, be converted into a number of extra years per life by using the mortality graph?