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Biomedical subjects

M J Klag

Publications and source records attributed to M J Klag.

At least 55 records · Page 3Linked to original sources
PubMed1997

Gout and risk for subsequent coronary heart disease. The Meharry-Hopkins Study.

BACKGROUND: Patients with gout are encountered frequently in clinical practice. Previous studies have suggested that hyperuricemia and gout may represent risk factors for coronary heart disease (CHD), the most common cause of death in American men. METHODS: Prospectively collected data from 2 longitudinal cohort studies of former medical students--371 black men in the Meharry Cohort Study and 1181 white men in the Johns Hopkins Precursors Study--were analyzed. The development of gout and of CHD was determined by physician self-report, and validated by using published criteria. The risk for CHD associated with gout was evaluated using Cox proportional hazards analysis. RESULTS: During a median follow-up of 30 years, there were 38 gout cases and 44 CHD events among the Meharry men, and 68 gout cases and 138 CHD events among the Hopkins men. Prior gout was not associated with an increased risk for incident CHD (relative risk = 1.20; 95% confidence interval, 0.37-3.92) among the Meharry men or among the Hopkins men (relative risk = 0.66; 95% confidence interval, 0.24-1.79). Multivariate analysis adjusted for known CHD risk factors did not alter these findings. CONCLUSION: These results, in black and white male physicians, do not suggest a role in men for targeting gout identification in the primary prevention of CHD.

Adult↗
PubMed1997

Effects of oral potassium on blood pressure. Meta-analysis of randomized controlled clinical trials.

OBJECTIVE: To assess the effects of supplementation with oral potassium on blood pressure in humans. DESIGN: Meta-analysis of randomized controlled trials. DATA SOURCES: English-language articles published before July 1995. STUDY SELECTION: Thirty-three randomized controlled trials (2609 participants) in which potassium supplementation was the only difference between the intervention and control conditions. DATA EXTRACTION: Using a standardized protocol, 2 of us independently abstracted information on sample size, duration, study design, potassium dose, participant characteristics, and treatment results. RESULTS: By means of a random-effects model, findings from individual trials were pooled, after results for each trial were weighted by the inverse of its variance. An extreme effect of potassium in lowering blood pressure was noted in 1 trial. After exclusion of this trial, potassium supplementation was associated with a significant reduction in mean (95% confidence interval) systolic and diastolic blood pressure of -3.11 mm Hg (-1.91 to -4.31 mm Hg) and -1.97 mm Hg (-0.52 to -3.42 mm Hg), respectively. Effects of treatment appeared to be enhanced in studies in which participants were concurrently exposed to a high intake of sodium. CONCLUSIONS: Our results support the premise that low potassium intake may play an important role in the genesis of high blood pressure. Increased potassium intake should be considered as a recommendation for prevention and treatment of hypertension, especially in those who are unable to reduce their intake of sodium.

Administration, Oral↗
PubMed1997

History of hypertension in patients treated for end-stage renal disease.

OBJECTIVES: To describe patterns of hypertension history in patients with various types of end-stage renal disease (ESRD) and in persons with normal kidney function; and to identify risk factors for the diagnosis 'hypertensive ESRD'. DESIGN: A case-control study. SETTING: Population-based. PARTICIPANTS: Patients with ESRD due to hypertension (n = 214), diabetes (n = 239), other specified causes (n = 181), unknown causes (n = 82) and control subjects drawn from the general population (n = 361). MAIN OUTCOME MEASURES: Participants' history of hypertension. RESULTS: The prevalence of hypertension was 90% in ESRD patients and 27% in controls. Only 6% of patients with hypertensive ESRD had a history of malignant hypertension. Patients with hypertensive ESRD were more likely to have been hospitalized because of hypertension (36%) than were other ESRD patients (18%) or controls (5%). ESRD of any cause was more strongly associated with hypertension of > or = 25 years duration (odds ratio 51.0, compared with normal blood pressure) than it was with hypertension of shorter duration (15-25 years: odds ratio 31.8, 5-15 years: odds ratio 16.0, < 5 years: odds ratio 21.2). Among patients who had both hypertension and ESRD, the diagnosis of 'hypertensive ESRD' was associated independently with a long duration of hypertension, greater severity of hypertension, the absence of diabetes, black race, and limited education. CONCLUSIONS: Hypertension is common among patients with ESRD. The risk of ESRD from any cause increases progressively with the duration of hypertension, and with indicators of severe hypertension. This result supports the hypothesis that nonmalignant hypertension of long duration may cause renal insufficiency. The criteria used to diagnose hypertensive ESRD are consistent with pathophysiologic and epidemiologic evidence.

