SEARCH · PubMed Health

Results for “Logistic Models”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources

PubMed1978

[Determining the average posteruptive age of teeth from the results of cross-sectional studies (author's transl)].

If results of cross-sectional studies must be used as a basis for setting up models of development of caries in permanent teeth, then the average rather than individual posteruptive age of teeth has to be resorted to. Data available for this purpose had been obtained from a total of 54,000 children living in two G.D.R. cities, namely, Plauen and Karl-Marx-Stadt, as well as from two surveys made in 1959 and 1971, respectively. Calculation of the average posteruptive age of teeth assumes good knowledge of the distribution of dates of eruption in a population. Of the three types of distribution considered, namely, normal, lognormal, and log-logistic distribution, the log-logistic model proved to be superior to others because of better adaptation to the data available. The method of calculating the posteruptive age of teeth is described and illustrated by use of a number of examples. Since one of the two surveys (namely that which was made in Karl-Marx-Stadt in 1971) was made after twelve years' drinking water fluoridation, it was possible to study the effect of fluoridation upon the eruptive behavior of permanent teeth. The results of this study confirmed those obtained during previous investigations.

Adolescent↗

PubMed1977

Time delays in single species growth models.

A general model is considered for the growth of a single species population which describes the per unit growth rate as a general functional of past population sizes. Solutions near equilibrium are studied as function of epsilon = 1/b, the reciprocal of the inherent per unit growth rate b of the population in the absense of any density constraints. Roughly speaking, it is shown that for large epsilon the equilibrium is asymptotically stable and that for epsilon small the solutions show divergent oscillations around the equilibrium. In the latter case a first order approximation is obtained by means of singular perturbation methods. The results are illustrated by means of a numerically integrated delay-logistic model.

Models, Theoretical↗

PubMed1979

Prognostic factors affecting remission, remission duration, and survival in adult acute nonlymphocytic leukemia.

The medical records of 94 consecutive patients with acute nonlymphocytic leukemia (ANLL) were reviewed to identify significant prognostic factors. The data were analyzed using 1) Cox's linear hazard and linear logistic models, 2) chi-square comparison of the groups living longer than 2 years and those living less than 2 years, and 3) the Gehan-Breslow test of equal survival curves. The only statistically significant finding was that the presence of promyelocytic cell type and complete remission correlated with increased survival (p less than .05), but this was negated by the small number of patients with this cell type. There was a suggestive association between higher initial hemoglobin and survival (p = .09). The Gehan-Breslow test revealed a possible difference in survival between those patients more than 51 years of age and those less than 51 (p = .10). Thus none of the commonly accepted prognostic factors in acute nonlymphocytic leukemia was definitely shown to be useful. The findings of this study support an aggressive approach toward all patients with this disease.

Adolescent↗

PubMed1992

Adenoma--carcinoma sequence or "de novo" carcinogenesis? A study of adenomatous remnants in a population-based series of large bowel cancers.

Although it is well known that colorectal cancers can arise on a preexisting adenoma or de novo, the relative importance of these two pathways is still highly controversial. The authors studied the proportion of cancers with adenomatous remnants in a nonselected population-based series of 1630 resected colorectal cancers, so that they could estimate by subsite the importance of the adenoma-carcinoma sequence. Four factors appeared to be related independently to the presence of adenomatous tissue within cancers in a multiple logistic model: tumor extension, growth pattern, location, and size. It appeared that infiltrating and ulcero-infiltrating tumors, which represented 39.8% of all resected colorectal cancers, very rarely displayed adenomatous tissue (0.5%), whereas it was more common in fungating and ulcero-fungating cancers (25.8%; P less than 0.001). In these exophytic cancers, the presence of adenomatous tissue was related very closely to the tumor size and extension, and it was seen in as many as 83% of small cancers (less than 2 cm) limited to the mucosa or submucosa. Right colon cancer showed consistently fewer adenomatous remnants than left colon or rectal cancer. These figures suggest that there are roughly two types of colorectal cancers, one of the infiltrating or ulcero-infiltrating type, which usually would arise de novo and account for approximately 40% of all colorectal cancer cases, and the exophytic type, which would mainly follow an adenoma-carcinoma sequence, although some might be de novo cancers, in particular in the right colon.

