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The development and validation of a caries prediction model comprising 13 sociodemographic and dental examination variables on Grade 1 and Grade 5 children in the National Preventive Dentistry Demonstration Program are described. The objective was to derive a method of predicting children at high risk to caries early in order that preventive measures might be undertaken. True high risk children were defined in two ways: highest 25% of children based on their 4-yr DMFS increment, and their total DMFS score at the end of the study. In both cases, children predicted to be at high risk were defined as the 25% with the highest discriminant score. Discriminant function and logistic regression analyses were used to determine the extent to which the 13 variables collectively discriminated between true high risk and non-high risk children so defined. Sensitivity was approximately 0.50 and specificity around 0.82, using the 4-yr increment as the criterion for defining true high risk, and approximately 0.64 and 0.88, respectively, using the final DMFS score for defining true high risk.

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Probabilities of caries risk over time measured from eruption of first and second molars are illustrated using life table methodology. Life table rates based on 4,365 children in the National Preventive Dentistry Demonstration Program indicate that both fluoridation and sealants are effective in preventing caries on occlusal and buccal/lingual surfaces of molars. Effectiveness would probably have been greater on occlusal surfaces if sealants had been applied closer to the time of eruption. Similarities and differences between conventional DMFS indices and life table probabilities are discussed.

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Descriptive and statistical age-period-cohort (APC) analysis methods have received considerable attention in the literature. The statistical modeling of APC data often involves the popular multiple classification model, a model containing the effects of age groups (rows), periods of observation (columns), and birth cohorts (diagonals of the age-by-period table). The identifiability problem inherent to this model is discussed, and its adverse effects on the results of APC modeling exercises are illustrated numerically. Potential problems attendant with the use of two-factor models are described, and other possible modeling approaches currently in use are discussed. Interpretational limitations due to certain innate characteristics of typical APC data sets are also detailed. Given all the documented potential sources for error, the current state-of-the-art regarding the statistical modeling of APC data should be considered to be at an early stage of development.

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Analysis of statistical methods used in matched case-control studies of toxic shock syndrome shows that matching has implications for validity and precision of the studies and for the choice of analysis techniques. The studies considered accounted for the matching in the analysis, either by the Mantel-Haenszel or Miettinen-Pike-Morrow approach to 1-to-M matched designs, or by the use of conditional maximum likelihood fitting of logistic regression models. Methods of dealing with confounding and effect modification in the (matched) logistic regression model are presented in the context of studies of toxic shock syndrome. The varied statistical techniques used in these studies were generally appropriate to the matched design except that nonmatching variables were not thoroughly considered as effect modifiers or confounders.

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Seventy-nine patients with endometrial carcinoma were compared with 203 control subjects regarding their use of combination-product oral contraceptives (OCs). Overall, 6.3% of patients and 15.3% of control subjects had used these products. The risk of endometrial cancer for users of OCs was less than half the risk for nonusers. Five years or more of use reduced the risk to a third. Recent users were strongly protected, whereas discontinuation resulted in risks returning to those of nonusers. Furthermore, OCs with predominantly progestational effects of intermediate formulations produced greater protection than those with predominantly estrogens. This pattern of results is biologically consistent with a protective effect of combination-product OCs against endometrial carcinoma.

PIP: 79 patients with endometrial carcinoma were compared with 203 control subjects regarding their use of combined oral contraceptives (OCs). The patients comprised all North Carolina residents with histologically confirmed endometrial carcinoma initially treated at North Carolina Memorial Hospital between 1970-76. Overall, 6.3% of patients and 15.3% of control subjects had used these products. The risk of endometrail cancer for users of OCs was less than half the risk for nonusers. 5 years or more of use reduced the risk to a third. Recent users were strongly protected, whereas discontinuation resulted in risks returning to those of nonusers. Furthermore, OCs with predominantly progestational effects or intermediate formulations produced greater protection than those predominantly estrogenic. This pattern is biologically consistent with a protective effect of combined OCs against endometrial carcinoma.

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Clinical stage and pathological characteristics of endometrial cancer cases were related to several aspects of estrogen prescribing. In comparing 256 cases with 321 community control subjects, estrogen use of less than 3 1/2 years' duration did not increase the risk of endometrial cancer for any stage, grade, histological type, or extent of ivasion. With long-term estrogen use (3 1/2 years or more), relative risks were significantly increased (5.2 to 7.6) for the early cancers--those clinically stage IA, histologically grade 1, and invading the endometrium only. These increases were seen with both high-dose (greater than 0.625 mg) and low-dose (less than or equal to 0.625 mg) preparations. Risks were only minimally increased for the more advanced cancers. However, long-duration estrogen use did produce an increased risk of advanced cancer when administration was continuous rather than cyclic.

