Forecasting the Effects of Obesity and Smoking on U.S. Life Expectancy

Background: While increases in obesity over the past 30 years have adversely affected population health, there have been concomitant improvements due to reductions in smoking. Better understanding of the joint effects of these trends on longevity and quality of life will help policymakers target resources more efficiently. Methods: For each year from 2005 to 2020, we forecast life expectancy and qualityadjusted life expectancy for a representative 18 year old, assuming a continuation of past trends in smoking from the National Health Interview Survey (1978-79, 1990-91 and 2004-06), and past trends in body-mass index (BMI) from the National Health and Nutrition Examination Survey (1971-75, 1998-1994, and 2003-06). The 2003 Medical Expenditure Panel Survey was used to examine the effects of smoking and BMI on health-related quality of life. Results: The negative effects of increasing BMI overwhelmed the positive effects of declines in smoking in multiple scenarios. In the base case, increases in the remaining life expectancy of a typical 18 year old are held back by 0.71 years or 0.91 quality-adjusted years between 2005 and 2020. If all U.S. adults became normal weight non-smokers by 2020, LE is forecast to increase by 3.76 life years or 5.16 quality-adjusted years. Conclusions: If past obesity trends continue unchecked, the negative impact on U.S. population health is forecast to overtake the positive effect from declining smoking rates, which could erode the pattern of steady gains in health experienced since early in the 20th century.