HAS RISK ASSOCIATED WITH SMOKING INCREASED - RESULTS FROM THE COPENHAGEN CENTER FOR PROSPECTIVE POPULATION STUDIES

Background. Two recent much cited publications have raised the concern that risk associated with cigarette smoking has so far been underesti mated. In this study we wish to determine whether excess all-cause mor tality associated with smoking has increased during the last 20-30 yea rs in a study population representative of the general Danish populati on and whether any such changes relate to changes in smoking behaviour . Methods. Pooled data from three prospective population studies condu cted in Copenhagen with detailed information on smoking habits. A tota l of 31 194 subjects, 17 669 males and 13 525 females, initially exami ned between 1964 and 1992 with examinations repeated at intervals from 1-10 years, were followed until 1995 for all-cause mortality. Relativ e mortality risk in smokers versus never-smokers was calculated within periods of five calendar years and compared throughout the study peri od. Results. Male smokers' exposure did not change during the study pe riod whereas female smokers' exposure to tobacco increased in terms of age at smoking onset, quantity smoked and depth of inhalation. During follow-up 5744 males and 2900 females died. In males, death rate rati os (comparing continuous smokers with never-smokers) did not change in the study period. In females, ratios increased from 1964-1978 to 1979 -1994 by a factor of 1.3 (95% confidence interval 1.0-1.8). Conclusion s. In agreement with the observed changes in smoking habits, excess mo rtality in male smokers did not increase whereas excess mortality in f emale smokers increased slightly.