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Biomedical subjects

D G Kleinbaum

Publications and source records attributed to D G Kleinbaum.

At least 19 recordsLinked to original sources
PubMed1997

Local and remote sustained trigger point therapy for exacerbations of chronic low back pain. A randomized, double-blind, controlled, multicenter trial.

STUDY DESIGN: A randomized, double-blind, controlled, multicenter trial was conducted. OBJECTIVES: To assess the efficacy of neuroreflexotherapy in the management of low back pain. SUMMARY AND BACKGROUND DATA: Neuroreflexotherapy consists of temporary implantation of epidermal devices in trigger points in the back and referred tender points in the ear. METHODS: The rheumatology and rehabilitation departments of three teaching hospitals in Madrid recruited 78 patients with chronic low back pain. These patients were randomly assigned to the control group (37 patients) or to the treatment group (41 patients). Patients in the treatment group underwent one neuroreflexotherapeutic intervention. The control group received sham treatment consisting of placement of the same number of epidermal devices within a 5-cm radius of the target zones. Patients from both groups were allowed to continue drug treatment as previously prescribed. The use of medications during the trial was recorded. RESULTS: Patients underwent clinical evaluations on three occasions: within 5 minutes before intervention, within 5 minutes after intervention, and 45 days later. The preintervention assessment was carried out by the physician from each hospital department who included the patient in the study. Each of the two follow-up assessments were carried out independently by two of three physicians who had no connection with the research team. Patients in the treatment group showed immediate lessening of pain compared with the results in patients in the control group. The pain relief was clinically relevant and statistically significant, and it persisted up to the end of the trial. CONCLUSIONS: Neuroreflexotherapy intervention seems to be a simple and effective treatment for rapid amelioration of pain episodes in patients with chronic low back pain. At this time, the duration of pain relief beyond 45 days has not been evaluated.

Adult↗
PubMed1997

Regression models for ordinal responses: a review of methods and applications.

BACKGROUND: Epidemiologists are often interested in estimating the risk of several related diseases as well as adverse outcomes, which have a natural ordering of severity or certainty. While most investigators choose to model several dichotomous outcomes (such as very low birthweight versus normal and moderately low birthweight versus normal), this approach does not fully utilize the available information. Several statistical models for ordinal responses have been proposed, but have been underutilized. In this paper, we describe statistical methods for modelling ordinal response data, and illustrate the fit of these models to a large database from a perinatal health programme. METHODS: Models considered here include (1) the cumulative logit model, (2) continuation-ratio model, (3) constrained and unconstrained partial proportional odds models, (4) adjacent-category logit model, (5) polytomous logistic model, and (6) stereotype logistic model. We illustrate and compare the fit of these models on a perinatal database, to study the impact of midline episiotomy procedure on perineal lacerations during labour and delivery. Finally, we provide a discussion on graphical methods for the assessment of model assumptions and model constraints, and conclude with a discussion on the choice of an ordinal model. The primary focus in this paper is the formulation of ordinal models, interpretation of model parameters, and their implications for epidemiological research. CONCLUSIONS: This paper presents a synthesized review of generalized linear regression models for analysing ordered responses. We recommend that the analyst performs (i) goodness-of-fit tests and an analysis of residuals, (ii) sensitivity analysis by fitting and comparing different models, and (iii) by graphically examining the model assumptions.

Epidemiologic Methods↗
PubMed1995

Basic models for disease occurrence in epidemiology.

BACKGROUND: One of the epidemiologist's most basic tasks is estimation of disease occurrence. To perform this task, the epidemiologist frequently models variability in disease occurrence using one of three distributions--the binomial, the Poisson or the exponential distribution. Although epidemiologists often use them and their properties appear in standard texts, we know of no text or review that compares and contrasts epidemiological application of these distributions. METHODS: In this commentary, we discuss these three basic distributions. We note key assumptions as well as limitations, and compare results from analyses based on each distribution. RESULTS AND CONCLUSIONS: We illustrate that the three distributions, although superficially different, often lead to similar results. We argue that epidemiologists should often obtain similar results regardless of which distribution they use. We also point out that application of all three distributions can be inappropriate if assumptions of independence or homogeneity of risks fail to hold. Finally, we briefly review how these basic distributions can be used to justify use of other distributions, such as the Gaussian distribution, for studying disease-exposure associations.

Binomial Distribution↗
PubMed1993

Methadone dose and heroin use during maintenance treatment.

