Journal of chronic diseases最新文献

Physicians use the concept of stability to estimate the likelihood that a patient will deteriorate during a hospitalization. To determine whether physicians can accurately predict a patient's risk of morbidity, 603 patients admitted to the medical service during a one month period were rated prospectively as to how stable they were.

Overall, 15% of patients had deterioration of already compromised systems, while 17% had new complications, such as sepsis. Eight percent of patients had both. Twelve percent of stable patients experienced morbidity; 39% of the somewhat unstable and 61% of the most unstable. When all of the demographic and clinical variables were taken into account including the reason for admission and comorbid diseases, the residents' estimates of the patient's stability was the most significant predictor of morbidity (p < 0.001).

The judgment that a patient was stable had an 87% negative predictive accuracy, while the judgment unstable had a 46% positive predictive accuracy.

The forced expiratory volume in one second (FEV₁) is routinely used in epidemiologic studies of lung function to assess the presence and severity of obstructive airways disease. Normative prediction equations developed using data from healthy, asymptomatic individuals may then be used both in a clinical setting and to adjust comparisons among risk subgroups for known demographic differences. Unfortunately no concensus has yet developed as to how best to model lung function data. This paper addresses this issue in a systematic manner using data derived from two cohorts followed over a period of 9–11 years. We compare a variety of cross-sectional and longitudinal models for FEV₁, show how they may be expressed as members of a larger class of general linear models, and discuss goodness-of-fit procedures for comparing them. We found little objective evidence for discriminating among these models; only those fit to FEV₁/ht³ performed poorly. We argue on subjective grounds for the use of models based on FEV₁, as a function of age, height and their interactions.

This paper reviews the sources of apparent time trends in effect. Apparent changes in effect may arise from changes in covariate distributions, background rates, exposure distribution, measurement quality, or selection factors. As with time trends in rates, time trends in effect must have at least one of these sources, since time itself has no effect. If background incidence is changing, however, time trends in effect become dependent on choice of effect measure, and interpretation must take this into account. Evidence that a trend arises from age-, cohort-, or period-related phenomena can indicate the relative plausibility of different explanations of the trend. Conversely, the relative plausibility of each explanation may indicate whether the trend is most appropriately viewed over the axis of age, birth cohort, or calendar time. Nevertheless, studies of short duration relative to an apparent trend (such as most case-control studies) must invoke strong assumptions to justify focusing on a particular axis. Illustrations are given from studies of electronic fetal monitoring and of smoking and lung cancer.

This paper uses a detailed example to illustrate how to detect individual observations that disproportionately influence the results of hypothesis testing with relative risk regression models.

Consistency and plausibility are fundamental criteria for judging cause and effect from observational studies. They are applied here to the interpretation of data from a population-based case-control study of oral contraceptives and breast cancer. A preliminary analysis of oral contraceptive use in young nulliparous women, who had no family history of either breast cancer or benign breast disease, showed a statistically significant dose-response, with long-term users (49 months or more) having an apparent 4-fold elevation in risk of early breast cancer. Further analyses, however, revealed striking inconsistencies which were biologically implausible. These effectively undermine cause and effect as an explanation for the initial finding.

Blood pressures (BP) were determined in 1409 boys aged 8–16 years at three one-year intervals in New York City (NYC) and in Greece, areas of high and low incidence of coronary heart disease (CHD), respectively. Non-Greek American boys had significantly lower systolic and diastolic BP than all the Greek boys from NYC and from Greece. The boys residing in Crete and in Athens had higher BP than all other cohorts. After covariance adjustment for height, ponderal index and age, significant differences among the cohorts showed the non-Greek American cohort to have the lowest and the Cretan cohorts the highest BP levels. The Cretans lead a lifestyle noted for the absence of other risk factors for CHD. Thus, while the incremental increase in blood pressure might have a corresponding increase in CHD risk among individuals, there are fewer individuals in Crete at elevated risk overall based on the CHD experience of the U.S. and Greece.