Descriptive information of the US study population by country of origin1.

1Country of origin is country of birth, except for second generation migrants where it is the country of birth of the parents.2Education: Low = no higher than ‘12th grade without diploma’, Middle = from ‘high school diploma or equivalent’ to ‘college but no degree’, High = from ‘associate degree’ to ‘doctorate degree’.32nd Generation: those born in the US whose parents are both foreign-born.*Other Africa: Ghana, Kenya and South Africa.