Adenocarcinoma↗

PubMed1992

Non-fatal farm injuries on 117 eastern Ontario beef and dairy farms: a one-year study.

A one-year prospective survey was conducted to study the incidence of and potential risk factors for farm-related injuries in Eastern Ontario. One hundred and seventeen dairy and beef farms were surveyed using a personal interview. Information was collected on demographic characteristics of the farm owners, workers, and families; characteristics of the farm operations; and information on behaviors potentially affecting injury risk. Monthly telephone contact was then maintained with the farms for one year in order to document all farm-related injuries. Overall and specific injury rates were calculated. Treatment patterns for these injuries were described. The statistical significance of several potential risk factors for injury was evaluated; assessment of relative risk estimates (RR) and adjustment for confounding factors was done using logistic regression analysis. The overall farm injury rate was 7.0 persons injured per 100 person-years (95% C.I.: 4.9,9.1, n = 547). Common patterns of injury by ICD-9-E-Code included accidents caused by farm machinery (E919.0), accidental falls (E880-8), and injuries caused by animals (E906). Variables found in multivariate logistic models to be predictive of injury occurrence were living on a beef farm (RR = 2.5; p = 0.01); increased farm work experience (trend: p less than 0.01); full-time exposure to farm work (RR = 2.5; p = 0.04); and, in farm owners, the use of prescriptions medications (RR = 2.7; p = 0.07). Forty-six percent of the farm-related injuries were treated in a hospital-based emergency department (ER). Efforts to monitor the incidence of farm injuries using an ER-based information system have the potential to significantly under-estimate the scope of the regional farm injury problem in Eastern Ontario.

Accidents, Occupational↗

PubMed1992

Genetic-epidemiologic study of omphalocele and gastroschisis: evidence for heterogeneity.

On the basis of clinical manifestations, epidemiologic characteristics, and the presence of additional malformations, omphalocele (OM) and gastroschisis (GA) are considered casually and pathogenetically distinct abdominal wall defects. More than 50% of infants with OM have additional defects, but only about 15% of those with GA do. To evaluate whether there is heterogeneity between isolated and multiply affected cases of OM and GA, we analyzed epidemiologic characteristics and familial risks of major defects for 82 OM and 81 GA cases drawn from a population-based study in the Maryland-Washington, DC-Northern Virginia area and born from 1980 through June 1987. We examined year of birth, sex, race, and maternal age distributions after stratifying the infants into isolated and multiple defect groups. We found significant differences in maternal age between cases with isolated OM and GA, but not between cases with GA or OM who had other defects. Using regressive logistic models, we analyzed familial aggregation of birth defects among relatives of infants with OM and GA. An autosomal recessive model of inheritance was found to be the most parsimonious explanation for the families of infants with isolated OM or GA. However, for families of infants with multiple defects, a sporadic or nongenetic model fit best. These findings are not only useful for estimating familial risk of major birth defects, but they also suggest further heterogeneity of infants with OM and GA according to the presence of other malformations.

Abdominal Muscles↗

PubMed1992

Statistical review of the henhouse experiments: the effects of a pulsed magnetic field on chick embryos.

This paper analyzes data from a study conducted by the United States Office of Naval Research on the effects of pulsed magnetic fields on chick embryos. The experiment involved incubation of eggs under carefully controlled conditions in six different laboratories. The original analysis included inappropriate statistical methodology for analyzing the experimental results. Since the conclusions from this study rest so heavily on the results of statistical analyses, choosing the proper methodology is imperative. The major aim of this paper then is to introduce more appropriate analytic tools and illustrate their use in the present context. Qualitatively our results agree with those of the original analysis; our findings about interactions between effects, however, makes interpretation of these effects more subtle. We apply linear logistic modeling to counts of damaged embryos, using as covariates factors corresponding to exposure, laboratory, incubator, run, and measurements of background radiation. This facilitates estimation of the size of the effects. The effects of laboratory, incubator, and run are explored both as fixed and random effects. We find statistically significant exposure and laboratory effects, in accordance with the original study. However, we also find that the inter-laboratory variation in exposure effect is at least as large as the exposure effect itself. The presence of such effects fundamentally alters the interpretation of the fitted model, as is graphically presented.

