American journal of epidemiology
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The purpose of this study was to characterize the relation between smokeless tobacco use and the risk of all-cause and disease-specific mortality. Using data from the First National Health and Nutrition Examination Survey Epidemiologic Followup Study, the authors assessed the 20-year mortality experience of smokeless tobacco users. Subjects aged 45 years or more at baseline (1971-1975) were categorized as either smokeless tobacco users (n = 1,068) or non-smokeless tobacco users (n = 5,737). ⋯ The lung cancer mortality rate among combined users (smokeless tobacco and cigarettes), based on the rates for exclusive smokeless tobacco users and exclusive smokers, was higher than expected, possibly because of heavier smoking among these subjects. The mortality experience of smokeless tobacco users was not significantly greater than that of non-tobacco users and was appreciably less than that of cigarette smokers. Furthermore, combined use of smokeless tobacco and cigarettes did not increase overall mortality beyond that expected from use of the individual products.
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The authors examined the association between exposure to tobacco smoke in utero and the risk of stillbirth and infant death in a cohort of 25,102 singleton children of pregnant women scheduled to deliver at Aarhus University Hospital, Aarhus, Denmark, from September 1989 to August 1996. Exposure to tobacco smoke in utero was associated with an increased risk of stillbirth (odds ratio = 2.0, 95% confidence interval: 1.4, 2.9), and infant mortality was almost doubled in children born to women who had smoked during pregnancy compared with children of nonsmokers (odds ratio = 1.8, 95% confidence interval: 1.3, 2.6). ⋯ Conclusions were not changed after adjustment in a logistic regression model for the sex of the child; parity; or maternal age, height, weight, marital status, years of education, occupational status, and alcohol and caffeine intake during pregnancy. Approximately 25% of all stillbirths and 20% of all infant deaths in a population with 30% pregnant smokers could be avoided if all pregnant smokers stopped smoking by the sixteenth week of gestation.
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The area under the receiver operating characteristic curve is the most commonly used measure of the ability of a biomarker to distinguish between two populations. Some markers are subject to substantial measurement error. ⋯ A simulation study was used to check the validity of the proposed confidence interval. Furthermore, it was shown that not adjusting for measurement error could result in a serious understatement of the effectiveness of the biomarker.