The association between smoking quantity and lung cancer in men and women

Background: Studies have shown that for the same quantity of cigarettes smoked, women are more likely to develop heart disease than men, but studies in lung cancer have produced conflicting results. We studied the association between smoking quantity and lung cancer in men and women. Methods: Using data from The Health Improvement Network (a UK medical research database), we generated a data set comprising 12,121 incident cases of lung cancer and 48,216 age-, sex-, and general practice-matched control subjects. We used conditional logistic regression to calculate ORs for lung cancer according to highest-ever-quantity smoked in men and women separately. Results: The odds of lung cancer in women who had ever smoked heavily compared with those who had never smoked were increased 19-fold (OR, 19.10; 95% CI, 16.98-21.49), which was more than for men smoking the same quantity (OR, 12.81; 95% CI, 11.52-14.24). There was strong evidence of a difference in effect of quantity smoked on lung cancer between men and women (interaction P < .0001), which remained after adjusting for height (a proxy marker for lung volume). Conclusions: Moderate and heavy smoking carry a higher risk of lung cancer in women than in men, and this difference does not seem to be explained by lung volume. The findings suggest that extrapolating risk estimates for lung cancer in men to women will underestimate the adverse impact of smoking in women.