Has the lung cancer risk from smoking increased over the last fifty years?

BACKGROUND: We examine whether the lung cancer risk due to smoking has increased over time. METHODS: Lung cancer risk equations based on prospective mortality data collected from 1960 to 1972 were applied to 5-year birth-cohort-specific estimates of smoking behaviors among white males to estimate lung cancer mortality rates for U.S. white males from 1960 to 2000. These estimated rates were compared to U.S. white male mortality rates for the same birth cohorts. RESULTS: Observed birth-cohort-specific U.S. lung cancer mortality rates are substantially higher than those expected from changes in smoking behaviors, and the proportional difference increases with advancing calendar year. This trend persisted even when the duration term was increased in the risk equation. However, adjusting for changes in cigarette design over time by adding a term for the duration of smoking after 1972 resulted in the predicted rates closely approximating the observed U.S. mortality rates. CONCLUSION: Lung cancer risk estimates observed during the 1960s under predict current lung cancer mortality rates in U.S. white males. Adjustment for the duration of smoking after 1972 results in estimates that reasonably approximate the observed U.S. lung cancer mortality, suggesting that lung cancer risks from smoking are increasing in the United States coincident with changes in cigarette design.