Search PubMed⌕ Search

Biomedical subjects

S Wacholder

Publications and source records attributed to S Wacholder.

122 records · Page 7Linked to original sources
PubMed1986

Selecting subpopulations for intervention.

The effectiveness of a program designed to eliminate exposure to a risk factor may be enhanced by selecting specific subpopulations for the intervention effort. A second factor is called an intervention effect modifier of the first factor if the effect of the intervention. If an intervention effect modifier exists, a program's effectiveness may be enhanced by choosing a subpopulation for intervention on the basis of the distribution of that factor. We discuss the conditions in which intervention effect modification can occur when there is a third factor which influences risk. Additivity of incidence rates, the criterion when only two factors are involved, is neither necessary nor sufficient to rule out intervention effect modification in this situation. We also discuss the cost effectiveness of intervention strategies when the cost per successful intervention varies.

Costs and Cost Analysis↗
PubMed1986

Binomial regression in GLIM: estimating risk ratios and risk differences.

Although an estimate of the odds ratio adjusted for other covariates can be obtained by logistic regression, until now there has been no simple way to estimate other interesting parameters such as the risk ratio and risk difference multivariately for prospective binomial data. These parameters can be estimated in the generalized linear model framework by choosing different link functions or transformations of binomial or binary data. Macros for use with the program GLIM provide a simple method to compute parameters other than the odds ratio while adjusting for confounding factors. A data set presented previously is used as an example.

Biometry↗
PubMed1986

Associations between several sites of cancer and nine organic dusts: results from an hypothesis-generating case-control study in Montreal, 1979-1983.

A multi-cancer site, multi-factor case-control study was undertaken to generate hypotheses about possible occupational carcinogens. Probing interviews were carried out with over 2,000 subjects. All incident cases of 19 sites of cancer in males aged 35-70 and resident in Montreal were eligible. The interview was designed to obtain detailed lifetime job histories, and information on potential confounders. Each job history was reviewed by a team of chemists who translated it into a history of occupational exposures. These occupational exposures were then analyzed as potential risk factors in relation to the sites of cancer included. For each site of cancer analyzed as a case series, controls were selected from among the other cancer sites in the study. This report concerns the associations between sites of cancer for which there were over 100 cases processed (stomach; colorectal, also analyzed by subsites; lung; prostate; bladder; kidney; non-Hodgkin's lymphoma) and nine organic dusts (wood; paper; grain; flour; fabrics; cotton; wool; synthetics; fur). All site-exposure combinations were investigated. The ones that provided the most interesting leads were lung-wood dust (odds ratio (OR) = 1.5), stomach-wood dust (OR = 1.5), colorectal-synthetic fiber (OR = 1.5), bladder-synthetic fiber (OR = 1.8), non-Hodgkin's lymphoma-cotton dust (OR = 1.9), colon-grain dust (OR = 2.6), prostate-grain dust (OR = 2.2), and prostate-paper dust (OR = 2.0). Only the associations with wood dust, synthetic fibers and cotton dust showed some evidence of "dose-response" with duration of exposure. Because it is such a common exposure and appears to increase lung and stomach cancer risks, wood dust may be responsible for a great deal of occupational cancer.

Adult↗
PubMed1985

Familial aggregation and early expression of hyperapobetalipoproteinemia.

Family history is an important predictor of coronary risk. However, this relation, in large part, is not explained by the known risk factors such as systemic hypertension or hyperlipidemia. In the present study, plasma lipid, lipoprotein lipid, and plasma low-density lipoprotein (LDL) apoB levels were measured in 66 offspring (myocardial infarction [MI] offspring) of 24 families in which an index parent had premature coronary artery disease and hyperapobetalipoproteinemia. These results were compared to those obtained in 207 control children and young adults. Univariate analysis revealed that plasma LDL apoB and all other lipid and lipoprotein levels except high-density lipoprotein cholesterol were significantly higher in the MI offspring. Multivariate analysis showed plasma LDL apoB and LDL cholesterol best differentiated the MI offspring from control children and young adults. Of the 66 children, 22 had hyperapobetalipoproteinemia, of whom only 7 had clearly abnormal LDL cholesterol or plasma triglyceride levels. Thus, a substantial portion of children born to a parent with premature coronary artery disease and hyperapobetalipoproteinemia have the same disorder of lipoprotein metabolism.

Adolescent↗
PubMed1985

Conditions for confounding of the risk ratio and of the odds ratio.

