In 1964 the U.S. Surgeon General Report provided the first warning that smoking has adverse health effects. This statement has had a profound impact on both our society and our health care system. Despite this warning, many have continued to smoke over the past 50 years. Now, with 50 years of data from long time smokers, those who quit smoking at various points, and large numbers of male and female smokers, two articles in this week’s NEJM report on trends that have come out of this massive amount of data. These show the continued large negative impact that smoking has on health.
In one article, Thun et al. compare rates of mortality due to smoking in three separate time periods (1959-65, 1982-88, and 2000-2010). For the contemporary cohort, they analyze five large study populations. The authors find that being a current smoker vs. never having smoked increased the standardized relative risks (RR) of mortality from all causes by just less than 3 fold in males and in females. In addition, rates of death related to lung cancer increased in female smokers across all three time periods, and increased in men during the first two time periods before stabilizing since the 1980s. The RR for all cardiovascular causes increased in current smokers over time.
Interestingly, the mortality rate from COPD in female non-smokers remained constant over the three time periods but decreased in men. In contrast, the COPD mortality rates increased across all three time periods in both male and female smokers. This indicates an increase in COPD mortality rate in male smokers over time (in contrast to lung cancer rates). The authors attribute this difference to a change in the design of cigarettes, which encourage deeper inhalation and thus more damage to lung parenchyma. This may have also affected the distribution of lung tumors associated with smoking, which moved from more proximal to more distal areas of the lungs.
Importantly, Thun et al. show that, although earlier studies found a difference in health effects of smoking between male and female smokers, over time, as more women have begun to smoke and have started to smoke more, the smoking related deaths in women have begun to approach those in men. Thus, they conclude, “women who smoke like men, die like men.”
Thun et al. also show that quitting smoking at any time can have substantial health benefits. Jha et al. expand on this notion in another article this week in NEJM, in which they analyze a cohort of 113,752 females and 88,946 males interviewed from 1997-2004, and whose deaths were reported by 2006. Similar to Thun et al., the authors find an all-cause mortality hazard ratio of about 3 in both males and females when comparing current to never smokers—adjusting for alcohol use, education, and adiposity had little effect on these values. On average, current female and male smokers have their lives cut by about 11 years and 12 years, respectively, compared to never smokers. Quitting between ages 25-34 allowed former smokers to gain about 10 years of life, and the survival curve was nearly identical to that of never smokers. Those who quit at ages 35-44 years gained about 9 years of life and avoided nearly 90% of the adverse health effects of smoking. Cessation at later ages had some health benefits as well: quitting before age 50 allowed for a gain of about 6 years of life.
In an accompanying editorial, Steven Schroeder, M.D., points out two important conclusions. First, smoking cessation can have major positive impacts on health. As physicians, we should encourage and help our patients to quit smoking at any age, given the serious health benefits. In addition, Schroeder says that, although we’ve known for 50 years that smoking has adverse health effects, we have underestimated the impact of smoking on health. Thus, greater attention should be paid to the impact that smoking is having on the health of our society, especially in those of lower socio-economic status who are continuing to smoke at higher rates.