A retrospective study examined the association between methadone dose and in-treatment heroin use as measured by fixed-interval urine testing in a cohort of 62 patients admitted to an Australian maintenance program. Urinalysis and methadone dose data were collected on subjects for a maximum two years and were analysed using Zeger & Liang's (1986) method for modelling longitudinal data. While allowing for patient descriptors and the time period in which urine samples were collected, the relative odds of using heroin were reduced by 2% for every 1 mg increase in the maintenance dose of methadone. It is estimated that the odds of patients maintained on 40 mg of methadone using heroin were 2.2 times those of patients maintained on 80 mg.

Adult↗
PubMed1993

The health effects of swimming at Sydney beaches. The Sydney Beach Users Study Advisory Group.

OBJECTIVES: The purpose of the study was to determine the health risks of swimming at ocean beaches in Sydney, Australia. METHODS: From people attending 12 Sydney beaches in the period from December 5, 1989 to February 26, 1990, we recruited a cohort of 8413 adults who agreed to participate in this study. Of these, 4424 were excluded either because they had been swimming in the previous 5 days or because they reported a current illness. Of the remainder, 2839 successfully completed a follow-up telephone interview conducted within 10 days after recruitment. We recorded reported respiratory, gastrointestinal, eye, and ear symptoms and fever that occurred within the 10 days between initial interview on the beach and the follow-up interview. RESULTS: A total of 683 participants (24.0%) reported experiencing symptoms in the 10 days following initial interview. Of these, 435 (63.7%) reported respiratory symptoms. Swimmers were almost twice as likely as nonswimmers to report symptoms. There was a linear relationship between water pollution and all reported symptoms with the exception of gastrointestinal complaints. CONCLUSIONS: Swimmers at Sydney ocean beaches are more likely to report respiratory, ear, and eye symptoms than beachgoers who do not swim. The incidence of these symptoms increases slightly with increasing levels of pollution.

Adolescent↗
PubMed1993

Clinic policy and retention in methadone maintenance.

Advantage was taken of a natural experiment to investigate the relationship of clinic objectives and procedures with retention in methadone maintenance. Assessment, maximum dose, and time in treatment data on 238 patients were summarized using Cox regression. While allowing for patient descriptors and maximum dose of methadone, those subjects assigned to a strongly abstinence-oriented program were 26% (95% C.I., 18 to 33%), 98% (66 to 137%), 213% (132 to 322%), and 393% (224 to 651%) more likely to leave treatment in the first, second, third, fourth 6 months of treatment, respectively, than those subjects assigned to a more laissez-faire program.

Adult↗
PubMed1991

Interpreting the literature in obstetrics and gynecology: I. Key concepts in epidemiology and biostatistics.

The proper interpretation of research findings in obstetrics and gynecology increasingly requires some understanding of epidemiology and biostatistics. The disciplines of epidemiology and biostatistics are inextricably related; the goal of epidemiology is accurate measurement of the relationship between an exposure and a disease, and statistical methods are required for achieving that objective. Most epidemiologic studies in the obstetrics and gynecology literature can be classified as 1) cross-sectional, 2) case-control, or 3) cohort (follow-up) studies. The 2 x 2 table represents the basic analytic format for all three types of epidemiologic studies. Information from this table can be used to estimate both the magnitude of the exposure-disease relationship and the relative likelihood that chance explains study findings. Accurate measurement of the relationship between an exposure and a disease can be impeded by two major sources of error: bias and chance. In broad terms, biases can be classified as those related to 1) selection, 2) information, and 3) the presence of extraneous variables. Because biases in epidemiologic studies distort measurements, they must be identified, characterized, and, if possible, avoided. When biases cannot be avoided, knowledge of their likely impact on study findings must be assessed. The role of chance is evaluated by statistical testing of the null hypothesis, ie, the hypothesis that two factors are not associated.(ABSTRACT TRUNCATED AT 250 WORDS)

Bias↗
PubMed1991

Interpreting the literature in obstetrics and gynecology: II. Logistic regression and related issues.

The goal of epidemiology is accurate measure of the relationship between an exposure and a disease of interest. The control of covariates of the exposure-disease relationship is required to obtain a valid measure. Two types of covariates, confounders and effect modifiers, must be considered. Investigators can design studies to measure and control for the impact of both types of covariates. Design strategies for dealing with covariates include randomization, restriction, and matching. If the impact of a covariate is not eliminated by study design, it must be controlled for during study analysis by use of either stratification or mathematical modeling. Stratified analysis permits an assessment of the exposure-disease relationship for each category of relevant covariates. Although stratification is the best initial approach for controlling covariates, it is often impractical, particularly if more than one or two covariates must be controlled. Multivariate mathematical models are required if multiple covariates are to be controlled. Logistic regression is the mathematical modeling procedure most often used to analyze studies in obstetrics and gynecology. Although there are no uniform rules for building a proper model for regression analysis, useful general strategies are available. It must be emphasized that, though the use of mathematical modeling can control for multiple covariates and thereby improve the chance of obtaining an accurate measure of the exposure-disease relationship, it cannot "fix" data that result from a poorly designed or improperly conducted study.