Adult↗
PubMed1997

Kidney damage in 'benign' essential hypertension.

During the past 12 months additional evidence has emerged from observational studies indicating that high blood pressure is an important independent predictor of incident renal damage, progression of existing renal disease, and morbidity and mortality in patients with renal failure. Several of these studies suggest that elevation of systolic blood pressure is a stronger predictor of risk than a corresponding increase in diastolic blood pressure. Furthermore, the relationship between blood pressure and incident renal disease appears to be positive and continuous throughout the entire spectrum of blood pressure, including in the 'normotensive' range. Recent clinical trial experience in patients with renal insufficiency of diverse etiology supports the beneficial effect of treatment with angiotensin-converting enzyme inhibitors noted in earlier studies confined to patients with type II diabetes. Ongoing trials should help clarify optimal choice of antihypertensive medications and goals for reduction of blood pressure in prevention of renal disease. In the interim, two new guidelines for management of hypertension in patients with existing renal disease provide helpful guidance for the clinician.

Antihypertensive Agents↗
PubMed1997

The emergence of case-control studies in hypertension research: valid or misleading?

Recently published case-control studies have generated considerable controversy. Compared with prospective studies, case-control studies permit investigation of uncommon diseases or outcomes in a more cost and time efficient manner. In addition, multiple possible risk factors can be studied simultaneously. If the assumptions of the study design are met, results of case-control studies are valid. For this reason, the use of this study design has increased markedly. This review summarizes the advantages and disadvantages of this study design and criteria to evaluate the results of such studies.

Calcium Channel Blockers↗
PubMed1997

Exercise and depression in midlife: a prospective study.

OBJECTIVES: This study examined the relationship of self-reported physical activity with subsequent depression and psychiatric distress. METHODS: Physical activity was assessed in medical school and midlife in 973 physicians as part of a prospective observational study. Outcome measures were the incidence of self-reported clinical depression and psychiatric distress on the General Health Questionnaire. RESULTS: The risk of depression was similar for nonexercisers and exercisers. No relationship was observed between physical activity level and subsequent psychiatric distress. CONCLUSIONS: This study found no evidence that exercise reduces risk for depression or psychiatric distress.

Adult↗
PubMed1996

Effect of migration and related environmental changes on serum lipid levels in southwestern Chinese men.

To determine migration-related differences in serum lipid levels and to estimate the contribution of environmental factors to these differences, the authors conducted a cross-sectional study among 1,222 residents of southwestern China in 1988 and 1989: 521 Yi farmers living in a remote rural area, 340 Yi migrants to an urban setting, and 361 Han people living in the same urban setting. Serum total and high density lipoprotein cholesterol and serum triglyceride were measured after a 14-hour fast. Information on age, cigarette smoking, alcohol consumption, and physical activity was obtained by questionnaire. Diet was assessed by use of three 24-hour diet recalls. The Yi farmers had the lowest age-adjusted serum lipid levels among the three groups, white the Yi migrants and their Han counterparts had similar lipid levels. After adjustment for age, body mass index, cigarette smoking, alcohol drinking, and dietary nutrient intake, the difference in serum lipid profile between the Yi migrants and the Yi farmers was substantially reduced. These results indicate that rural-urban migration is associated with higher serum lipid levels. This migration-related difference in serum lipids can be partially explained by changes in lifestyle and dietary nutrient intake. The authors conclude that environmental factors are important determinants of population serum lipid levels in southwestern Chinese.

Adolescent↗
PubMed1996

Blood pressure and end-stage renal disease in men.

