摘要:

Several authors have used Popper's “white swan” example to support arguments for a falsificationist approach to epidemiology. The statement “all swans are white” cannot be verified by finding even a large number of white swans, but can be falsified by finding a single black swan. An analogous epidemiologic example that has been proposed is the hypothesis that a particular virus is a necessary cause of acquired immunodeficiency syndrome (AIDS). Such examples, however, have little relevance to science since scientific theories are not generalizations of facts; rather, they involve an understanding of the underlying processes that cause certain facts to occur. Futhermore, the “white swan” example is particularly inapplicable to epidemiology, since most factors of scientific or public health importance are neither necessary nor sufficient causes of disease. Nevertheless, epidemiologic research has achieved success in the understanding and prevention of disease. These points are exemplified by applying Rothman's model of causal constellations, which provides a conceptual basis for the development of epidemiologic theories.

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Exposure misclassification is a well-known problem in epidemiologic studies and can considerably dilute relative risk (RR) measures toward unity. A vivid illustration of such misclassification occurs in familial aggregation studies, where “exposure” is defined as a specified genetic relationship to an affected individual (case) or to an unaffected individual (control). Even in the simplest single-gene model, only a fraction of relatives of cases have the disease genotype. Also, if the trait is not fully penetrant, a proportion of relatives of controls can have the genotype. Thus the familial RR measures are subject to misclassification bias if they are interpreted as the relative eftect of a susceptible genotype. The effects of this form of “exposure” (or more properly genotype) misclassification on familial RR measures were quantified and applied empirically to known disease-genetic trait associations. Expected RRs in first-, second-, and third-degree relatives were generated and plotted for different genotype RRs, disease, and allele frequencies. In general, familial RRs are substantially lower than genotypic RRs. Even in the case of strong associations such as HLA-B27 and ankylosing spondylitis (RR = 100), RR measures in first-, second-, and third-degree relatives are only 6.0, 3.5, and 2.2, respectively. Such strong misclassification effects may result in considerable reduction of statistical power in family studies. It is suggested that etiologic studies of disease explore directly the role of measurable genetic traits in epidemiologic studies in populations as well as in families.

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

A reduced questionnaire was developed by successively omitting segments of the full (98-item) Block questionnaire and calculating the correlations between nutrient estimates produced by the full and reduced versions. The reduced version contains 60 food items and requires 17 minutes to administer by an interviewer. It is intended to capture all nutrients in the diet, as is the full version. The reduced version was validated against three four-day records in a group of middle-aged women, and against two seven-day records collected 10–15 years ago in a group of older men. The absolute value of macronutrients estimated by the reduced questionnaire was lower than food-record estimates, but most micronutrients were not underestimated. For macronutrients correlations with food records were slightly lower with the reduced questionnaire, but for micronutrients there was only slight or no reduction in correlations as a result of using the reduced version. The brief version may be useful in studies that cannot allow the 30–35 minutes required for the full-length questionnaire.

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Several questionnaires are available for assessing physical activity, but few of these instruments have been validated, particularly with respect to energy balance. Twenty-one healthy men 28–55 years old participating in a free-living, controlled feeding experiment completed eight widely used physical activity questionnaires. These were compared with measured caloric intake and resting energy expenditure during a period of stable body weight. Physical activity indices or daily energy expenditure estimates derived from the questionnaires generally increased with energy intake. The questionnaires were moderately well correlated with each other: interquestionnaire correlation coefficients ranged from 0.09 to 0.81 (median = 0.53). Correlations between the questionnaires and energy intake, which ranged from 0.13 for the Minnesota Leisure Time Activity instrument to 0.49 for the Harvard Alumni questionnaire, were higher than between the questionnaires and nonresting energy expenditure; that is, energy intake minus resting energy expenditure (correlation coefficient range 0.05–0.32). The Five-City Project questionnaire yielded an average estimate of total caloric expenditure that most closely approximated intake (96%). These data indicate that although estimates of individual energy expenditure or physical activity may be less than optimal, most of the questionnaires evaluated provide reasonable group means for these parameters.

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

We conducted a pilot study to determine the most efficient mailing strategy for a postal questionnaire study among nurses in Ontario, Canada. Five mailing strategies involving types of stamps on the return envelopes were considered: no stamp, business-reply stamp, metered stamp, small regular stamp, and large commemorative stamp. We found that paper stamps, especially large commemorative stamps, on return envelopes increased the response rate and reduced the response time, as compared with other mailing strategies. Business-reply stamps had the lowest cost per response received and a low total cost.

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

A rapidly converging algorithm is given to calculate exact confidence intervals about the adjusted relative risk in follow-up studies with stratified incidence-density data. The network approach that Mehta developed for tables with person-count numerators and denominators is adapted to tables with person-count numerators and person-time denominators. This algorithm updates an earlier program by Guess et al, yielding the same quantities but with running times that are between ten and a hundred times faster. Applications to Poisson regression are discussed.

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Feinstein's criticisms of epidemiology are summarized and evaluated. His major premises appear to be that methodologic errors inevitably result in false positive associations, that epidemiologists are complacent about methodology, and that epidemiologists encourage overinterpretation of epidemiologic data by the public. We challenge these premises and discuss a number of technical errors that underlie Feinstein's writings: he generally ignores the tendency of nondifferential exposure misclassification to dilute associations; he inappropriately interchanges measures of disease occurrence, which leads him to erroneous assertions regarding differences among studies; and he asserts that absence of a dose-response gradient precludes causality, despite the fact that causal effects need not follow a monotonic dose-response curve over the entire range of exposure. We also challenge his assertions that contradictory results necessarily indicate poor study methods and that prior beliefs of the data collectors inevitably affect study results in ways not apparent in the study methods. Feinstein's approach to the use of epidemiology in policy formulation ignores the need to weigh all evidence and distinguish important from unimportant biases. We illustrate this point by documenting how the use of Feinstein's “scientific standards” in evaluating the evidence linking aspirin to Reye's syndrome would have led to costly errors in medical practice.

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID