TOBACCO-RELATED MORTALITY

Of all the risks to human health, perhaps none has been studied as extensively as tobacco use. Claims about the hazards of smoking tobacco had been voiced for centuries prior to the first scientific studies on the extent of the risk in the early 1950s. Beginning with the pioneering work carried out in the United Kingdom by epidemiologists Richard Doll and Austin Bradford-Hill, cigarette smoking was first identified as a cause of lung cancer and, later, as a cause of numerous other cancers, as well as major respiratory and vascular diseases.

The evidence on causality for tobacco use as a cause of disease and death has become irrefutable. It has been firmly established in numerous case-control, as well as cohort, studies in several developed countries including the United Kingdom, the United States, Sweden, and Japan. Studies in China and India confirm that tobacco use in parts of the developing world is becoming an increasing health hazard in these populations.

In populations where smoking has been prevalent for decades, tobacco causes about 90 percent to 95 percent of lung cancer deaths, about two-thirds of upper aero-digestive tract cancers (and 40% to 50% of all cancer deaths), three-quarters of chronic bronchitis and emphysema deaths, and about one-fifth of all deaths from ischemic heart disease and stroke. Smokers typically have a 20- to 25-fold higher risk of lung cancer than non-smokers, and about a 3-fold higher risk of suffering a heart attack or stroke, compared with lifelong non-smokers. In younger smokers (less than 50 years of age), the risk of coronary heart disease or stroke is typically five to six times higher than in non-smokers. Overall, death rates for smokers are about 2.5 to three times higher than for non-smokers at all ages above 35 years.

The epidemiology of tobacco often leads to a serious misunderstanding of the full health effects of tobacco use. Most of the excess risk of diseases caused by tobacco only occurs several decades after persistent smoking has become widespread. This long delay between the uptake of tobacco use in a population and its full health effects can be misinterpreted to mean that tobacco is not a major cause of death. In developed countries, males began smoking in large numbers in the early decades of the twentieth century (a 60–70% prevalence of smokers among male adults was not uncommon), and by the early 1960s, cigarette consumption had peaked among men in these countries. However, mortality from tobacco use only began to rise beginning in the 1950s, increasing from an estimated annual death toll of about 300,000 in 1950 (20% of all deaths) to 1.45 million (28%) in 1995.

Women in developed countries began smoking much later than men, the practice being adopted first by women in Britain, the United States, Australia, Canada, and New Zealand in the 1930s and thereafter, and, since 1950, increasingly by women in Europe. Prevalence among women has become similar to that of men in these countries, but because they have been smoking for much shorter periods the full health effects are not yet evident. From causing virtually no deaths in 1950, tobacco in the early twenty-first century causes around 500,000 deaths annually among women in developed countries, half of these in the United States alone. This toll is expected to increase dramatically over the first and second decades of the twenty-first century as the impact of past consumption among women becomes apparent.

Overall, cigarette consumption in developed countries peaked in the 1980s and has been steadily declining at the rate of about 1.0 percent per year since then. Much of this decline can be attributed to the success of tobacco control measures taken by these countries, including bans or restrictions on advertising, restricting smoking in public places, increased taxation on cigarettes, banning vending machines for cigarettes, the inclusion of warning labels on cigarette packets, and public information campaigns. As a result, the annual toll of about 2 million deaths from tobacco use in these countries may not rise much higher. The effect of declining mortality among men will progressively outweigh the expected increases in female tobacco-caused deaths over the first two or three decades of the twenty-first century.

In developing countries, cigarette consumption has been relatively low, especially among women. However, smoking of either manufactured or homemade cigarettes has now become increasingly common in most developing countries: about half of all men are regular smokers, and about 10 percent of women. Hence, tobacco-related mortality, still comparatively low, can be expected to increase steeply. In China, where cigarette consumption has quadrupled since 1975, tobacco already causes about 1 million deaths annually. A comparable number (1 to 1.5 million) of deaths occur in the remainder of the developing world. If current trends continue, and cigarette consumption proves as hazardous in developing countries as elsewhere, tobacco use is projected to cause 10 million deaths per year by 2030, 7–8 million of which will be in developing countries. This would make tobacco use by far the greatest contributor to the burden of disease world-wide.

The reduction of cigarette smoking and other forms of tobacco use, particularly in developing countries, has become a global priority for public health action. The dramatic reductions in prevalence and consumption observed over several decades in many industrialized countries, most notably the United Kingdom, demonstrate that success is possible. Specific measures to curtail tobacco use such as advertising bans and price increases are likely to be much more effective in the context of strong political commitment to reducing consumption.

See also: Alcohol, Health Effects of; Cancer; Cardiovascular Disease; Disease, Burden of; Diseases, Chronic and Degenerative; Mortality Differentials, by Sex.

bibliography

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Liu, B. Q., R. Peto, Z. M. Chen, et al. 1998. "Emerging Tobacco Hazards in China: 1. Retrospective Proportional Mortality Study of One Million Deaths." British Medical Journal 317: 1411–1422.

Pampel, Fred C. 2002. "Cigarette Use and the Narrowing Sex Differential in Mortality." Population and Development Review 28: 77–104.

Peto, Richard, et al. 1994. Mortality from Smoking in Developed Countries, 1950–2000. Oxford: Oxford University Press.

Peto, Richard, and Alan D. Lopez. 2001. "Future World-wide Health Effects of Current Smoking Patterns." In Critical Issues in Global Health, ed. C. Everett Koop, C. E. Pearson, and M. Roy Schwarz. San Francisco: Wiley.

Alan D. Lopez