The strengths of our study include its size, prospective design, national scope, and 50-year time span. Our results provide estimates of temporal changes in cause-specific mortality and the contemporary risks from smoking in the United States. Its limitations are that it principally represents whites, 50 years of age or older, who were born between 1870 and 1954. We could not assess risks among younger contemporary smokers. Most current smokers in the contemporary cohorts had smoked for at least 30 years, limiting the range over which we could examine the influence of the duration of smoking.
