Large Epidemiologic Studies Re-examine Hazards of Smoking

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“Smokers lose at least one decade of life expectancy, as compared with those who have never smoked,” and the increased risk of death from cigarettes smoking “are now nearly identical for men and women,” according to two separate studies published online by TheNew England Journal of Medicine.

One study looked at smoking and smoking-cessation histories from 113,752 women and 88,496 men 25 years of age or older interviewed between 1997 and 2004 in the U.S. National Health Interview Survey and related these data to causes of deaths that occurred in 8,236 women and 7,479 men by December 31, 2006. For participants who were 25 to 79 years of age, the rate of death from any cause among current smokers was about three times that among those who had never smoked.

“Most of the excess mortality among smokers was due to neoplastic, vascular, respiratory, and other diseases that can be caused by smoking,” the researchers reported. “The probability of surviving from 25 to 79 years of age was about twice as great in those who had never smoked as in current smokers (70% vs 38% among women and 61% vs 26% among men). Life expectancy was shortened by more than 10 years among the current smokers, as compared with those who had never smoked,” they added.

“Adults who had quit smoking at 25 to 34, 35 to 44, or 45 to 54 years of age gained about 10, 9, and 6 years of life, respectively, as compared with those who continued to smoke,” the researchers reported. They noted, “the women in this cohort represent the first generation of women in the United States in which those who smoked began early in life and smoked for decades, and the risks of death for these women are about 50% greater than the risks reported in the 1980s studies.”

Second Study

That finding was corroborated by the other study, which measured 50-year trends in smoking-related mortality in the United States, and found that for women who were current smokers, compared to women who never smoked, the relative risks of death from lung cancer increased from 12.65 in the 1980s to 25.66 in the period from 2000 to 2010. The corresponding relative risk for males was almost the same—24.97.

Current male and female smokers “also had similar relative risks for death from chronic obstructive pulmonary disease (25.61 for men and 22.35 for women), ischemic heart disease (2.50 for men and 2.86 for women), any type of stroke (1.92 for men and 2.10 for women), and all causes combined (2.80 for men and 2.76 for women),” according to the study. “Among men 55 to 74 years of age and women 60 to 74 years of age, all-cause mortality was at least three times as high among current smokers as among those who had never smoked,” the study report continued.

Both reports stress the importance of smoking cessation efforts. “Our analyses of data from former smokers confirm that quitting smoking at any age dramatically lowers mortality from all major smoking-related diseases,” according to the analysis of 50-year trends in smoking-related mortality. Moreover, “nearly all the excess risk can be avoided if a person quits smoking before 40 years of age,” the authors pointed out.

“A focus on cessation of smoking is justified, since quitting smoking before the age of 40 years, and preferably much earlier, will reduce by about 90% the decade of life that is lost from continued smoking,” asserted the authors of the other study. ■

Jha P, et al: N Engl J Med. January 24, 2013 (early release online).

Thun MJ, et al: N Engl J Med. January 24, 2013 (early release online).