Obesity to Overtake Smoking as Leading Cause of Death

Tobacco use continues to be the underlying cause of the greatest number of deaths in the United States, according to an analysis of actual causes of death by researchers at the CDC. However, poor diet/ lack of physical activity, currently ranked number 2, is expected to surpass smoking as the prevailing underlying cause of death by 2005.

Tobacco use was linked to 435,000 deaths in 2000 or 18.1% of total deaths. Poor diet/physical inactivity accounted for 400,000 deaths, or 16.6% of deaths, in 2000 (Cover Figure).

While smoking rates have dropped in recent years, obesity is on the rise. Currently, nearly 65% of Americans are overweight. From 1990 to 2000, the number of deaths attributed to poor diet/physical inactivity increased markedly in both absolute and relative terms, from 300,000 to 400,000 deaths and from 14% to 16.6% of total deaths. Although the number of deaths caused by smoking also increased from 1990 to 2000, the increase was slight, up 35,000 from 400,000 in 1990 (the increase can be attributed to the inclusion of deaths caused by secondhand smoke and infant deaths caused by maternal smoking, which were not reflected in the 1990 data).

Despite the increase in the number of smoking-related deaths, the percentage of deaths linked to tobacco use declined nearly 1 percentage point, from 19% of all deaths in 1990. Actual causes of death are defined as lifestyle and behavior that contribute to the reported causes of death, with heart disease, cancer, and stroke topping the list of reported causes (Figure).

The 9 leading reported causes of death in the United States account for approximately three quarters of all deaths. (From Minino AM et al. Natl Vital Stat Rep. 2002;50:1-120; Mokdad AH et al. JAMA. 2004;291:1238-1245.)

Findings of the study, led by Ali H. Mokdad, PhD, of the National Center for Chronic Disease Prevention and Health Promotion, were published in the March 10 issue of the Journal of the American Medical Association. The CDC researchers reviewed approximately 1000 studies linking selected behaviors with death and then used a formula to determine actual risk from the behaviors.

"The most striking finding was the substantial increase in the number of estimated deaths attributable to poor diet and physical inactivity," the researchers wrote. "The gap between deaths due to poor diet and physical inactivity and those due to smoking has narrowed substantially." They warned, "It is clear that if the increasing trend of overweight is not reversed over the next few years, poor diet and physical inactivity will likely overtake tobacco as the leading preventable cause of mortality." The researchers called for interventions to prevent and increase smoking cessation rates, improve diet, and increase physical activity to "become much higher priorities in the public health and health care systems."

About half of all deaths that occurred in the United States in 2000 can be attributed to largely preventable behaviors and exposures. There were some positive developments since 1990. In addition to the decline in relative numbers of deaths for tobacco use, both absolute and relative numbers of deaths declined for alcohol consumption, 100,000 to 85,000; microbial agents (eg, influenza, pneumonia), 90,000 to 75,000; toxic agents (eg, pollutants, asbestos), 60,000 to 55,000; firearms, 35,000 to 29,000; sexual behavior, 30,000 to 20,000; and illicit drug use, 20,000 to 17,000 (Cover Figure). However, these modest declines were largely overshadowed by the increasing rate of obesity attributed to poor diet/physical inactivity and subsequent implications for future morbidity and mortality. The number and percentage of motor vehicle–related deaths also increased, from 25,000 to 43,000.

The increasing rate of obesity also has significant cost implications. In a study published in the March/ April issue of Health Affairs, Roland Sturm, PhD, and colleagues at RAND, predict an increase of 18% to 22% in the number of persons aged 50 to 69 years who experience difficulty in bathing, dressing, or walking across a room because of health problems caused by rising rates of obesity by 2020. Sturm and colleagues also expect the percentage of older men and women reporting poor or fair health to increase by 12% to 14% because of health problems linked to obesity. Moderately obese men in the study were 50% more likely to experience at least some limitation in their daily activities; for women, the probability of limited activity doubled. The researchers calculate that health care costs are 44% higher among moderately and severely obese older persons than for persons at normal weights.

The Department of Health and Human Services said on March 9 that it will fund new obesity research and begin running public service ads on the importance of controlling weight.

Data for the Cover Figure and in "Trend of the Month" are from the Centers for Disease Control and Prevention. More information is available on the CDC Web site: www.cdc.gov.


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