Animals↗

PubMed1992

Cytopathology of malignant mesothelioma: a stepwise logistic regression analysis.

Twenty-four cytologic features, previously reported to be useful in the distinction of malignant mesothelioma, adenocarcinoma, and benign mesothelial proliferation in serous effusions were assessed. Forty-four cases of malignant mesotheliomas, 46 cases of metastatic adenocarcinomas, and 30 cases of benign mesothelial proliferations were examined for these parameters. When these cytologic features were subjected to a stepwise logistic regression analysis, five features were selected to distinguish malignant mesothelioma from adenocarcinoma. These were true papillary aggregates, multinucleation with atypia, cell-to-cell apposition, acinus-like structures, and balloon-like vacuolation, the latter two features being characteristic of adenocarcinoma. The four variables selected to distinguish malignant mesothelioma from benign mesothelial proliferations were nuclear pleomorphism, macronucleoli, cell-in-cell engulfment, and monolayer cell groups, the latter being a feature of benign proliferations. Using these selected variables, the logistic model correctly predicted 95.4% of cases of malignant mesothelioma versus 100% of adenocarcinoma and 100% of malignant mesotheliomas versus 90% of benign mesothelial proliferations. The results of regression analysis suggest that many of the previously described cytologic features are not important diagnostic discriminators.

Adenocarcinoma↗

PubMed1992

Pooling international health care expenditure data.

The purpose of this paper is twofold. The first is to analyse the statistical relationship between real health care expenditure per capita and aggregate income, public share in finance, age-dependency ratio and inflation. The second purpose deals with methodological problems involved in pooling health care expenditure data. The empirical work is based on pooled cross-sectional, time-series data for 22 OECD countries from 1972 to 1987. Public finance share and inflation were found to be associated with lower per capita health care expenditure. No consistent correlation was found between the age-dependency ratio and health care expenditure. Contrary to results of earlier studies, we found that health care expenditure does not appear to be income (GDP) elastic. However, the results do not appear to be robust to changes in the time periods and countries included.

Age Factors↗

PubMed1991

Seroepidemiological correlations of antibodies to human herpesviruses and human immunodeficiency virus type 1 in African patients.

A seroepidemiological evaluation of the humoral immune response against human herpes viruses was carried out in patients with and without HIV infection in Tanzania to study the role of these viruses as a cofactor in AIDS. Serum specimens were obtained from 321 outpatients and 100 healthy schoolchildren of a rural population in the Kagera Region, Tanzania, and from 149 inpatients of an urban population in Dar-es-Salaam, Tanzania. The data were analysed by logistic models taking into account demographic variables. The data obtained revealed no differences in the prevalence of antibodies to human herpes viruses between the different groups. Therefore, our study under the present conditions and the observed stages of AIDS does not suggest an influence of HIV infection on human herpesvirus infection or serologic response.

Acquired Immunodeficiency Syndrome↗

PubMed1992

Predicting genitourinary toxicity in patients receiving cisplatin-based combination chemotherapy: a Cancer and Leukemia Group B study.