There are disagreements in the literature about the criteria to be used to ascertain whether or not a measure of association is confounded. The authors postulate the general principle that a crude unconfounded measure of association is structured as a weighted average of the stratum-specific values of the measure. They examine the relationships between stratum-specific measures of association, crude overall measures, and weighted averages of stratum-specific measures, and indicate how these relationships may be used to define criteria for the assessment of confounding in cohort studies in which the exposure, disease, and stratification variables are classified dichotomously. The criteria presented differ for the risk ratio and for the disease-odds ratio. In other words, one can reach different conclusions about the confounding effect of a given extraneous variable, depending on which measure of association is chosen. This view differs from that of Miettinen and Cook (Confounding: essence and detection. Am J Epidemiol 1981;114:593-603) who postulated one set of criteria for the assessment of confounding, which was applicable to both measures of association. These different approaches may lead to different conclusions about the presence or absence of confounding.

Epidemiology↗
PubMed1984

The relation of risk factors to the development of atherosclerosis in saphenous-vein bypass grafts and the progression of disease in the native circulation. A study 10 years after aortocoronary bypass surgery.

We examined 82 patients 10 years after saphenous-vein aortocoronary bypass surgery to determine their angiographic status and to relate those findings to the risk factors for coronary-artery disease. Of 132 grafts shown to be patent 1 year after surgery, only 50 were unaffected at 10 years. The remainder were narrowed (43) or occluded (39). Disease progression in coronary arteries without grafts was also frequent, both in vessels that were normal (15 of 32) and in those with minor stenosis (25 of 53). New lesions did not develop in 15 patients, whereas they did in 67--in the grafts, the native vessels, or both. There was no significant difference between the two groups in the incidence of hypertension, diabetes, or smoking, whereas plasma levels of very-low-density lipoproteins (VLDLs) and low-density lipoproteins (LDLs) were higher, and high-density lipoprotein (HDL) levels were lower in those with new disease than in those without. Univariate analysis showed that plasma cholesterol and triglyceride levels were significantly higher at the time of surgery and at the 10-year examination in those with new lesions. Multivariate analysis indicated that among the lipoprotein indexes, levels of HDL cholesterol and plasma LDL apoprotein B best distinguished the two groups. The findings indicate that atherosclerosis in these patients was a progressive disease, frequently affecting both the grafts and the native vessels, and that the course of such disease may be related to the plasma lipoprotein levels.

Cholesterol↗
PubMed1982

Association between rates of premature delivery and intra-uterine growth retardation.

It has been suggested that there is a positive epidemiological correlation between the rates of premature delivery and intra-uterine growth retardation. This was tested across three series of live births, cross-classified according to gravidity and mother's age in two states, North Carolina (caucasians and blacks), and Washington (caucasians only) in the years 1970-74 and 1968-77, respectively. Premature-delivery rate was defined as the percentage of all births of known gestational age born before 37 weeks, and a surrogate measure of the growth-retardation rate as the percentage of all births weighing less than 2500g at term (less than or equal to 40 weeks). The correlations between the two rates for caucasian live births in North Carolina and Washington were found to be +0.74 and +0.73 respectively (p less than 0.0005 in each instance). The correlation coefficient (+0.12 for black live births in North Carolina was not significant. The correlation observed among caucasian births suggest that for growth-retarded fetuses, the risk of subsequent premature delivery is abnormally high.

Black or African American↗
PubMed1982

Paired versus two-sample design for a clinical trial of treatments with dichotomous outcome: power considerations.

For the same number of observations in a small-sample clinical trial with dichotomous outcome, the statistical power associated with a two-sample design, analyzed by Fisher's exact test, is slightly greater than that associated with a matched design, analyzed by McNemar's test, and hence of the matched design, is monotone increasing in the within-pair correlation between the treatment responses. Power curves are presented which demonstrate that positive within-pair correlation, even when quite small, can result in a superiority in power for the matched design. Conversely, in the rare situations where there is a negative within-pair correlation, choice of a two-sample design can result in a substantial gain in power.

Clinical Trials as Topic↗
PubMed1977

Insulin, obesity, and triglyceride interrelationships in sixteen children with familial hypertriglyceridemia.

Sixteen children with familial hypertriglyceridemia were studied to determine whether there were any distinctive insulintriglycerid-obesity relationships in pediatric familial hypertriglyceridemia. Eleven of 16 children had calculated fat mass greater than the 97th percentile for age, height, and sex. When compared with 16 normal control subjects matched for degree of obesity immunoreactive insulin and glucose response during oral glucose tolerance was similar for normal and hypertriglyceridemic children. By either simple correlation or multiple regression analysis, plasma, triglycerides did not correlate significantly with measurements of insulin or obesity in hypertriglyceridemic or normal children. Within the limits of a small sample size, and in the presence of obesity, insulin does not appear to play a predominant role in the genesis of hypertriglyceridemia in children with familial hypertriglyceridemia. With a small mean weight loss of 1.8 kg and adherence to a diet with 20% of calories as protein, 40% each as fat and carbohydrate, polyunsaturate to saturate ratio of 1.5:1, mean plasma triglycerides were reduced from 238 to 140 mg/100 ml in the 11 obese children with familial hypertriglyceridemia (P less than 0.02). Speculation In spite of the complicating role of obesity, adolescence, and the small sample size, it is interesting to note that the correlation coefficients between triglyceride and insulin/glucose area (0.36), and insulin area (0.30), although not significant (P less than 0.1), were considerably higher in hypertriglyceridemic children than in normal subjects in whom comparable correlation coefficients were 0.08 and 0.08. This infers that the potential role of insulin in triglyceride metabolism in children with familial hypertriglyceridemia might be discerned with longitudinal follow-up into adulthood.

