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J S Kaufman

Publications and source records attributed to J S Kaufman.

At least 19 recordsLinked to original sources
PubMed2001

Commentary: considerations for use of racial/ethnic classification in etiologic research.

Numerous authors have critiqued the use of race as an etiologic quantity in medical research. Despite this criticism, the use of variables encoding racial/ethnic categorization has increased in epidemiology, and most researchers agree that important variation in disease risk is captured by this classification system. Previous discussions have generally neglected to articulate guidelines for appropriate use of racial/ethnic information in etiologic research. The authors summarize the logical, conceptual, and practical problems associated with the "ethnic paradigm" as currently applied in biomedical sciences and offer a set of methodological recommendations toward more valid use of racial/ethnic classification in etiologic studies. These suggested guidelines address issues of variable definition, study design, and covariate control, providing a consistent foundation for etiologic research programs that neither ignore racial/ethnic disease disparities nor obfuscate the nature of these disparities through inappropriate analytical approaches. This methodological analysis of racial/ethnic classification as an epidemiologic quantity provides a formal basis for a focus on racism (i.e., social relations) rather than race (i.e., innate biologic predisposition) in the interpretation of racial/ethnic "effects."

Causality↗
PubMed2001

Diagnostic value of iron indices in hemodialysis patients receiving epoetin.

BACKGROUND: Iron deficiency remains a common cause of hyporesponsiveness to epoetin in hemodialysis patients. However, considerable controversy exists regarding the best strategies for diagnosis and treatment. METHODS: As part of a multicenter randomized clinical trial of intravenous versus subcutaneous administration of epoetin, we made monthly determinations of serum iron, total iron binding capacity, percentage transferrin saturation, and serum ferritin. If a patient had serum ferritin <100 ng/mL or the combination of serum ferritin <400 ng/mL and a transferrin saturation <20%, he/she received parenteral iron, given as iron dextran 100 mg at ten consecutive dialysis sessions. We analyzed parenteral iron use during the trial, the effect of its administration on iron indices and epoetin dose, and the ability of the iron indices to predict a reduction in epoetin dose in response to parenteral iron administration. RESULTS: Eighty-seven percent of the 208 patients required parenteral iron to maintain adequate iron stores at an average dose of 1516 mg over 41.7 weeks, or 36 mg/week. Only two of 180 patients experienced serious reactions to intravenous iron administration. Two thirds of the patients receiving parenteral iron had a decrease in their epoetin requirement of at least 30 U/kg/week compared with 29% of patients who did not receive iron (P = 0.004). The average dose decrease 12 weeks after initiating iron therapy was 1763 U/week. A serum ferritin <200 ng/mL had the best positive predictive value (76%) for predicting a response to parenteral iron administration, but it still had limited clinical utility. CONCLUSIONS: Iron deficiency commonly develops during epoetin therapy, and parenteral iron administration may result in a clinically significant reduction in epoetin dose. The use of transferrin saturation or serum ferritin as an indicator for parenteral iron administration has limited utility.

Adult↗
PubMed2001

Proteinuria in obstructive sleep apnea.

BACKGROUND: Previous studies have reported an association between obstructive sleep apnea (OSA) and proteinuria, but are limited in their ability to assess proteinuria accurately, to adjust for confounders such as obesity, or to exclude confidently underlying renal disease in patients with OSA and nephrotic-range proteinuria. METHODS: The spot urine protein/creatinine ratio was measured in a prospective consecutive series of 148 patients referred for polysomnography who were not diabetic and had not been treated previously for OSA. The urine protein/creatinine ratio was compared across four levels of OSA severity, based on the frequency of apneas and hypopneas per hour: <5 (absent), 5 to 14.9 (mild), 15 to 29.9 (moderate), and > or =30 (severe). RESULTS: The median level of urine protein/creatinine ratio in all categories of OSA was <0.2 (range 0.03 to 0.69; median 0.06 in patients with normal apnea hypopnea index, 0.06, 0.07, 0.07 in patients with mild, moderate, and severe OSA, respectively). Eight subjects had a urine protein/creatinine ratio greater than 0.2. Univariate analysis showed a significant association between urine protein/creatinine ratio and older age (P < 0.0001), hypertension (P < 0.0001), coronary artery disease (P = 0.003), and arousal index (P = 0.003). Body mass index (P = 0.16), estimated creatinine clearance (P = 0.17), and apnea hypopnea index (P = 0.13) were not associated with the urine protein/creatinine ratio. In multiple regression analysis, only age and hypertension were independent positive predictors of the urine protein/creatinine ratio (P < 0.0001, R2 = 0.17). CONCLUSION: Clinically significant proteinuria is uncommon in sleep apnea. Nephrotic range proteinuria should not be ascribed to sleep apnea and deserves a thorough renal evaluation.

