Journal of chronic diseases最新文献

Case-control studies of screening efficacy have been proposed as a cost- and timeefficient alternative to randomized controlled trials. Possible source populations for such retrospective studies of breast cancer screening are considered, including women from (i) pre-existing randomized trials, (ii) non-experimental population-based studies and (iii) detection centers. On practical grounds women attending detection centers are seen to comprise the most readily accessible source of adequate numbers of cases and controls. Potential biases are addressed, involving incomplete case ascertainment, self-selection, and different screening recommendations. Data from the Guttman Breast Diagnostic Institute are used for illustration.

Data from a case-control study of breast cancer in 441 cases and matched controls aged ≤38 in Los Angeles is fitted to two models of carcinogenesis: the two-stage model of Moolgavkar and Knudson; and a multistage adaptation of the log/log model proposed by Pike et al.

In the two-stage model, risk factors (here age at menarche, age at first pregnancy, abortion, regularity of cycling, benign breast disease, and use of oral contraceptives (OCs)) are postulated to act either by increasing the rate of mutation of normal to intermediate or of intermediate to malignant stage cells, or by increasing the proliferation rates of such cells. In the multistage model, it is postulated that all transition rates are equally determined by the rate of cell turnover, which is in turn influenced by risk factors. In both models, positive family history is modelled in two ways; (1) all cells may have started in an intermediate stage at birth, with probability depending on the number and degree of affected family members; or (2) as an event rate modifier in the same way as other covariates.

With only menarche or menarche and family history included, the multistage and two-stage models both produced likelihoods very similar to those from a simple logistic model, though both fit better than the logistic model as more covariates were added to the model. The two stage models offer greater flexibility in modelling the time at which each factor is most effective, We found irregular menstrual cycling to reduce the rate of proliferation of normal cells or their mutation rate to intermediate cells by 50% (p < 0.025) and use of OCs to increase these rates by 3.25 fold (p < 0.01). Having completed a pregnancy of more than 26 weeks gestation appeared to reduce the rate of intermediate cell proliferation by 5% (p < 0.05) relative to a baseline rate of 14% per year. Benign breast disease was associated with a 1.60 fold increased rate of the second mutation (p < 0.025). In all models, family history was by far the strongest risk factor (RR = 4.44 from the logistic model, p < 0.0001). Covariates showed similar effects in the multistage model, though their magnitudes were slightly different.

A recently published randomized, controlled, double-blind, study has reported efficacy of zinc gluconate lozenge treatment of the common cold. Because of a higher rate of side effects in the zinc group and the lack of any confirmatory evidence of blinding efficacy, we are concerned about the possible contribution of bias to the study result. Unflavored zinc gluconate tablets can be easily distinguished from the relatively tasteless, unflavored calcium lactate tablets, which were used as placebo in the cited study, increasing our concern about bias.

In order to be able to test zinc lozenges in a second trial of common cold therapy, we developed a matching placebo containing denatonium benzoate (a bitter substance used to prevent thumb sucking in children) and then undertook a formal evaluation of blinding efficacy. This article reports the results of this evaluation, encompassing two randomized, controlled taste trials; the first trial of the placebo matching showed zinc recipients to exhibit a higher rate of side effects and also a significantly higher proportion of subjects believing they were on “active” treatment. Alterations in dosage before the second taste trial yielded comparability of the placebo and zinc lozenges.

This study illustrates the pitfalls which may sometimes be encountered in performing and publishing studies in which placebos are either (a) not tested at all or (b) tested in too small a subject population to detect a significant subjective difference between the placebo and the active medication.

