During most of the 20th century, the disease risks from cigarette smoking became evident, first among male smokers and later among female smokers. Before World War II, relatively few women smoked regularly. Daily consumption of cigarettes peaked during the 1970s in male smokers and during the 1980s in female smokers. In both males and females, the average age of initiating smoking decreased over time.
This study was designed to determine whether the risks of smoking have continued to increase during the past 20 years. As the lifetime smoking behaviors of males and females have become increasingly similar, a central question addressed in this article is whether the hazards for women are now approaching those for men. The investigators examined temporal trends in mortality among smokers across 3 time periods (1959–1965, 1982–1988, and 2000–2010); absolute and relative risks among smokers were compared according to sex and self-reported smoking status in 2 historical cohort studies and in 5 pooled contemporary cohort studies in the United States. All participants attained an age 55 years or older during follow-up. The relative risk of death for the 3 time periods was estimated for the most common diseases related to smoking (lung cancer, chronic obstructive pulmonary disease [COPD], ischemic heart disease, any type of stroke) and for all causes combined. The age-adjusted and multivariable-adjusted relative-risk estimates were calculated using Cox proportional hazards regression, according to the intensity and duration of smoking among current smokers and the age at the time of quitting among former smokers.
In the 1960s and 1980s, the relative risk of death from lung cancer increased from 12.22 to 23.81 in men and from 2.73 to 12.65 in women. In the contemporary cohort, the risk of death from lung cancer was almost identical in men and women: 24.97 (95% CI, 22.20–28.09) and 25.66 (95% CI, 23.17–28.40), respectively. The risks for death in the contemporary cohorts were also similar in male and female current smokers for the following: COPD (25.61 for men and 22.35 for women), ischemic heart disease (2.50 for men and 2.86 for women), stroke (1.92 for men and 2.10 for women), and all causes combined (2.80 for men and 2.76 for women). Among male smokers, mortality from COPD continued to increase in the contemporary cohorts in nearly all the age groups and within each stratum of intensity and duration of smoking. All-cause mortality in men 55 to 74 years of age and women 60 to 74 years of age was at least 3 times higher among current smokers than in those who have never smoked. Mortality from all major smoking-related diseases was dramatically reduced by quitting smoking at any age.
These data show a persistent increase in the risks of smoking-related deaths among female cigarette smokers over the past half century. The risks for women now equal those for men. Among both sexes, risks are much higher in smokers compared with individuals who have never smoked. The risks among male smokers have plateaued at the high levels observed in the 1980s, with the exception of a continuing, unexplained increase in deaths from COPD.
Department of Epidemiology (M.J.T., B.D.C., S.M.G.), American Cancer Society, Atlanta, GA; Channing Division of Network Medicine (D.F.), Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA; the Division of Cancer Epidemiology and Genetics (N.D.F., P.H.), National Cancer Institute, Bethesda, MD; the Division of Public Health Sciences (R.P.), Fred Hutchison Cancer Research Center, Seattle, WA; and the School of Population Health (A.D.L.), University of Queensland, Brisbane, Australia