Adult↗
PubMed2001

Assessment of structured socioeconomic effects on health.

Social epidemiologists study effects of variables such as education or income on health outcomes. Because other factors may influence both the exposure and the outcome, adjustments are commonly made in an effort to estimate the "independent" effect of exposure. The validity of common adjustment strategies when estimating the outcome distribution under hypothetical interventions of the exposure is potentially compromised by structured relations between covariates, observed and unobserved. These considerations of covariate structure may be particularly important for the study of "distal" socioeconomic factors that affect health through specified intermediates, therefore making standard adjustments in social epidemiology potentially problematic. Two related approaches have been proposed for defining and estimating causal effects in light of covariate structure: Robins' g-computation algorithm and Pearl's non-parametric structural equations. We review the conceptual foundation for these techniques, and provide a heuristic example using data from the National Longitudinal Mortality Study (NLMS) to demonstrate the extent to which selected causal effects (contrasts between hypothetical intervention regimens) are sensitive to structured relations among measured and unmeasured covariates, even in very simple systems.

Causality↗
PubMed2000

The natural history of incidental renal artery stenosis in patients with aortoiliac vascular disease.

PURPOSE: To examine the association between incidentally discovered renal artery stenosis and deterioration of renal function as determined by the change in serum creatinine concentration over time. SUBJECTS AND METHODS: We performed a retrospective review of consecutive patients who underwent aortography for aortoiliac vascular disease. Angiograms were reviewed for renal artery stenosis, defined as a narrowing of at least 20% compared with adjacent normal renal artery. For patients with at least 180 days of subsequent follow-up, the change in serum creatinine concentration per year was compared in patients who had or did not have renal artery stenosis. RESULTS: Of the 201 patients, 96 (48%) had some degree of renal artery stenosis in one or both renal arteries, including 53 (26%) who had at least one stenosis > or= 50% and 40 (20%) who had bilateral stenoses. The only clinical predictor of renal artery stenosis was a history of coronary artery disease (odds ratio = 2.0, 95% confidence interval: 1.2 to 3.8, P = 0.001). Among the 174 patients with > or =180 days of follow-up, there was no statistically significant difference (P = 0.88) in the mean change in serum creatinine concentration per year in the 78 patients with renal artery stenosis (0.06+/-0.33 mg/dL per year) as compared with the 96 patients without renal artery stenosis (0.06+/-0.22 mg/dL per year). Grouping the patients by the maximal percentage of stenosis did not reveal any difference in the mean changes in serum creatinine concentration per year. CONCLUSIONS: Although renal artery stenosis is a common incidental finding in patients with atherosclerotic vascular disease, it is an uncommon cause of progressive renal disease.

Aged↗
PubMed2000

A pharmacodynamic study of clopidogrel in chronic hemodialysis patients.