Assessment of renal function prior to cisplatin chemotherapy has long been based on measurement of creatinine clearance by 24-hour urine collection (CrCmeas). Estimated creatinine clearance (CrCest) as calculated from the patient's age, weight, and serum creatinine level has been suggested as an adequate surrogate for CrCmeas, as it provides advantages of improved convenience, decreased cost, and possibly increased accuracy. We studied 847 patients receiving cisplatin-based chemotherapy on Cancer and Leukemia Group B (CALGB) protocols to determine whether the CrCmeas, CrCest, or serum creatinine value or the age of the patient would predict the subsequent genitourinary (GU) toxicity. Both CrCmeas (P = 0.001) and CrCest (P = 0.02) were predictive of subsequent grade 2+ GU toxicity, with CrCmeas being a slightly better predictor. Patient age also influenced subsequent GU toxicity, with the risk increasing with age (P = 0.0008). When patients were classified by age group and by CrCmeas, distinct subgroups were identified, with differences in the risk for grade 2+ GU toxicity ranging from 14% to 32%. Using a logistic model to assess the probability of grade 2+ GU toxicity, we found that an age of greater than or equal to 60 years (P = 0.005), a CrCmeas value of less than 75 ml/min (P = 0.004), and the risk characteristics of the individual cisplatin trial were important, whereas CrCest was not. Furthermore, CrCest proved to be a poor predictor of a CrCmeas value of less than 75 ml/min, "misclassifying" nearly half of the patients to a "lower-risk" subgroup. In summary, both CrCmeas and the patient's age independently provided predictive information concerning cisplatin GU toxicity. Our data support the continued clinical usefulness of determining the CrCmeas value prior to the administration of cisplatin-based chemotherapy to most patients.

Adult↗

PubMed1992

Sex differences in mental illness: a community study of the influence of physical health and sociodemographic factors.

This paper examines sex differences in psychiatric morbidity, using data from a community sample. The PSE-CATEGO-ID system was used to evaluate psychopathology. Six sociodemographic factors and physical illness were taken as independent variables. Females exhibit both a significantly higher psychiatric morbidity than males and a predominance of syndromes closely related to depression (SD; OD syndromes) and anxiety (GA; SA; TE; IT syndromes). Logistic modelling analysis, carried out separately for each sex, yielded different models. Psychiatric illness in men was best predicted by physical illness, unemployment and the interaction between the two. In contrast, physical illness emerged, in women, as the only factor exerting significant effects on psychiatric morbidity.

Adolescent↗

PubMed1992

Triglyceride levels and the risk of coronary artery disease: a view from Australia.

A prospective study of cardiovascular disease in elderly Australians commenced in 1988 in Dubbo, New South Wales. The study population comprised 1,237 men and 1,568 women aged > or = 60 years. The prevalence rates of coronary artery disease (CAD) and putative risk factors were examined cross-sectionally in the baseline data. The age-standardized rate of CAD was 23.8/100 men and 18.1/100 women. In a univariate analysis, the major risk factors for CAD were hypertension, diabetes, family history, reduced high-density lipoprotein (HDL) cholesterol levels, and increased triglyceride levels. The prevalence rate of CAD was examined in those with low-density lipoprotein (LDL):HDL ratios < 5.0 or > 5.0. Most notably in women, the CAD rate was 16/100 with an LDL.HDL ratio < or = 5.0 and 28/100 with an LDL.HDL ratio > 5.0. In the latter group, the rate was 21/100 in those with triglycerides < or = 2.3 mmol/liter and 36/100 in those with triglycerides > 2.3 mmol/liter. In a multiple logistic model that controlled for many potential risk factors or confounding variables, CAD in men was significantly predicted by age, hypertension (odds ratio = 1.40), family history (odds ratio = 2.05), and low HDL cholesterol (odds ratio = 0.78). Significant predictors in women were age, years of education (odds ratio = 0.82), hypertension (odds ratio = 1.45), family history (odds ratio = 1.77), serum triglycerides (odds ratio = 1.30), and low HDL cholesterol (odds ratio = 0.73). An independent gradient of CAD risk with increasing triglyceride levels and a similar gradient with decreasing HDL cholesterol levels were found in women.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1990

Sternotomy infection: poor prediction by acute phase response and delayed hypersensitivity.

