A study led by researchers from the Harvard School of Public Health (HSPH) in collaboration with researchers from the Institute for Health Metrics and Evaluation at the University of Washington estimates that smoking, high blood pressure, elevated blood glucose and overweight and obesity currently reduce life expectancy in the United States by 4.9 years in men and 4.1 years in women.
The researchers also estimated the effects of these risk factors on eight subgroups of the U.S. population, called the “Eight Americas”. The “Eight Americas” are defined by race, county location and the socioeconomic features of each county. They found that these four risk factors account for a substantial proportion of differentials in life expectancy among these groups. Southern rural blacks had the largest reduction in life expectancy due to these risk factors (6.7 years for men and 5.7 years for women) and Asians the smallest reduction in life expectancy (4.1 years for men and 3.6 years for women).
“This study demonstrates the potential of disease prevention to not only improve health outcomes in the entire nation but also to reduce the disparities in life expectancy that we see in the United States,” Majid Ezzati, associate professor of international health at HSPH and senior author of the study, said in a news release.
The 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 a review of epidemiologic studies on the effects of these factors.
They estimated the number of deaths that would have been prevented in 2005 if exposure to the four risk factors had been reduced to their optimal levels or commonly used guidelines. They also assessed the benefits for life expectancy, a measure of longevity.
The researchers found that a person’s ethnicity and where they live is a predictor of life expectancy and how healthy a person is.
As a result, smoking, high blood pressure, elevated blood glucose and overweight and obesity account for almost 20% of disparities in life expectancy across the United States. These factors also accounted for 3/4 of disparities in cardiovascular mortality and up to half of disparities in cancer mortality.
Below is the number of years that would be gained in life expectancy in the United States if each individual risk factor was reduced to its optimal level:
- Blood pressure: 1.5 years (men), 1.6 years (women);
- Obesity (measured by body mass index): 1.3 years (men), 1.3 years (women);
- Blood glucose: 0.5 years (men), 0.3 years (women); and
- Smoking: 2.5 years (men), 1.8 years (women).