BACKGROUND: End-stage renal disease in the United States creates a large burden for both individuals and society as a whole. Efforts to prevent the condition require an understanding of modifiable risk factors. METHODS: We assessed the development of end-stage renal disease through 1990 in 332,544 men, 35 to 57 years of age, who were screened between 1973 and 1975 for entry into the Multiple Risk Factor Intervention Trial (MRFIT). We used data from the national registry for treated end-stage renal disease of the Health Care Financing Administration and from records on death from renal disease from the National Death Index and the Social Security Administration. RESULTS: During an average of 16 years of follow-up, 814 subjects either died of end-stage renal disease or were treated for that condition (15.6 cases per 100,000 person-years of observation). A strong, graded relation between both systolic and diastolic blood pressure and end-stage renal disease was identified, independent of associations between the disease and age, race, income, use of medication for diabetes mellitus, history of myocardial infarction, serum cholesterol concentration, and cigarette smoking. As compared with men with an optimal level of blood pressure (systolic pressure < 120 mm Hg and diastolic pressure < 80 mm Hg), the relative risk of end-stage renal disease for those with stage 4 hypertension (systolic pressure > or = 210 mm Hg or diastolic pressure > or = 120 mm Hg) was 22.1 (P < 0.001). These relations were not due to end-stage renal disease that occurred soon after screening and, in the 12,866 screened men who entered the MRFIT study, were not changed by taking into account the base-line serum creatinine concentration and urinary protein excretion. The estimated risk of end-stage renal disease associated with elevations of systolic pressure was greater than that linked with elevations of diastolic pressure when both variables were considered together. CONCLUSIONS: Elevations of blood pressure are a strong independent risk factor for end-stage renal disease; interventions to prevent the disease need to emphasize the prevention and control of both high-normal and high blood pressure.

Adult↗
PubMed1996

Diabetes mellitus, race, and socioeconomic status. A population-based study.

To identify factors associated with diabetes mellitus and to determine whether racial differences in these factors, especially socioeconomic status, explain the high prevalence of diabetes among African-Americans, we performed a cross-sectional study using a population-based, representative sample from three US communities. The participants comprised 975 white and 418 African-American adults, aged 35 to 54 years. The main outcome variable was the presence of diabetes defined by either self-report or abnormal results on the oral glucose tolerance test (serum glucose level > 10.0 mmol/L (180 mg/dL) 1 hour after 50-g oral glucose dose). Compared to their white counterparts, African-American participants were more overweight, displayed greater central adiposity, and had lower socioeconomic status. Diabetes was over twice as prevalent among African-Americans (10.3%) as compared to whites (4.6%; odds ratio (OR) = 2.38; 95% confidence interval (95% CI): 1.50, 3.75; P = 0.0001). After adjustments for racial differences in age, socioeconomic status, overweight, and central adiposity, African-Americans remained over twice as likely to have diabetes compared to whites (OR = 2.35; 95% CI: 1.49, 3.73; P = 0.0003). The excess prevalence of diabetes in African-Americans was greatest in individuals of low socioeconomic status (OR = 4.09) and least among individuals of high socioeconomic status (OR = 1.90; P < 0.001 for trend). Racial differences in obesity and socioeconomic status do not appear to explain fully the higher prevalence of diabetes among African-Americans. African-American race seems to be a strong, independent risk factor for diabetes, especially among individuals of low socioeconomic status.

Adult↗
PubMed1996

Analgesics and chronic renal disease.

Intake of analgesics has been associated with the presence of chronic renal diseases in a number of studies. Phenacetin was the first drug to be linked with chronic renal disease. Four out of five case-control studies that have examined this issue have also demonstrated an association of acetaminophen use with renal disease. Non-steroidal anti-inflammatory drugs have not been available for a long enough time to evaluate risk associated with their use. Several studies suggest that mixtures of analgesics are most harmful to the Kidney. The National Kidney Foundation recently issued a position paper on analgesics and the kidney that provides guidance to patients and providers.

Analgesics↗
PubMed1996

The role of blood pressure as a risk factor for renal disease: a review of the epidemiologic evidence.

The aim of the paper is to examine the relationship between blood pressure (BP) and renal disease with an overview of observational and experimental investigations, with the emphasis on studies that provide data obtained in unselected population samples. We have found an increasing body of evidence from cross-sectional, case-control, prospective, and experimental studies that indicate BP is an important, independent predictor of both increased relative and attributable risk of renal insufficiency and end-stage renal disease. The relationship between BP and subsequent renal disease appears to be positive and continuous throughout the entire range of BP. Furthermore, the data indicate that elevations in systolic BP (SBP) are stronger predictors of risk compared to corresponding increases in diastolic BP (DBP). Clinical trials experience suggests that reduction in BP decreases the risk of subsequent renal disease. Ongoing trials should help to clarify issues related to choice of antihypertensive therapy and optimal goals for reduction of BP in order to prevent renal disease.