Combination antiplatelet agents, particularly aspirin and ticlopidine, have found increased use in the prevention of arterial thrombosis. Clopidogrel, a thienopyridine derivative, like ticlopidine was recently approved by the U.S. Food and Drug Administration (FDA) for the reduction of ischemic events in patients with myocardial infarction, stroke, or peripheral arterial disease and appears to have much less hematologic toxicity than ticlopidine has. Thrombosis of hemodialysis access grafts is a major cause of morbidity in this patient population. Combination antiplatelet agents may be particularly useful in the prevention of hemodialysis access graft thrombosis. In preparation for such a study, we have performed a pharmacodynamic study of the platelet inhibitory effects of clopidogrel in patients on maintenance hemodialysis. Nine chronic hemodialysis patients were studied. Baseline platelet aggregation studies were performed, after which the subjects were begun on clopidogrel 75 mg daily. Platelet aggregation studies were repeated after 14 days of therapy. Drug was stopped and a final set of platelet aggregation studies were performed 7 days later. Because clopidogrel acts by inhibiting adenosine diphosphate (ADP)-induced platelet aggregation, we used ADP as the agonist in the platelet aggregation studies. We also measured the time required to achieve hemostasis after removing the dialysis needles at the termination of a dialysis session. Patients were carefully monitored for any adverse reaction to clopidogrel. Fourteen days' treatment with clopidogrel inhibited ADP-induced platelet aggregation from 48 to 23% with ADP 2 microM (P=0.0113), from 59 to 38% with ADP 5 microM (P=0. 0166), and from 66 to 44% with ADP 10 microM (P=0. 0172). This inhibition of platelet aggregation was reversed 7 days after stopping clopidogrel. Clopidogrel administration did not affect the time required to achieve hemostasis after removal of the dialysis needles. No adverse reactions were noted. No patient had evidence of bleeding, rash or gastro-intestinal (GI) upset. Clopidogrel inhibits ADP-induced platelet aggregation in subjects receiving chronic maintenance hemodialysis. The magnitude of inhibition is similar to that reported in nonuremic subjects with atherosclerosis. This inhibition is reversible within 7 days of discontinuing the drug. No adverse reactions to the drug were noted in this short-term (14-day) trial.

Adenosine Diphosphate↗
PubMed2000

Hypertension in a black population: prevalence and biosocial determinants of high blood pressure in a group of urban Nigerians.

AIMS: To define the prevalence of hypertension, a major cause of morbidity and mortality in blacks, and related biosocial factors in an urban African population group. METHODS: The setting was that of a civil service population in Ibadan, a major city in Southwestern Nigeria. Nine hundred and ninety-eight civil servants selected by multistage sampling participated in the survey. Biosocial data including smoking history, alcohol use and level of physical activity; anthropometry, blood pressure and plasma glucose measurements were obtained. Diagnosis of hypertension was based on blood pressure of > or =160/95 mm Hg or known hypertensive on treatment. RESULTS: The overall prevalence rate of hypertension was 10.3% (CI, 8.4%, 12.2%), rates of 13.9% and 5.3% were obtained in men and women respectively in spite of a much higher rate of generalised obesity in the latter. Hypertension was associated with higher salary grade level, but there was no relationship found with regular exercise, smoking and alcohol. Obesity (body mass index (BMI) > or =30 kg/m2) was associated with hypertension only in women. A two-sided t-test demonstrated age, waist circumference, waist to hip ratio (WHR) and plasma glucose level as significant variables. In multivariate ANOVA models of systolic blood pressures, age, male sex and BMI were highly significant factors (P < 0.0001) and plasma glucose was also significant (P < 0.016); the same variables (except plasma glucose) were associated with diastolic blood pressures. In logistic regression models the variables which predicted hypertension were WHR, plasma glucose, age, sex and family history of diabetes. CONCLUSIONS: Prevalence of hypertension in the study was comparable to recently reported rates in urban Nigeria and similar populations in Africa. The biosocial determinants of hypertension in the urban black population were age, male gender, higher socio-economic status, BMI, plasma glucose, generalised and central adiposity. Regional fat distribution was a stronger predictor of hypertension than generalised obesity in the population.

Adult↗
PubMed2000

Looking back on "causal thinking in the health sciences".

It has now been over a quarter of a century since the publication of Mervyn Susser's Causal Thinking in the Health Sciences (1973, Oxford University Press), the first book-length treatment of causal reasoning and inference in our field. Major contributions of this work were its holistic focus on the origins of health outcomes in the context of ecologic systems and its invigoration of the literature on causal criteria in epidemiology. Although a recent resurgence of interest in social context has revivified many points made by Susser, a formal basis for causal analysis consistent with this ecologic perspective has failed to emerge in public health research. Susser's discussion of causal criteria, on the other hand, helped spur a vigorous dialogue that has persisted unabated to the present day. Although the basic outline of the criteria has evolved little, their applications, interrelations, and relative contributions to causal judgments have been the subject of continued and sometimes contentious debate.

Causality↗
PubMed2000

A common polymorphism in methionine synthase reductase increases risk of premature coronary artery disease.