The objective of this study was to develop a prospectively applicable method for classifying comorbid conditions which might alter the risk of mortality for use in longitudinal studies. A weighted index that takes into account the number and the seriousness of comorbid disease was developed in a cohort of 559 medical patients. The 1-yr mortality rates for the different scores were: “0”, 12% (181); “1–2”, 26% (225); “3–4”, 52% (71); and “⩾ 5”, 85% (82). The index was tested for its ability to predict risk of death from comorbid disease in the second cohort of 685 patients during a 10-yr follow-up. The percent of patients who died of comorbid disease for the different scores were: “0”, 8% (588); “1”, 25% (54); “2”, 48% (25); “ ⩾ 3”, 59% (18). With each increased level of the comorbidity index, there were stepwise increases in the cumulative mortality attributable to comorbid disease (log rank χ² = 165; p < 0.0001). In this longer follow-up, age was also a predictor of mortality (p < 0.001). The new index performed similarly to a previous system devised by Kaplan and Feinstein. The method of classifying comorbidity provides a simple, readily applicable and valid method of estimating risk of death from comorbid disease for use in longitudinal studies. Further work in larger populations is still required to refine the approach because the number of patients with any given condition in this study was relatively small.

The Framingham Heart Study has been the foundation upon which several national policies regarding risk factors for coronary heart disease mortality are based. The NHANES I Epidemiologic Followup Study is the first national cohort study based upon a comprehensive medical examination of a probability sample of United States adults. The average follow-up time was 10 years. This study afforded an opportunity to evaluate the generalizability of the Framingham risk model, using systolic blood pressure, total cholesterol, and cigarette smoking, to the U.S. population with respect to predicting death from coronary heart disease. The Framingham model predicts remarkably well for this national sample. The major risk factors for coronary heart disease mortality described in previous Framingham analyses are applicable to the United States white adult population.

We examined the correlates of the Quality of Life Index (QLI) in three samples of cancer patients: newly diagnosed (N = 397), recipients of chemotherapy (N = 194), and terminal (N = 2046). The relative importance of physical, emotional, social, and disease symptom characteristics in predicting the QLI was compared across samples. Despite differences in data collection approaches (telephone, personal interview, or paper and pencil) and differences in patient characteristics, the QLI was a robust construct with its central organizing principle being physical functioning. In all samples, functioning, symptoms, depression, and social support were significant predictors of the QLI, while age and cancer type were only minimally related. The QLI significantly differentiated between patients at different disease phases and measured more than physiological functioning. However analyses suggested that the dominant factor constraining the range of human psychosocial functioning was physical condition.

To develop guidelines for evaluation of case-control reports a survey of 37 experts in the performance and evaluation of case-control studies was conducted. A majority of the respondents listed 20 items as essential; 80–90% considered identification of case and control sources, exclusion criteria, and response rate as essential; 75–80% considered information on methods of data collection, “blinding” of interviewers, investigation of bias, and methods of dealing with confounding variables essential; 70% considered a description of the analytic methods and 57% the presentation of confidence limits essential.

Twenty items judged essential by more than half the survey participants were used as guidelines to appraise 48 case-control studies published in 1984. In 88% of these studies information was lacking on at least one of the items. The proposed guidelines serve as a framework for readers to effectively assess the validity of a case-control report.

This paper proposes that a broader health assessment be made in the Framingham Offspring/Spouse Study than is undertaken in the Framingham Study. The Offspring Study is composed of the children (and their spouses) of the members of the original Framingham Study cohort. The Offspring population has a broader age range and an average agc that is approximately 30 years younger than the original parent cohort. Therefore, mortality and morbidity measures, which were used as indices of health status for the parent cohort and which focus on the negative “sickness” component of health, are less appropriate for use in this relatively healthy population. Thus, we propose a broader conceptual framework of health that emphasizes the positive “wellness” side of the health continuum. The essential components of the comprehensive health index we describe include global health perceptions, measures of physical, mental, and social functioning across valued social roles, the ability to withstand stress as mediated by the coping process and social resources, and the assessment of genetic, behavioral, and physiological risk factors. One purpose of the proposal is to stimulate discussion in the hope of achieving general agreement regarding a shared conceptual frame of reference that would guide the development and testing of a reliable and valid health status instrument.