Data from this study were from the National Health and Nutrition Examination Study,
a cross-sectional health interview survey representative of the U.S. civilian, noninstitutionalized population.
For their study, the researchers compared data from the 2003 National
Health Interview Survey (NHIS), a
cross-sectional survey of U.S. households conducted by the U.S. Centers for Disease Control and Prevention's National Center for
Health Statistics, with data from a smaller survey of 628 African - American and non-Hispanic white men living in Baltimore.