Trends in the incidence of smoking-associated cancers in Norway, 1954-93.

A large proportion of cancer cases have been attributed to tobacco smoking. In Norway, the proportion of smokers was 64% in men and 27% in women in 1960. Since then, the difference in the proportion of smokers between the genders has diminished and the proportion at present is 30-40% in both genders. The aim of the present study was to explore trends in the risk of the most common smoking-associated cancers in Norway based on incidence data from the national population-based cancer registry. The nearly complete registration of cancer cases in the entire country has been carried out for more than 40 years. The types of cancer included in this study were cancers of the lung, urinary bladder, kidney and pancreas, and a group of cancers of the upper digestive and respiratory tract. The incidence of all the cancers studied increased in both genders during 1954-93. The largest relative increase was observed in lung and bladder cancer. In female lung cancer, the risk increased dramatically by successive birth cohorts. Interesting differences were revealed between the trends in males and females. It seemed that the lung-cancer incidence increased more rapidly, relative to the other smoking-associated cancers, in females than in males. This is in accordance with other studies suggesting that females are at higher risk of developing lung cancer than males, given similar smoking exposure.