Chronic obstructive pulmonary disease (COPD) morbidity and mortality are rising, a trend that is unique among the top five causes of death in the USA. Despite the enormity of the problem, there are relatively few epidemiologic studies on COPD risk factors besides cigarette smoking. The proposed study examines the relationship between dietary factors and COPD among participants in the Nurses' Health Study, an ongoing prospective cohort study of 121,700 women, ages 39-64 in 1985. This cohort has been followed by means of biennial questionnaires which inquire about a variety of topics, including dietary intake (using a validated semi-quantitative food frequency questionnaire) and physician diagnosis of COPD. In 1998, all participants with a history of COPD were sent a supplementary questionnaire regarding specifics of COPD diagnosis and related topics. The primary aim of the proposed study will be to examine the relation of dietary factors to risk of newly-diagnosed COPD during 1985-1998. During this time period, there were approximately 2,100 cases of """"""""confirmed"""""""" COPD (i.e., physician diagnosis and pulmonary function tests [PFTs] at time of diagnosis or abnormal FEV-1 in past year) and """"""""probable"""""""" COPD (i.e., physician diagnosis and recent respiratory symptoms, but PFTsnot known). Preliminary data support the validity of these case definitions, and this will be examined further by reviewing 600 medical records. Likewise, potential under-diagnosis will be examined in a random sample of past and current smokers who have never reported COPD or asthma. The specific dietary hypotheses are that high intakes of antioxidants (e.g., vitamin C, vitamin E, and carotenoids), magnesium, potassium, and n-3 polyunsaturated fatty acids (e.g., fish oils) decrease risk of COPD, whereas high intakes of specific fatty acids (e.g., linoleic acid) increase risk. The cohort size and 13-year follow-up provide greater than 90 percent power to detect a trend across quintiles of dietary intake. In 1998, among approximately 2,400 prevalent cases with diet data, study investigators will address a secondary aim: to determine the relation of dietary factors to COPD severity during 1998-2000. COPD severity will be assessed by self-report of current medications, recent symptoms, activity limitations, and health care utilization (e.g., emergency room or urgent office visits for COPD exacerbations). The rising prevalence of COPD, particularly among women, along with its high societal cost, make COPD 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 COPD.
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