Women have caught up to men with regard to the risk of death from cigarette smoking, according to analyses of three study cohorts spanning multiple decades and hundreds of thousands of individuals. The risk of death among men has largely plateaued since the 1980s, though there has been an increase in mortality related to chronic obstructive pulmonary disease (COPD).
The new study’s authors, led by Michael J. Thun, MD, of the American Cancer Society in Atlanta, noted that smoking patterns have changed over several generations, which have altered the associated risks. “Daily cigarette consumption peaked during the 1970s among male smokers and during the 1980s among female smokers; smoking prevalence in the two groups has since decreased in parallel,” they wrote in the January 24 issue of the New England Journal of Medicine. “Women have more difficulty quitting than men; thus, for both current and former female smokers, the number of years of smoking has increased.”
The authors calculated death rates during three time periods: 1959–1965, 1982–1988, and 2000–2010, using two historical Cancer Prevention Study (CPS) cohorts and pooled data from five contemporary cohort studies. The CPS cohorts included 183,060 men and 335,922 women in the earlier study and 293,592 men and 452,893 women in the 1980s cohort. The pooled contemporary analysis involved cohorts ranging in size from about 33,000 men and 75,000 women up to more than 300,000 men and 200,000 women.
The relative risk of death from lung cancer for women who smoked vs those who did not increased across the three time periods, from 2.73, to 12.65, to 25.66 in the most recent period. In contrast, the relative risk for male smokers increased from 12.22 in the earliest period to 23.81 in the 1980s, but stayed relatively stable to the 2000s, when it reached 24.97.
In the modern cohorts, the relative risks of death from COPD were similar for men (25.61) and women (22.35) vs nonsmokers; this was also the case for relative risks of ischemic heart disease (2.5 for men and 2.86 for women), stroke (1.92 for men and 2.1 for women), and all-cause mortality (2.8 for male smokers and 2.76 for female smokers). The relative risk of death from COPD rose sharply among male smokers, from the 1980s period (9.98) to the contemporary period, in contrast to the relatively stable lung cancer mortality risk.
The authors wrote that the similar risks for men and women is a new finding and “confirms the prediction that, in relative terms, ‘women who smoke like men die like men.’” The convergence of risk reflects a convergence of smoking patterns, they noted, and added that quitting smoking by the age of 40 would ensure nearly all excess mortality risk to be avoided.
In an accompanying editorial in the New England Journal of Medicine, Steven A. Schroeder, MD, of the University of California, San Francisco, wrote that cohort studies such as this capture trends “but omit nuances.” Among those omissions is a lack of data on frequency of smoking, an important point since an increasing proportion of smokers are light smokers. The cohorts featured also overrepresented people who were better educated, reflected in lower overall smoking rates than the general population.
“The importance of smoking as a health hazard needs to be elevated,” Schroeder wrote. “More women die of lung cancer than of breast cancer. But there is no ‘race for the cure’ for lung cancer, no brown ribbon…. The need for greater attention to the policies known to reduce the prevalence of smoking remains urgent.”