BACKGROUND: Methionine synthase reductase (MTRR) catalyzes the regeneration of methylcobalamin, a cofactor of methionine synthase, an enzyme essential for maintaining adequate intracellular pools of methionine and tetrahydrofolate, as well as for maintaining homocysteine concentrations at nontoxic levels. We recently identified a common A-->G polymorphism at position 66 of the cDNA sequence of MTRR; this variant was associated with a greater than normal risk for spina bifida in the presence of low levels of cobalamin. OBJECTIVE: To investigate whether the polymorphism was associated with alterations in levels of homocysteine, folate, and vitamin B12, and with risk of developing premature coronary artery disease (CAD), in a population of individuals presenting for cardiac catheterization procedures. METHODS: We screened 180 individuals aged < 58 years with angiographically documented coronary-artery occlusions or occlusion-free major arteries for the presence of the 66A-->G MTRR polymorphism using a polymerase-chain-reaction-based assay. RESULTS: We identified a trend in risk of premature CAD across the genotype groups (P = 0.03) with a sex-adjusted relative risk of premature CAD equal to 1.49 (95% confidence interval 1.10-2.03) for the GG versus AA genotype groups. There was no difference in fasting levels of plasma total homocysteine, serum folate, and vitamin B12 among the three MTRR genotypes. CONCLUSIONS: Our findings suggest that the GG genotype of MTRR is a significant risk factor for the development of premature CAD, by a mechanism independent of the detrimental vascular effects of hyperhomocysteinemia. This association needs to be confirmed in other studies.

Age Factors↗
PubMed2000

The phosphoprotein Op18/stathmin is differentially expressed in ovarian cancer.

To identify potential prognostic indicators of ovarian cancer and identify targets for therapeutic strategies, mRNA differential display was used to analyze gene expression differences in normal, benign, and cancerous ovarian tissue. One cDNA isolated by this technique, Op18/stathmin, is a highly conserved gene that is reported to have many different functions within a cell, including signal transduction, control of the cell cycle, and the regulation of microtubules. Quantitative Northern blot analysis of 12 malignant ovarian samples, 8 benign ovarian tumors, and 10 normal ovarian tissue samples demonstrated overexpression of Op18/stathmin mRNA in the malignant cancers. Immunohistochemistry showed an apparent overexpression of Op18/stathmin protein level and an association with proliferating cells.

Blotting, Northern↗
PubMed2000

The Idikan adult mortality study.

The Idikan adult mortality study is designed to explore the usefulness of the verbal autopsy methodology in the determination of cause-specific adult mortality. Such data have been largely unavailable in developing countries. Members of a stable urban community (4333 adults) were registered in their family units and followed up every 3 months to ascertain deaths, exits and new entries to the study population. Deaths were investigated by means of a verbal autopsy, which was administered by a trained interviewer to the relative closest to the decedent. Two physicians independently studied the results and assigned a cause of death, and these were then confirmed or resolved by a senior physician colleague. Hospitals where deaths occurred were visited and assignable cause of death was obtained where available and compared with the cause assigned by verbal autopsy. Only 8 of the 60 investigated deaths were confirmed to have occurred in a hospital in the first 2 years of the study. The cause of death assigned by verbal autopsy agreed moderately both between the independent coders as well as with the hospital assigned cause of death using the Kappa statistics for agreement beyond chance. We therefore concluded that verbal autopsies appear moderately useful for adult death statistics (Kappa = 0.23 to 0.1). Accumulation of more hospital deaths is needed, however, to make more definite conclusions about the validity of the technique.

Adolescent↗
PubMed1999

Seeking causal explanations in social epidemiology.

Social factors are associated with a wide variety of health outcomes. Social epidemiology has successfully used the traditional methods of surveillance and description to establish consistent relations between social factors and health status. Epidemiology as an etiologic science, however, has been largely ineffective in moving toward causal explanations for these observed patterns. Using the counterfactual approach to causal inference, the authors describe several fundamental problems that often arise when researchers seek to infer explanatory mechanisms from data on social factors. Contrasts that form standard causal effect estimates require implicit unobserved (counterfactual) quantities, because observational data provide only one exposure state for each individual. Although application of counterfactual arguments has successfully advanced etiologic understanding in other observational settings, the particular nature of social factors often leads to logical contradictions or misleading inferences when investigators fail to clearly articulate the counterfactual contrasts that are implied. For example, because social factors are often attributes of individuals and are components of structured social relations, random assignment is not plausible even as a hypothetical experiment, making typical epidemiologic contrasts inappropriate and the inference equivocal at best. Accordingly, more deliberate and creative approaches to causal inference in social epidemiology are required. Infectious disease epidemiology and systems analysis provide examples of approaches to causal inference that can be used when statistical mimicry of simple experimental designs is not tenable. In an era of increasing social inequality, valid approaches for the study of social factors and health are needed more urgently than ever.

