Clinical characteristics of the study population.

a% (n/ntotal).
bgeometric mean (95% prediction interval).
BMI, body mass index.
†Social class were defined in 5 categories based on employment status and years of education.
††A history of chronic disease was defined as a positive answer to questions regarding physician diagnosed diabetes, hypertension, cerebrovascular disease, ischemic heart disease, and other cardiac diseases.
†††Atopy was defined as a positive test for specific IgE to at least one of four common inhalant allergens.