Adolescent↗
PubMedDate not supplied

The partial questionnaire design for case-control studies.

We propose an alternative to a long questionnaire that may increase quality while reducing the cost and effort of participants and researchers. In the 'partial questionnaire design', information about the exposure of interest is obtained from all subjects, while zero, one, or more disjoint subsets of questions about possible confounders are asked to randomly selected subgroups. The proposed analyses exploit the fact that the uncollected data can be considered to be missing at random. We show that it is possible to obtain high efficiency for estimating the effect of exposure of interest, adjusted for confounding, while substantially shortening average questionnaire length.

Bias↗
PubMedDate not supplied

A comparison of three approaches to estimate exposure-specific incidence rates from population-based case-control data.

In population-based case-control studies, an attempt is made to identify all incident cases diagnosed in a specified population during a fixed time interval. Assuming that this goal is met allows one to obtain measures of risk other than relative risks. In this paper, we describe three approaches to estimate exposure-specific incidence rates. Approach 1 relies on estimating crude incidence rates of the disease in strata defined, for instance, by age and geographic area, and combining them with relative risk estimates from the case-control data. In approaches 2 and 3, baseline incidence rates and relative risks are estimated jointly. Approach 2 is based on a pseudo-likelihood, while, in approach 3, the problem is regarded as a missing data problem and a full likelihood is maximized. We applied these three approaches to a study of bladder cancer. Our three sets of estimates of exposure-specific incidence rates were in close agreement, while there appeared to be greater precision with approaches 2 and 3.

Adult↗
PubMedDate not supplied

Is cigarette smoking a risk factor for non-Hodgkin's lymphoma or multiple myeloma? Results from the Lutheran Brotherhood Cohort Study.

Among 17,633 U.S. white male insurance policy holders whose use of tobacco was characterized in a 1966 self-administered questionnaire, there were 49 deaths from non-Hodgkin's lymphoma (NHL) and 21 from multiple myeloma (MM) during a 20-year follow-up. Men who had ever smoked cigarettes had an elevated mortality from NHL (RR = 2.1; CI = 0.9-4.9), with risk almost four-fold greater among the heaviest smokers (RR = 3.8; CI = 1.4-10.1) compared with those who used no tobacco. In contrast, risk of MM was only slightly elevated among those who had ever smoked cigarettes (RR = 1.3; CI = 0.4-3.9) and without evidence of a dose-response trend. Since this is the first cohort study suggesting a link between cigarette smoking and NHL and findings from case-control studies have been inconsistent, additional clarification should be sought from larger incidence-based cohort investigations.

Adult↗
PubMedDate not supplied

Hyperapobetalipoproteinemia. Plasma lipoprotein responses to oral fat load.

To better define lipid transport in patients with hyperapobetalipoproteinemia (HyperapoB), the response to an oral fat load was studied in six normotriglyceridemic patients with the disorder. Plasma triglycerides; Sf greater than 400, and Sf 20 to 400 triglycerides; Sf greater than 20 B100; total HDL and HDL subfractions (HDL2 and HDL3) were measured serially for a 7-hour period after an oral fat load and changes in these parameters were compared to those observed in six normolipidemic controls. In addition, plasma triglyceride levels and HDL2 and HDL3 cholesterol were also determined in seven patients with Type IV hyperlipoproteinemia: three with normal LDL apo B levels and four with HyperapoB. When the two normotriglyceridemic groups were compared, the patients with HyperapoB had significantly higher fasting levels of SF greater than 400 lipoproteins and higher fasting VLDL and LDL levels than the normal patients. After the fat load, Sf 20 to 400 triglycerides and Sf greater than 20 B100 levels increased in both groups. Plasma triglycerides rose to a higher level in the HyperapoB patients than in the normal group, but more strikingly, remained elevated in the HyperapoB patients, an elevation due principally to a persistant increase in Sf greater than 400 triglycerides. On the other hand, HDL2 cholesterol dropped substantially in the HyperapoB patients but not in the normal patients. Finally, in the hypertriglyceridemic group, after the fat load, HDL2 cholesterol levels did not change in the patients with normal LDL apo B levels but did decrease in those with elevated plasma LDL apo B.

Adult↗