Gynecology↗
PubMed1989

Ecology of passive smoking by young infants.

This study provides a detailed description of passive smoking by 433 infants (mean age 18 days) enrolled from a representative population of healthy neonates in central North Carolina during 1986 and 1987. Sixty-four percent (276) lived in households with smokers or had contact with nonhousehold smokers. During the week before data collection, two thirds (184) of these 276 infants reportedly had tobacco smoke produced in their presence. Seventy-five percent of smoking mothers smoked near their infants. The amount smoked by the mother near the infant correlated with the amount smoked near the infant by nonmaternal smokers. Cotinine, an indicator of smoke absorption, was found in the urine of 60% (258) of all study infants. The amount smoked in the infant's presence, as well as the amount smoked farther away from the infant, especially by the mother, were the most significant correlates of the urine cotinine concentration. The results of this study suggest that efforts to reduce passive smoking in young infants should emphasize the importance of the mother's smoking behavior, smoke produced anywhere in the home, and household social influences on smoking behavior near the infant.

Cotinine↗
PubMed1989

The association between depressive symptoms and mortality among older participants in the Epidemiologic Catchment Area-Piedmont Health Survey.

The association between depression and two-year mortality risk was assessed in 1,606 elderly community participants in the 1982-83 Epidemiologic Catchment Area-Piedmont Health Survey. Two depression measures were formed from the Diagnostic Interview Schedule (DIS) depressive symptom items. Neither measure was associated with mortality in univariate or multiple logistic regression analyses. The adjusted relative risk of mortality comparing the lowest to highest levels of a three-level depression variable was 0.9 (95% confidence interval = 0.5-1.4). Similar results were obtained with other versions of the depression variables, with each depressive symptom category, and within sex, chronic disease, widowhood status, and age groups. These results indicate that depression does not increase mortality in elderly adults, but the short follow-up, sample characteristics, and operationalization of depression may have affected this association.

Age Factors↗
PubMed1989

Psychologic distress as a predictor of mortality.

In a 12-year follow-up study of 610 persons (239 black and 371 white) in Evans County, Georgia, psychologic distress as measured by total score on the Health Opinion Survey, a 20-item questionnaire, was a predictor of mortality. The hazard ratio, comparing the 95th percentile score with the median, was 1.93 (97.5% confidence interval (CI) 1.42-2.62), controlling for age, race, and sex; there was no interaction with these variables. A purer measure of distress symptomatology, based on 18 of the questionnaire items, was also predictive of mortality. The hazard ratio was 1.94 (97.5% Cl 1.33-2.82), controlling for age, race, sex, and the item, "Do you have any sickness or illness problems at the present time?"; no interactions with the latter variables were found. This pattern was not affected in any major way by several modifications of the analyses: 1) controlling also for smoking, serum cholesterol, Quetelet index (weight (kg)/height (m)2), diastolic blood pressure, a social network index, and a social class index; 2) excluding persons with a diagnosis (in 1968) of chronic heart disease, angina pectoris, myocardial infarction, stroke, transient cerebral ischemic attach, or diabetes mellitus, or whose deaths were due to neoplastic disease; and 3) restricting the analyses to the last half of the follow-up period to explore the role of incipient or early physical illness in producing the association. With the restricted samples, confidence intervals included 1.00, which may be attributed to both the substantially smaller samples and the slightly reduced strength of the effect. The evidence is consistent with a causal role for psychologic distress, as measured by the Health Opinion Survey, in subsequent mortality rates.

Adult↗
PubMed1986

Social ties and mortality in Evans County, Georgia.

