In Montgomery County, Maryland, residents enjoy a life expectancy of 81.3 years(1). But less than one hour northeast, in Baltimore City, the life expectancy is about 68.6 years, nearly 10 years below the national average. It's a pattern that is being seen around the country--record-high longevity at one end of the spectrum, and mortality rates similar to those for low-income developing countries at the other.

In a new study researchers at HSPH, including lead author Christopher Murray and Majid Ezzati, argue that these observed disparities cannot be explained by race, income, or basic health-care access and utilization alone. Instead, chronic diseases, such as obesity, and injuries caused by well-established risk factors, such as alcohol, are major culprits.

The good news: Public health strategies that target certain populations with inexpensive, preventive interventions may narrow the gap, according to Murray, the Richard Saltonstall Professor of Population Policy and director of the Harvard Initiative for Global Health, and Ezzati, associate professor of international health.

Expanding on an earlier study on county mortality patterns, the HSPH team divided the U.S. population into eight large groups in terms of race as well as location and a select few sociodemographic characteristics of the counties in which people lived, such as degree of urbanization and income(2). An analysis of these subgroups reveals far greater inequalities in longevity and health than when only race is considered: In some cases, the gap between extremes is more than 15 years.

The researchers note that mortality disparities are most significant among the young (15-44 years of age) and the middle-aged (45-59 years of age), particularly for men. These findings demonstrate a need to widen the scope of government interventions in public health in terms of age groups served. Currently, the vast majority of such programs target children and the elderly.

For the full report, Eight Americas: Investigating Mortality Disparities across Races, Counties, and Race-Counties in the United States, see http://www.globalhealth.harvard.edu/Murrayetal-EightAmericas-PLoSMedicine2006_000.pdf.

Jesse Nankin is the development communications coordinator for the Office for Resource Development at HSPH.

Photograph: ©David Turnley/Corbis