Two hundred twenty-one consecutive adult cardiac surgical patients were examined prospectively for nutritional protein state, acute phase protein response, and delayed hypersensitivity reaction in an attempt to identify patients at high risk for the development of sternal wound infection, which occurred in 6 patients (2.7%). There was no significant correlation between preoperative nutritional protein concentrations (retinol-binding protein, prealbumin, and transferrin) and acute phase protein levels (C-reactive protein, alpha 1-acid glycoprotein, and complements B and C3), nor a statistically significant relationship between nutritional state or acute phase protein response and the development of sternal infection. Preoperative complement C3 levels were elevated, however, in 80.0% of those in whom sternal infections developed compared with 30.6% of those with well-healed wounds. Similarly, postoperative concentrations of alpha 1-acid glycoprotein were elevated in 80.0% of those in whom sternal infections developed compared with 28.6% of those with well-healed wounds. There was no correlation between delayed hypersensitivity and the risk of sternal infection, nor between preoperative nutritional protein and acute phase protein values. Seventy-three percent of patients were anergic on postoperative day 2. Stepwise logistic regression showed that age, body weight, preoperative intensive care unit stay, repeat median sternotomy, internal mammary artery grafting, postoperative hemorrhage, and postoperative cardiac arrest correlated with the development of sternal infection, whereas transfusion requirement, reexploration for bleeding, and the operation performed did not. We conclude that routine delayed hypersensitivity testing is of no value in predicting high-risk cardiac surgical patients when the anergy battery is placed on the preoperative day. Although statistically insignificant, possibly due to the small number of patients in whom sternal infection developed in this study (type II error), a larger study might find preoperative complement C3 and post-operative alpha 1-acid glycoprotein levels to be predictive of patients at risk for the development of sternal wound infection. The final logistic model for the predicted risk 2%) of sternal wound infection is: PREDSWC = exp(EQ)/1 + exp(EQ) where EQ = (0.38 x age) + (0.24 x weight) + (5.42 x preop ICU) + (4.39 x redo) + (7.14 x IMA) + (4.49 x hemorrhage) + (8.81 x arrest) - 62.72, and where preop ICU, redo, hemorrhage, and arrest are defined as yes (1) or no (0), IMA-is defined as 0, 1, or 2, age is in years, and weight is in kilograms.

Acute-Phase Proteins↗

PubMed1992

The association of individual allergen reactivity with respiratory disease in a national sample: data from the second National Health and Nutrition Examination Survey, 1976-80 (NHANES II).

The independent association of individual allergen reactivity with respiratory disease was evaluated with use of the second National Health and Nutrition Examination Survey, a sample of the U.S. white civilian population, ages 6 to 24 years (n = 4295). Eight, 1:20 wt/vol, 50% glycerol, unstandardized extracts were administered by prick puncture. Allergen reactivity was reported as the percent with a mean erythema diameter 10.5 mm or greater at 20 minutes. Only the prevalence of asthma and allergic rhinitis increased with the increasing number of positive allergen skin tests. The independent association of individual allergen reactivity with respiratory disease was quantified with logistic models that included other allergen reactivity, age, sex, smoking, and region. Asthma was associated with reactivity to house dust (odds ratio, 2.9; 95% confidence interval [CI] 1.7 to 5) and Alternaria (odds ratio, 5.1; 95% CI: 2.9 to 8.9). Allergic rhinitis was associated with reactivity to ragweed (odds ratio, 2.3; 95% CI: 1.5 to 3.3); ryegrass (odds ratio, 2.8; 95% CI: 1.8 to 4.3); house dust (odds ratio, 2.5; 95% CI: 1.6 to 3.9); Alternaria (odds ratio, 2.3; 95% CI: 1.5 to 3.4). Asthma only (without allergic rhinitis) was associated with dust and Alternaria. Allergic rhinitis only (without asthma) was associated with ryegrass, ragweed, and house dust. When both asthma and allergic rhinitis were present, only house dust and Alternaria remained associated. These findings highlight the association of specific allergens with upper and lower respiratory diseases and the interactions among coexisting respiratory diseases.

Adolescent↗

PubMed1992

Patient characteristics and the effect of three physician-delivered smoking interventions.

