The promise of prevention: the effects of four preventable risk factors on national life expectancy and life expectancy disparities by race and county in the United States
Published in PLoS Medicine, March 2010
Life expectancy in the US is shortened by more than four years because of preventable risk factors such as smoking and being overweight, IHME researchers found. The study, The promise of prevention: the effects of four preventable risk factors on national life expectancy and life expectancy disparities by race and county in the United States, is the first nationwide study to look at the effects on life expectancy of smoking, high blood pressure, high blood glucose, and being overweight.
When looking at eight subgroups of the US population – known as the Eight Americas – researchers found that smoking, high blood pressure, high blood glucose, and being overweight account for 20% of the disparities in health outcomes overall. These four factors also accounted for three-quarters of disparities in cardiovascular mortality and up to half of disparities in cancer mortality.
The Eight Americas are defined by race, county location, and the socioeconomic features of each county. Southern rural blacks had the largest loss of life expectancy due to these risk factors at 6.7 years for men and 5.7 years for women. Asians had the smallest drop in life expectancy – 4.1 years for men and 3.6 years for women.
Within the Eight Americas subgroups, researchers found that ethnicity and where people live are predictors of life expectancy and of specific risk factors:
- Asian American men and women had the lowest body mass index (BMI), blood glucose levels, and prevalence of smoking.
- Blacks, especially those in the rural South, had the highest blood pressure.
- Whites had the lowest blood pressure.
- Western Native American men and Southern low-income rural black women had the highest BMI.
- Western Native American and low-income whites in Appalachia and the Mississippi Valley had the highest prevalence of smoking.
Researchers used 2005 data from the National Center for Health Statistics, the National Health and Nutrition Examination Survey, the Behavioral Risk Factor Surveillance System, and an extensive review of epidemiologic studies on the effects of these factors. They used epidemiologic methods for multiple risk factors to estimate the effects of current exposure to these risk factors on death rates and life table methods to estimate effects on life expectancy.
There has been substantial research on psychosocial and health care determinants of health disparities in the US but less on the role of modifiable risk factors. This study estimates the effects of smoking, high blood pressure, elevated blood glucose, and adiposity on national life expectancy and on disparities in life expectancy and disease-specific mortality among eight subgroups of the US population (the Eight Americas) defined on the basis of race and the location and socioeconomic characteristics of county of residence in 2005. This research is part of ongoing work by IHME to gauge how societies are performing in addressing health challenges locally and internationally.
Recommendations for future work
This study examined disparities in four preventable risk factors among US racial and geographical subgroups, and how they explain a substantial proportion of the disparities in deaths from cardiovascular diseases, diabetes, and cancers among these subgroups. The disparities in risk factor exposure also explain some of the disparities in life expectancy. One limitation to this study is that the effects of other disparities in deaths and life expectancy that could be the result of preventable risk factors (such as dietary fat, alcohol use, and dietary salt, which are major contributors to different diseases) were not included in this study. Reduced exposure to preventable risk factors through the implementation of relevant policies and programs should reduce life expectancy and mortality disparities in the US and yield health benefits at a national scale.
Future research should focus on how to use disease prevention to improve health and reduce health disparities together with policies that aim to reduce socioeconomic disparities, reform health care, and improve quality of care. We should identify, implement, and rigorously evaluate effective population-based and personal interventions that can reduce these preventable risk factors or mitigate their effects on disease outcomes.
Citation: Danaei G, Rimm EB, Oza S, Kulkarni C, Murray CJL, Ezzati M. The promise of prevention: the effects of four preventable risk factors on national life expectancy and life expectancy disparities by race and county in the United States. PLoS Medicine. 2010 Mar 23; 7(3):e1000248.