Black or African American↗
PubMed1999

Diabetes in the Caribbean: results of a population survey from Spanish Town, Jamaica.

AIMS: To characterize the prevalence of diabetes and associated risk attributes in the Jamaican population. METHODS: A random population sample was recruited by door-to-door canvassing (n = 1303). A final participation of 60% was achieved. Oral glucose tolerance testing was conducted after an overnight fast and standard anthropometric and demographic data were collected. RESULTS: The prevalence of Type 2 diabetes mellitus was 9.8% (95% confidence interval (CI) 7.2-12.4) among men and 15.7% (95% CI 13.1-18.3) among women with an overall prevalence of 13.4% (95% CI 11.5-15.2). Impaired glucose tolerance was found among 12.3% of men and 14.7% of women. The sex patterns were consistent with a fourfold excess of obesity in women compared to men. The odds ratios for diabetes, fourth vs. first quartiles were 5.42 (95% CI 2.02-16.88) in men and 3.32 (95% CI 1.73-6.63) in women for body mass index (BMI) and 17.39 (95% CI 3.86-78.27) in men and 5.48 (95% CI 2.84-11.00) in women for WHR in a logistic model controlling for age. The population attributes risk percentage, for diabetes, of being overweight and having waist-to-hip ratio (WHR) greater than the median (0.80) were 66% and 80%, respectively. The contribution of central obesity, as characterized by WHR, was also significant in sex-specific multivariate models that included age and BMI. Prevalent hypertension and family history of diabetes were likewise associated with increased odds of having the disease. CONCLUSIONS: The prevalence of diabetes in Jamaica now exceeds that observed among European-origin populations and reflects the emerging epidemic of obesity. The excess risk for this population could not be attributed entirely to relative weight. The pronounced sexual dimorphism in diabetes prevalence most likely reflects the substantial excess of obesity among women compared to men. Like many other island nations, Caribbean societies now appear to be at substantial risk of diabetes.

Aged↗
PubMed1999

Tuberculosis exposure risk in emergency medicine residents.

OBJECTIVES: To assess purified protein derivative (PPD) test surveillance and respiratory protection practices of emergency medicine (EM) residents, along with the prevalence of PPD test conversion and the development of active tuberculosis (TB) in EM residents. METHODS: The study instrument was an anonymous, self-reporting, multiple-choice survey administered to U.S. and Canadian EM residents. It was distributed for voluntary completion in conjunction with the American Board of Emergency Medicine's annual in-service examination, which was administered February 25, 1998. RESULTS: A total of 89.3% (n = 2,985) of residents eligible to complete the survey completed at least part of it. The majority of residents are PPD-tested once a year. The prevalence of PPD test conversions in EM residents was between 1.4% (36/2,575) and 2.0% (52/2,575). Of the residents who PPD test-converted, the ED was most often the perceived area of TB source exposure (n = 15). Two residents (0.08%) reported having developed active TB, including chest radiographic findings or clinical infection, which equals a 0.14% (95% CI = 0.005 to 0.31) risk of developing active TB over a three-year residency. Half of all the residents do not routinely wear National Institute for Occupational Safety and Health (NIOSH)-approved particulate filtration respirator (PFR) masks in patient encounters at risk for TB exposure. While more than a third of EM residents have not undergone fit testing for a NIOSH-approved PFR mask, the lack of routine easy availability of such masks is the most common reason they are not routinely worn by EM residents during at-risk encounters for TB transmission. CONCLUSIONS: Most surveillance PPD testing of EM residents is performed at intervals recommended by the CDC. TB control programs at institutions sponsoring EM residencies need to improve both compliance with PFR mask fit testing by EM residents and availability of approved PFR masks in appropriate areas of the ED. Despite poor compliance with personal respiratory protection in ED patient encounters at risk for TB transmission, the risk of an EM resident's developing active TB over a three-year residency is low.

Emergency Medical Services↗