BACKGROUND: This paper investigates individual patient characteristics predicting differential response to each of three physician-delivered smoking interventions after 6 months. METHODS: Participants were 1,286 currently smoking patients seen by 196 medical and family practice residents in five primary care clinics affiliated with the University of Massachusetts Medical School. Of the participants, 57% were female, 92% were white, their average age was 35 years, and they smoked an average of 23 cigarettes per day. Physicians were trained to provide the following interventions: advice only (AO), a brief (< 10 min) patient-centered counseling intervention (CI), and counseling plus prescription of the nicotine-containing gum Nicorette (CI+NCG). The CI+NCG condition included NCG only when appropriate and if acceptable to the patient. Patients were randomized to one of these three physician-delivered intervention conditions. RESULTS: Overall, stratified univariate analyses revealed that AO produced consistently lower cessation rates across most subgroups (generally 9-13%) but was somewhat more effective for certain groups of lighter smokers. Relative to AO, CI was somewhat more effective (about 20-24%) for less addicted smokers, for those with more previous quit attempts, and for those with fewer close associates who smoke, but generally failed to produce higher quit rates for harder core smokers or for women. CI+NCG had an overall pattern of greater effectiveness for both more addicted and less addicted smokers, with the highest absolute levels of cessation (about 27-30%) among less dependent smokers. Women in this group had cessation rates (20.6%) comparable to those of men (23.6%). Condition-stratified logistic regression analyses, controlling for a wide range of covariates, revealed associations similar to those observed in the univariate analyses: An overall logistic model in which intervention conditions were fitted as dummy variables produced the following significant main effects: sex, years smoked, contact with other smokers, symptoms, and CI+NCG condition. Significant interactions were observed for both CI and CI+NCG and smoking when feeling too ill to continue normal activities and CI+NCG and amount smoked. CONCLUSIONS: We observed significant main effects on cessation of variables related to addiction, sex, social factors, and physician counseling interventions. Specific interactions were observed between reported smoking when feeling ill and each of the counseling interventions as well as by amount smoked in the CI+NCG condition.

Adult↗

PubMed1992

Autoantibody against oxidised LDL and progression of carotid atherosclerosis.

Oxidative modification of LDL renders it immunogenic and autoantibodies to epitopes of oxidised LDL, such as malondialdehyde (MDA)-lysine, are found in serum and recognise material in atheromatous tissue. However, there has been no prospective study to assess the importance of oxidised LDL among patients with vascular disease. We compared the titre of autoantibodies to MDA-modified LDL and native LDL in baseline serum samples of 30 eastern Finnish men with accelerated two-year progression of carotid atherosclerosis and 30 age-matched controls without progression. Neither group had specific antibody binding to native LDL. A titre was defined as a ratio of antibody binding to MDA-LDL/binding to native LDL. Cases had a significantly higher titre to MDA-LDL (2.67 vs 2.06, p = 0.003). Cases also had a greater proportion of smokers (37% vs 3%), higher LDL cholesterol (4.2 mmol/l vs 3.6 mmol/l), and higher serum copper concentration (1.14 mg/l vs 1.04 mg/l). Even after adjusting for these variables and the severity of baseline atherosclerosis, the difference in antibody titre remained significant in a multifactorial logistic model (p = 0.031). Thus, the titre of autoantibodies to MDA-LDL was an independent predictor of the progression of carotid atherosclerosis in these Finnish men. Our data provide further support for a role of oxidatively modified LDL in atherogenesis.

Adult↗

PubMed1992

Effect of ambient oxygen concentration upon the acute toxicity of chlorophenols and heavy metals to the groundwater copepod Parastenocaris germanica (Crustacea).

Acute static toxicity experiments have been performed under normoxic and hypoxic conditions. The test animals used were adults of the groundwater-adapted copepod Parastenocaris germanica. The animals originated from a sandy, gravelly phreatic aquifer of the Meuse valley in The Netherlands. Toxicants applied were pentachlorophenol, 3,4-dichlorophenol, zinc, and cadmium. The results were statistically evaluated by a log-logistic model. LC50 and LC5 values with 95% confidence limits were calculated. Response models of application under both oxygen conditions were compared. The influence of ambient oxygen concentration on sensitivity appeared to be very small; only in the case of pentachlorophenol were hypoxic and normoxic models slightly but significantly different. Comparisons with the sensitivity of other organisms are made and the results are discussed against the specific physiological adaptations of the organisms to groundwater conditions.

Animals↗