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To address the issue of detection bias among endometrial cancer cases and controls, women admitted to the North Carolina Memorial Hospital for dilatation and curettage (D&C) during 1970-1976 were selected as one of three control groups in a study of endometrial cancer and exogenous estrogen. Study subjects included 256 cases, 316 D&C controls, 224 gynecology controls and 321 community controls. The D&C controls had a higher frequency of estrogen use than either of the other control groups or the cases. These differences existed for both blacks and whites. When white cases were compared to either gynecology or community controls, relative risks were increased for long duration estrogen use and for recent use prior to diagnosis. With D&C controls, relative risks were not significantly different from unity irrespective of duration or recency of estrogen use. Exclusion of hyperplasias from the D&C controls had no substantive effect of these results. Bleeding was a presenting complaint for 92% of cases, 82% of D&C controls and 22% of gynecology controls. Both among cases and gynecology controls, there was no statistically significant association between bleeding and estrogen use, whereas this association was evident among D&C controls, and specifically among those who did not have pathologic evidence of endometrial hyperplasia. These data support the presence of detection bias among D&C controls but they do not provide evidence of this bias among endometrial cancer cases.

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PIP: The relationship between exogenous estrogen and risk of endometrial carcinoma was investigated in 256 women with pathologically confirmed cases, 224 gynecology controls, and 321 community controls. Sources of data included personal interviews, physicians' records, and hospital records; diagnoses were verified by 2 outside pathologists. Black women revealed no difference in estrogen use between the cases and both sets of controls, while white women revealed risk of 3.6 and 4.1 after 3 1/2 years of estrogen use. Shorter duration of use, irrespective of dose or type of estrogen, did not increase risk. There was no increased risk in obese women, who prosumably produce increased amounts of exogenous estrogen. The highest risk was found after 3 1/2 years or more of use in nonobese, nonhypertensive women. It was also demonstrated that there is a latency period of 3-6 years after first administration, and that an estrogen-free interval of 2 years is sufficient to reduce elevated risks to nonuser level. Risks of cancer were high for Stage 1A and Grade 1 lesions with estrogen use of long duration.^ieng

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PIP: Methodologic issues inherent in epidemiologic studies of an infrequent cancer that is putatively associated with medication of high-use prevalence are reviewed, using as example effects of endometrial cancer study designs and data interpretation which are caused by changing patterns of estrogen use or hysterectomy. Problems common to all types of epidemiologic studies include pathologic classification, data collection, indications for the therapy vs. the therapy as cause, and patient use of medical care. Specifically, problems with studying the association of endometrial cancer and estrogen use include incorrect carcinoma vs. hyperplasia diagnosis, accuracy of estrogen use information (pharmacy files are recommended), patient compliance, duration of data collection (10 years is best compromise from the ideal of a lifetime history), and type of data collected (natural vs. synthetic estrogen, progesterone content, duration of use, dosage, continuous or interrupted schedule, route of administration). Proper design of follow-up, cohort, and case-compeer studies is outlined. Cohort and follow-up studies have the major advantage of following several outcomes simultaneously. The importance of risk-benefit evaluations (e.g., value of estrogen usage for specific indications) is emphasized.^ieng

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Reports in the lay press that exogenous estrogens cause endometrial cancer are unjustified with the present evidence. The epidemiologic method used to identify retrospectively an increased association of estrogens with endometrial cancer cannot prove causality. Mortality from endometrial carcinoma has not increased in this country and may actually be starting to decline.

PIP: Reports in the lay press that exogenous estrogens cause endometrial cancer are unjustified with the present evidence. Mortality from endometrial cancer has not increased in the U.S. in recent years. Endometrial cancer accounts for only 1.38% of all female cancer deaths. The incidence in the U.S. has not increased since estrogen therapy has been more widely used. The acquisition of an unbiased control group is the prime requirement if valid conclusions are to be made. 1 of the most difficult problems in a retrospective study of endometrial cancer is identification of a group of women who have undergone diagnostic uterine curettage or biopsy or hysterectomy. Exclusion from the comparison group of women who have had a hysterectomy excludes a large number who would have had an opportunity for estrogen replacement therapy following the menopause. An association between 2 factors does not prove cause. It is to be hoped that fear of endometrial cancer from exogenous estrogen therapy will turn out to be a false alarm when better retrospective studies are reported or when material from the studies reported to date is reviewed further. Meantime caution is indicated. Cyclic administration of estrogens in small doses for the shortest practical time is advised. Periodic examinations, Papanicolaou smears, and frequent evaluation of the patient's symptoms are recommended. There are definite and established benefits of estrogen therapy as well as risks.

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