Study: Four risk factors estimated to reduce life expectancy in the U.S.

A study published this week in PLoS Medicine finds that four risk factors - smoking, high blood pressure, high blood sugar and obesity - explain a substantial amount of the disparity in life expectancy amongst the "Eight Americas", which are groups of the US population that can be defined by race, and location and socioeconomic features of counties they live in. Together, these four risk factors are estimated to reduce life expectancy in the United States by 4.9 years in men and 4.1 years in women. The researchers calculate that disparities in life expectancy in the "Eight Americas" would decline by 20% if the four risk factors were reduced to optimal levels.

Smoking, high blood pressure, high blood sugar and obesity are preventable risk factors responsible for hundreds of thousands of deaths in the United States each year through chronic diseases such as cardiovascular diseases, cancers and diabetes. Goodarz Danaei (of the Harvard School of Public Health) and collaborators used information from national surveys to estimate the number of deaths that would have been prevented in 2005 if exposure to these four risk factors had been reduced. They estimated the effect of the risk factors on life expectancy in the United States as a whole, and also on the disparities in life expectancy and deaths from specific diseases among the "Eight Americas" that were observed in a previous study (http://dx.doi.org/10.1371/journal.pmed.0030260)

The researchers found that a person's ethnicity and where they live is a predictor of life expectancy and health. The Asian American subgroup had the lowest body mass index, smoking rates and blood sugar, whilst the white subgroups had the lowest blood pressure. Blood pressure was highest in the US black population, especially in the rural south; body mass index was highest in western Native American men and southern low-income rural black women; and smoking highest in western Native Americans and low-income whites in Appalachia and the Mississippi Valley. The effect on life expectancy of these factors was smallest in the Asian group and largest in low-income southern rural blacks.

Whilst acknowledging that other factors such as alcohol use and dietary salt are also major contributors to disease, the researchers emphasize that public health interventions to reduce smoking, high blood pressure, blood sugar and obesity must be implemented and evaluated to improve the nation's health and reduce health disparities in the United States.