The application of developments in theoretical biostatistics to epidemiologic research.
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Biomedical subjects
Publications and source records attributed to M Hjortland.
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Baseline 24-hour dietary recalls from 16,349 men ages 45-64 years who had no evidence of coronary heart disease (CHD) were obtained in three prospective studies: the Framingham Study (859 men), the Honolulu Heart Study (7272 men) and the Puerto Rico Heart Health Program (8218 men). These men were followed for up to 6 years for the first appearance of CHD or death. Men who had a greater caloric intake or a greater caloric intake per kilogram of body weight were less likely to develop CHD manifest as myocardial infarction (MI) or CHD death, even though men of greater weight were more likely to develop CHD. This may reflect the benefit of greater physical activity. Men who consumed more alcohol were less likely to develop CHD, but more likely to die of causes other than CHD, particularly in the Honolulu study. In the Honolulu and Puerto Rico studies, but not in the Framingham study, men who consumed more starch were less likely to develop MI or CHD death. There was an inverse relation between starch intake and serum cholesterol, but it was too weak to explain fully the inverse starch-CHD association. There was also no evidence that the inverse relation between starch intake and incidence of CHD in the Honolulu and Puerto Rico studies was an indirect result of differences in fat intake. While the findings suggest additional areas for research, none of them would lead to an alteration of currently recommended preventive diets that emphasize lowering fat intake, because in isocaloric diets the logical way to balance a decreased fat intake is to increase the consumption of foods containing starch.
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A standardized system for the collection and processing of dietary information in large-scale studies is described. Components of the system include interviewer and coder training, certification and continuing education, automated procedures for identifying and quantitating fat, guides for classifying and quantitating foods, system maintenance and quality control procedures, and a food table containing about 800 food items and 450 recipe items. The system is flexible enough to respond to market changes in formulation. Unique automated features make the system particularly useful in identifying and quantitating different dietary fats. These features could be modified to meet nutritional demands of other studies.
In the NHLI Twin Study MZ twins are shown to "get together" substantially more often than DZ twins. With this result as an indicator of differences in shared environment, the assumption of equal shared environmental variation for MZ and DZ twins is assessed using nutritional data calculated from a food frequency questionnaire. Six nutrients show significant genetic variance for the total sample. However, when stratified on the basis of how frequently twins see each other, none of the nutrients shows significant genetic variance for both strata. A similar pattern is seen for several individual items from the questionnaire. In addition, four of the nutrients show significant correlation between the absolute difference in the nutrient intake of MZ twin pairs and how often they "get together." These data appear to show that unequal environmental effects may lead to falsely high estimates of genetic variance for nutrient intake.
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