In an attempt to replicate Berkman and Syme's study of social networks and mortality in Alameda County, California, the authors investigated the relationship between a social network index and survivorship from 1967 to 1980 in the Evans County, Georgia, cohort. They constructed an index modeled after the Berkman Social Network Index and tested it in race- and sex-specific proportional hazards models for 2,059 subjects who were examined in 1967-1969 during the Evans County Cardiovascular Epidemiologic Study. The present study emphasized a priori specification of the social network index and statistical hypothesis test. Descriptive analyses were consistent with a modest social networks effect (e.g., hazard ratio (95 per cent confidence interval) of 1.6 (1.2-2.2) ). Among white males, the age-adjusted hazard ratio comparing the lowest to the highest value of our six-level index was 2.0 (1.2-3.4), but control for potential confounders (principally cardiovascular disease risk factors) reduced this value to 1.5 (0.8-2.6). The social networks effect among white females, black males, and black females was weaker and clearly nonsignificant. Exploratory analyses suggested that marital status, church activities, and an alternate social network index predicted survivorship, but not in a dose-response fashion. Reduced survivorship among older subjects with few social ties was the most important feature of the data.

Adolescent↗
PubMed1985

Oral contraceptive use and blood pressure in a German metropolitan population.

The relationship between blood pressure (BP) and oral contraceptive (OC) use in women has been examined with the data from the Munich Blood Pressure Study (MBS), a cross-sectional study with follow-up of a random sample of 3198 Munich citizens aged 30-69 (response rate 69.3%). Multiple linear and logistic regression analyses were run with BP as the dependent variable and age, OC use, obesity, alcohol consumption, and smoking habit as the independent variables. All second and third order interactions between the independent variables were tested during a backward stepping procedure. OC use appeared as a significant main effect in most of the analyses. The coefficient of the OC variable was about 3 in the linear regression analyses for both systolic BP and diastolic BP, indicating an increase of about 3 mmHg in the systolic and diastolic BP of the OC users. An analysis of the change in BP after one year in relation to change in OC user status has also been made. It was observed that women ceasing to use OC had a clear decrease in BP while those starting to use OC had on average an increase in BP.

Adult↗
PubMed1985

The Edgecombe County High Blood Pressure Control Program: III. Social support, social stressors, and treatment dropout.

In a hypertension prevalence survey of a stratified random sample of 1,000 households, 2,030 adults (aged 18 years and over) were interviewed and information on psychosocial variables collected. Among 359 hypertensives, there was a consistent relationship between indicators of difficulty in the social environment and dropout from treatment in women. Compared to those who remained in treatment, women who dropped out can be characterized as having less social support on the job, having less perceived spouse approval (if married), having a lower level of perceived access to supportive resources, and being more likely to report feeling pushed most or all of the time if they are homemakers. Relationships between indicators of social support and dropout from treatment in men were found only with support on the job, and for White men, with perceived friend approval.

Adult↗
PubMed1984

John Henryism and blood pressure differences among black men. II. The role of occupational stressors.

In this study, the effects of psychosocial job stressors on the resting blood pressure (BP) of 112 black male workers were examined. The subjects resided in a rural, poor, predominantly black community in eastern North Carolina. The job stressors included unemployment, lack of job security, lack of job success, the perception that wages earned were too low for the work performed (and inhibited anger about unfair wages), and the perception that being black had hindered chances for achieving job success. The effect-modifying influence of on-the-job social support, and John Henryism, on several of these relationships was also examined. For systolic blood pressure, a main effect was observed for job security, and an interaction effect was observed for employment status and time of day of interview. For diastolic blood pressure, significant interactions were observed for job success and John Henryism, and for job success and the perception that being black had hindered chances for achieving job success. These findings further clarify under what conditions John Henryism may be associated with higher BPs in this sample of black men. These findings also shed light on the emotional pathways through which selected job stressors may influence resting BPs in these men.

Adaptation, Psychological↗
PubMed1984

The Edgecombe County High Blood Pressure Control Program: I. Correlates of uncontrolled hypertension at baseline.

To guide the planning of a multifacetted hypertension control program in Edgecombe County, North Carolina, a baseline survey of a stratified (by township) random sample of 1,000 households was conducted. All adults (greater than or equal to 18 years) were interviewed and had their blood pressures (BP) measured. Five hundred thirty-nine individuals, 27 per cent of the survey population, had diastolic BP greater than or equal to 90 mm Hg or were receiving anti-hypertensive drug therapy. The 539 hypertensives were divided into seven subgroups reflecting successive stages in the control of hypertension based on the awareness, treatment, and control of their hypertension. Unaware hypertensives were further subdivided into three groups according to the recency of their last BP check, and those aware but untreated were subdivided by whether they had previously received treatment. The seven subgroups of hypertensives were compared, separately for women and men, with respect to sociodemographic characteristics, health behaviors, and health status. In general, the progression from undetected hypertension to treatment and control appeared to be associated with being older, female, and White. This progression was further associated with greater educational levels and higher family incomes among women and increasing self-reported morbidity among men. The implications for intervention of these and other described associations are discussed.

Adolescent↗