WEDNESDAY, December 2, 2009 (Health.com) — Although fewer people are smoking—and therefore less likely to die from cigarette-related causes—the obesity epidemic may negate any gains in life span, according to a new study.
By 2020, the typical 18-year-old will gain 0.31 years due to the drop in smoking rates (above and beyond life span increases caused by other factors). But the increase in obesity rates during the same period will reduce life expectancy by 1.02 years, the researchers say.
During the next 10 years, in other words, we’ll lose 0.71 years of our life span, time that we would have gained if so many people weren’t overweight, according to the estimates published this week in the New England Journal of Medicine (NEJM).
In addition, the increase in quality-adjusted life expectancy—a measure that takes into account levels of disability and other quality-of-life factors—will be reduced by 1.32 years. If all U.S. adults were nonsmokers of normal weight, life expectancy would increase by 3.76 years, or 5.16 quality-adjusted years, according to the study.
“Life expectancy is not going to decline,” says the study’s lead author, Susan T. Stewart, PhD, a researcher at the National Bureau of Economic Research, in Cambridge, Mass. “But it could have risen by that much more if it weren’t for the increases in obesity.”
Stewart and her colleagues forecast life expectancy through the year 2020 using national survey data. Smoking, a major risk factor for lung disease, heart disease, and cancer, has decreased by 20% in the United States in the past 15 years, according to the study.
Over the same period, obesity has increased by 48%. Obesity contributes to a host of serious health problems, including heart disease, diabetes, joint problems, stroke, and some sleep disorders.
By 2020, the report predicts, smoking will decrease by 21%, but 45% of the population will be obese.
Prior research has examined the effects of obesity on longevity, but this study is the first to examine the combined effects of obesity and smoking.
“No one ever has really done quite this linkage between smoking and obesity,” says S. Jay Olshansky, PhD, a professor of epidemiology and biostatistics at the School of Public Health at the University of Illinois at Chicago. “Some people have suggested we’re on the verge of dramatic increases in life expectancy because of reductions in smoking, but these authors are saying, ‘Hold on a minute; the negative effect of obesity is much greater.’”
Next page: Study should be a wake-up call
