For decades, it has been widely known that smoking increases the risk for cancer. Most of us associate that risk with lung cancer in particular, but a new study indicates that smoking vastly increases deaths from all kinds of cancer, not just lung. And all of the subjects in the study were men. Guys, listen up. It's time to quit.
For almost a decade, scientists have relied on estimates that put the role of smoking in cancer deaths at around 34 percent. That is, of all cancer deaths, 34 percent could be attributed to smoking as a cause. That number looks to be changing, as a study by a University of California, Davis researcher, Bruce Leistikow, indicates that smoking is responsible for some 70 percent of cancer deaths. That's right—twice the existing estimate. In fact, among men aged 30 to 70, Leistikow's new epidemiological model has smoking implicated in 74 percent of deaths for 2003 even as, as he points out in the study, "Male lung and non-lung cancer death rates have declined steadily since 1992." (Globally, cancer is responsible for roughly one-third of total deaths.) This new number represents a truly an impressive change, and, if reliable, a wake-up call for smoking-prevention advocates. How did Leistikow and his co-authors arrive at this number?
Leistikow's study, published in the November 24 issue of BMC Cancer, was conducted using records of men aged 30 to 74 who died of cancer in Massachusetts between 1979 and 2003. This is a broad epidemiological study—but Leistikow's innovation lay in his development of a "smoke-load method" that can more accurately track the role of tobacco in cancer deaths. In part, his method excludes populations that have unusually high cancer deaths due to causes other than tobacco. These range from women who have had estrogen therapy, or a hysterectomy, to "historical changes in the classification of general causes of death". This is why the study was conducted using information about men in the 30 to 74 age group only, as they are the least affected by these population variations. In the end, Leistikow's study should give a neutral picture of cancer deaths from tobacco, all other things being equal, and should thus be generalizable to the population at large.
The study's conclusions are stark, and sharply stated: "The strong lung/non-lung cancer death rate associations suggest that tobacco smoke load may be responsible for most prematurely fatal cancers at both lung and non-lung sites." As a result of their new method, and its conclusions, the study's authors hope to see better and more aggressive anti-smoking measures at the level of public policy: "The improved ability to assess the population effect of tobacco smoke damage can be used to better inform cancer control policy including the regulation of tobacco products and smoking in public places." And, the hope is, that with such policy cancer deaths could not only continue to decline, but could do so more quickly. "The present method estimates are greater than the earlier estimates," the authors write. "Therefore, tobacco control may reduce cancer death rates more than previously noted." In other words, it just got even more important to quit smoking.