Obesity Impacting Life Expectancy

The National Academy of Sciences has reported a slowdown in mortality improvement rates in the United States compared to other countries, and studies indicate that a major contributor is the rise in the prevalence of obesity. 

Rising body mass index (BMI) in the United States has reduced the annual rate of improvement in death rates between 1988 and 2011 by more than half a percentage point. This is the equivalent to 23% relative reduction in the rate of mortality decline. In 2011, the increase in BMI reduced life expectancy at age 40 by 0.9 years and contributed to 186,000 additional deaths. These data were analyzed from the National Health and Nutrition Examination Survey using Cox models to compare mortality trends in the presence and absence of adjustment for maximum lifetime BMI.  Between the years of 1988-1994 and 2005-2010, the proportion of the U.S. adult population (ages 40-79 years) that had been obese at some point in their lives increased from 40 to 52%. The age-standardized prevalence of obesity in adults based on height and weight increased from 15% in the 1970s to 38% in 2014.

Obesity is associated with diabetes, cardiovascular disease, cancer, and all-cause mortality. The death rates from cardiovascular disease that have declined for close to four decades in the U.S. have come to a halt. Compared to 13 other countries, the death rates from heart disease in the U.S. at ages 50-54 declined at a slower rate between 1999 and 2015.

Other causes of death contributing to the decline in mortality improvement include accidental poisoning linked to the epidemic of opioid use, suicide, and chronic liver disease. After adjusting for these, the trend persists, suggesting these causes do not provide a complete explanation for the slowdown.

The negative effects of increasing levels of BMI have worked against the positive benefits we have reaped from reducing tobacco use and advancing medical technology. If the trend of higher BMI continues, it will jeopardize future gains in life expectancy in the United States.

References:

• Institute of Medicine and National Research Council (2013) U.S. Health in International Perspective: Shorter Lives, Poorer Health (The National Academies Press, Washington, DC).
• National Research Council (2011) Explaining Divergent Levels of Longevity in High-Income Countries (The National Academies Press, Washington, DC)
• Flegal KM, Carroll MD, Kit BK, Ogden CL (2012) Prevalence of obesity and trends in the distribution of body mass index among US adults, 1999-2010. JAMA 307:491–497
• Lloyd-Jones DM (2016) Slowing progress in cardiovascular mortality rates: You reap what you sow. JAMA Cardiol 1:599–600.