Asthma prevalence continues to rise without satisfactory explanation; national surveys now estimate that at least 8% of Americans have this chronic disease. Although anti-inflammatory medications have proven effective for decreasing exacerbations, there are few options for primary prevention. The proposed study examines the relationship between modifiable dietary factors and risk of developing asthma among participants in the Growing Up Today Study, an ongoing prospective cohort study of 16,539 boys and girls, ages 9-14 in 1996, and children of registered nurses. This cohort is followed by annual questionnaires that inquire about a variety of topics, including dietary intake (using a validated semi-quantitative food frequency questionnaire), physical activity, height, weight, and physician diagnosis of asthma. The primary aim of the proposed study will be to examine the relation of dietary factors to risk of incident asthma during 1996-1999. The specific hypotheses are that high intakes of antioxidants (e.g., vitamin C, vitamin E, and carotenoids), n-3 polyunsaturated fatty acids (e.g., fish oils), and vitamin D decrease risk of asthma. Moreover, we hypothesize that body mass index (BMI) increases asthma risk in both boys and girls, independent of diet or physical activity level. During the 3-year follow-up period, there were approximately 1,020 cases of doctor-diagnosed asthma. Preliminary data support the validity of these incident cases, but validation studies are needed. We propose to send all children with incident asthma an asthma questionnaire to confirm their self-report of doctor-diagnosed asthma. A 20% random sample (n=204) will undergo chart review to further validate the diagnosis; the chart review will focus on doctors' notes, pulmonary function tests, and documented exacerbations. The asthma questionnaire also will be sent to mothers of children who undergo chart review to further corroborate disease-related data. To address potential concerns about under-diagnosis of asthma, we also will survey a 2% random sample of the all non-asthmatic children. These 265 non-asthmatic children, and their nurse mothers, will be asked about childhood allergies and asthma-like symptoms. Taken together, the validation studies will permit the creation of a large and methodologically sound asthma dataset with which to examine the specific aims listed above. The cohort size provides >90% power to detect trends across quintiles of dietary intake, physical activity, and BMI. The rising prevalence of asthma, along with its high societal cost, make asthma prevention an important public health goal. The proposed study is cost-effective, as it makes use of an existing cohort, and it will provide information that could have direct clinical application to reduce risk of asthma. ? ? ? ?
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