If we were asked to name the leading causes of death, most of us would name cardivascular disease and cancer. These are indeed the primary pathophysiological conditions identified at the time of death, but they are not the root causes. Diseases are the result of a combination of (unmodifiable) genetic and (modifiable) lifestyle factors. The real question therefore is what factors make the most significant contributions to these and other diseases.

A 1993 paper (1) attempted to answer that question. The authors searched the scientific literature from 1977 to 1993 for articles that quantitatively related lifestyle factors with disease. Coupled with actual U.S. death rates for 1990, they arrived at the following table of top risk factors and associated death tolls:

1. tobacco 400,000
2. diet/activity patterns 300,000
3. alcohol 100,000
4. microbial agents 90,000
5. toxic agents 60,000
6. firearms 35,000
7. sexual behavior 30,000
8. motor vehicules 25,000
9. illicit drug use 20,000

These ten factors (poor diet and sedentary lifestyle were lumped together) were estimated to account for about 50% of all U.S. deaths in 1990. Smoking, bad diets and lack of exercise are seen to be by far the major problems, accounting for 19% and 14% of all deaths, respectively.

The authors of a 2004 paper (2) put the U.S. death toll from smoking and poor diet/physical inactivity, the leading causes of death in the 1993 article, at 430,000 and 400,000, respectively. Their estimates are based on a survey of the relevant literature from 1980 to 2002 and actual numbers of U.S. deaths in 2000. As these authors point out, poor diet and lack of physical activity may soon overtake smoking as the leading cause of death in the United States.

The authors of a 2009 paper (3) analyzed data from the Potsdam, Germany, segment of the multi-center European Prospective Investigation Into Cancer (EPIC-Potsdam) study to estimate the risks associated with smoking, poor diet, lack of physical activity and high body mass index (a rather strange choice, given its dependence on diet and activity level). People who had none of these risk factors turned out to be 78% less likely to develop any chronic disease compared to those who smoked, ate poorly, were inactive and too heavy. Specific risk reductions were estimated to be 93% for diabetes, 81% for heart attacks, 50% for stroke, and 36% for cancer.

The authors of these papers emphasize that their numbers are only rough estimates of the death toll from perfectly avoidable risks. But these figures show very convincingly just how many of our chronic health problems are self-inflicted.

Sources

1. McGinnis JM, Foege WH. Actual causes of death in the United States. JAMA 1993;270(18):2207-2212.
   http://jama.ama-assn.org/cgi/reprint/270/18/2207
2. Mokdad AH, Marks JS, Stroup DF, Gerberding JL. Actual causes of death in the United States, 2000. JAMA 2004;291:1238-1245.
   http://jama.ama-assn.org/cgi/content/abstract/291/10/1238 [Free Abstract]
3. Ford ES, Bergmann MM, Kröger J, Schienkiewitz A, Weikert C, Boeing H. Healthy living is the best revenge. Findings from the European Prospective Investigation Into Cancer and Nutrition - Potsdam Study. Arch Intern Med 2009;169:1355-1362.
   http://archinte.ama-assn.org/cgi/reprint/169/15/1355