Case-control study of lung cancer during 1994-1997 in the birth cohort in Tasmania, Australia, with an excess of female cases during 1983-1992

Objective: In Tasmania, Australia, lung cancer incidence for 25-44-year-old women has reached that of 25-44-year-old men despite less smoking by the women. We investigated whether this could be due to greater female-than-male relative risk for smoking. Methods: This was a case-control study of lung cancer in the 1939-1964 birth cohort. In person (n = 100) or by proxy, 158 of the 160 cases arising during 1994-1997 were interviewed. Controls were a representative sample of the cohort (response 82.8%). Detailed measurements of tobacco smoking were made by questionnaire, and using the results of 17 machine tests of cigarette "tar" yields. Results: The male smokers had greater accumulated exposure to smoking and, in reversal of the previously reported excess of female cases in this cohort, most (99/160) of the 1994-1997 cases were men. Nevertheless, the proportions attributable to smoking were similar: 0.86 (0.76-0.97) of male cases, and 0.87 (0.74-0.99) of female cases. Calculated relative to male never-smokers, the estimated relative risks were similar for male and female smokers, particularly with exposure measured by cumulative tar yield of all cigarettes smoked. Conclusions: We found no compelling evidence of greater susceptibility to lung cancer for female smokers.