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

摘要:

The relation between cervical cancer and dietary intake of vitamins A, C, and E, beta-carotene, and selenium was examined in a population-based case-control study in Utah. Cervical cancer cases (n = 266) and population-based controls (n = 408) were interviewed between 1984 and 1987. Protective effects were observed for vitamins A, C, and E and beta-carotene but were attenuated by age, level of education, and lifetime cigarette use. Associated risk (comparing highest with lowest quartiles of intake) went from 0.53 (crude) to 0.71 (adjusted) for vitamin A; from 0.55 (crude) to 0.82 (adjusted) for beta-carotene; from 0.45 (crude) to 0.55 (adjusted) for vitamin C; from 0.58 (crude) to 0.60 (adjusted) for vitamin E; and from 0.95 (crude) to 0.70 (adjusted) for selenium. Adjustment for number of sex partners and church attendance, factors significantly related to cervical cancer risk, only slightly attenuated these adjusted risk estimates.

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Birth-weight-specific mortality is lower for black prematures than white prematures of similar low birth weight. The reason for this well-recognized phenomenon is unknown. We investigated the extent to which black and white infants differ in their gestational maturity and incidence of potentially lethal risk factors, and the effect these factors might have on differential mortality risk. The population studied comprised babies bom alive in a tertiary care hospital with birth weights from 700 to 1800 g over a 41/2-year period. Univariate analysis showed no important difference between races for the incidence of lung disease, Apgar scores, birth weight, or gestational age. Infants with a birth weight below the 10th percentile (small for gestational age) were more likely to be black, and infants with a birth weight above the 90th percentile (large for gestational age) who had a survival disadvantage were usually white. The crude odds ratio for the white race was 1.79 (1.18–2.73). When the demographic, morbidity, and growth variables were put into a logistic model, the odds ratio changed only slightly, to 1.52 (1. 14–2.03). We conclude that the majority of the black-white difference in birth-weight-specific survival is not due to a higher incidence of black small-for-gestational-age infants, nor is it due to differences in major morbidities associated with death.

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Most versions of the multistage model predict that when persons stop smoking, their excess risk for lung cancer will continue to increase. Discussions of the model usually indicate that the excess risk stabilizes. The data show that the risk declines. Implications for models of carcinogenesis are discussed.

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Several recent publications have used, without demonstrating its derivation, a mathematical model that describes the risk of being infected by a sexually transmitted agent as a function of four parameters: the number of partners, the number of contacts with each partner, the per-contact probability of transmission, and the probability of a partner being infected. The model is derived both from elementary probability concepts and, more formally, by using the binomial expansion and conditional probabilities. The assumptions involved in these derivations are brought out, as are the limitations they impose on the uses of the model. The model equations used so far in published studies are shown to be special cases of a general form that allows for more variability of the sexual behavior modeled. The different uses to which the model has been put are categorized, and some further ones are suggested.

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The case-exposure study, described in 1983, is a modification of the case-control study that allows estimation of risk ratios without need for a rare-disease assumption. For a fixed population the approach is the same as the case-base or case-cohort study. Two sampling strategies have been described for extending application of the case-exposure approach to stationary populations, although the validity of the extension was not proven. As shown here, the two sampling strategies for stationary populations can provide valid estimates of the risk ratio, but restrictive assumptions related to stationarity may limit application of the strategy. We also show that the case-exposure study depends on the stationarity assumptions in a different, possibly more restrictive way than some other case-control approaches. We emphasize limitations of the case-exposure study that may preclude its use, particularly it the period of risk is long.

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Graphics displaying all confidence intervals around a point estimate have been referred to as P-value functions and consonance intervals. We recommend use of the term confidence interval function (CI function) rather than P-value function. The CI function is useful because it simultaneously depicts point estimation, variability, and the relation of these two factors to the null value. The usefulness of the CI function in demonstrating the concepts of effect modification and confounding, in meta-analysis, and in the comparison of various confidence interval procedures is evaluated. Software packages that produce CI functions are described.

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Adjustments for making multiple comparisons in large bodies of data are recommended to avoid rejecting the null hypothesis too readily. Unfortunately, reducing the type I error for null associations increases the type II error for those associations that are not null. The theoretical basis for advocating a routine adjustment for multiple comparisons is the “universal null hypothesis” that “chance” serves as the first-order explanation for observed phenomena. This hypothesis undermines the basic premises of empirical research, which holds that nature hollows regular laws that may he studied through observations. A policy of not making adjustments for multiple comparisons is preferable because it will lead to fewer errors of interpretation when the data under evaluation are not random numbers but actual observations on nature. Furthermore, scientists should not he so reluctant to explore leads that may turn out to he wrong that they penalize themselves by missing possibly important findings.

ISSN:1044-3983    

出版商:OVID    

年代:1990

数据来源: OVID