2.5. Mothers’ Characteristics
asthma
HAY FEVER, ASTHMA
The stool and blood samples were collected at three different sites: Boston, MA; San Diego, CA; and St. Louis, MO. The available subjects’ characteristics from the initial enrollment questionnaire are the mothers’ age, race, education, household income, and history of asthma and hay fever. Mothers were categorized into groups for each factor, except for their age, which was kept as a continuous variable. Race and ethnicity information was collected, because they are determinants of the circulating 25-hydroxyvitamin D levels; the race and ethnicity of every participant was self-reported. Participants were asked to first categorize themselves as either Hispanic or non-Hispanic, then to categorize their race into prespecified categories. Race/ethnicity (called race hereafter) groups were collapsed into 3 groups for the analysis: Black or African American mothers (called Black mothers hereafter), White, non-Hispanic mothers (called White mothers hereafter), and Hispanic mothers and mothers of other races (