Data were from the 2007 NHIS, a cross-sectional household interview survey of the civilian, noninstitutionalized population in all 50 states and the District of Columbia that used a multistage area probability sampling design to produce nationally representative estimates on health. Data were collected through a household interview conducted by the US Census Bureau. All adults, aged 18 years and older, in a sampled household were invited to participate in the interview. One adult, aged 18 years or older, was randomly selected from the household for a survey of adult health. Responses were collected through computer-assisted personal interviewing.