Animals↗
PubMed1995

The contribution of urinary cations to the blood pressure differences associated with migration.

People living in unacculturated societies have a low average blood pressure and little rise in blood pressure with age. In a community-based survey in southwestern China, the authors assessed the contribution of urinary cation excretion to differences in blood pressure between an unacculturated group (Yi farmers) and migrants to an urban environment, as well as urban controls from a different ethnic group (Han). In March 1989, blood pressure and overnight urinary electrolyte levels were measured on 3 consecutive days in 313 Yi farmers, 265 Yi migrants, and 253 urban Han residents, all male. Of the urinary electrolytes, a higher sodium:potassium ratio best explained the higher blood pressure in the migrants. Yi farmers had lower systolic (106.7 mmHg vs. 114.8 mmHg, respectively) and diastolic (66.2 mmHg vs. 71.3 mmHg, respectively) blood pressures than Yi migrants. However, even after adjustment for age, body mass index, alcohol intake, and urinary sodium, potassium, calcium, and magnesium excretion, Yi farmers continued to have lower average blood pressures than Yi migrants. In pooled analyses of all three groups, urinary sodium and calcium were positively related and urinary potassium and magnesium were inversely related to blood pressure. Migration is associated with a higher blood pressure that is only partially explained by higher levels of adiposity and alcohol and sodium intake and lower levels of potassium and magnesium intake.

Adult↗
PubMed1995

Race and end-stage renal disease. Socioeconomic status and access to health care as mediating factors.

OBJECTIVE: To examine whether lower socioeconomic status and limited access to health care explain the racial inequities in the incidence of end-stage renal disease (ESRD), and whether these factors are independently associated with ESRD. METHODS: This case-control study compared 716 patients with ESRD with 361 population controls of the same age, 20 to 64 years old, from Maryland, Virginia, West Virginia, and Washington, DC. Race, indicators of socioeconomic status (household annual income, years of education), and indicators of access to health care (health insurance status, number of missing teeth, usual source of care, use of preventive services) were assessed via a telephone interview. RESULTS: Independent risk factors for ESRD included non-white race (odds ratio for blacks, 5.5; 95% confidence interval, 3.8 to 8.0; odds ratio for other nonwhites, 3.5; 95% confidence interval, 1.2 to 10.0), categories of income (odds ratio gradient, 1.0 to 4.5; 95% confidence interval, 2.6 to 7.8), receipt of Medicaid benefits (odds ratio, 3.5; 95% confidence interval, 1.5 to 8.4), and number of missing teeth (odds ratio gradient, 1.0 to 2.2; 95% confidence interval, 1.2 to 4.1). Adjustment for socioeconomic variables reduced the odds ratio for blacks only partially, from 8.1 to 5.5. The proportions of ESRD incidence that could be attributed to each risk factor were 46% for minority race, 53% for income categories, and 33% for missing teeth. CONCLUSIONS: Low socioeconomic status and limited access to health care were strong risk factors for kidney failure, but they explained only part of the excess of ESRD in blacks. Racial and social factors account for a large part of ESRD incidence. The mechanisms of these associations should be targeted by further research.

Adult↗
PubMed1995

Diagnosis of hypertensive end-stage renal disease: effect of patient's race.

The authors conducted a simulation study to examine whether the race of a patient with end-stage renal disease (ESRD) influences the diagnosis of underlying kidney disease made by the nephrologist. The hypothesis was that ESRD may be more readily ascribed to hypertension in blacks than in whites. Nephrologists practicing in Maryland during 1991 were sent written case histories based on the presentation of seven patients with ESRD. For each case history, the patient's race was randomly assigned to be "black" or "white." The nephrologist's diagnosis of underlying renal disease was recorded as "hypertensive" or "other." Analysis of 197 case histories from 58 physicians (81% of those eligible) was performed using logistic regression. The distribution of underlying causes of ESRD in the case histories was similar to national statistics: hypertensive ESRD, 34%; diabetic ESRD, 30%; glomerulonephritis, 11%; other, 16%; unknown, 10%. Case histories that identified the patient's race as black were more likely (odds ratio = 1.97; 95% confidence interval 1.05-3.68) to result in a diagnosis of hypertensive ESRD than case histories in which the patient's race was said to be white, after adjustment for case history. Analyses that accounted for the physicians' individual tendencies to diagnose hypertensive ESRD yielded similar results. These findings suggest that black ESRD patients may be more likely to be labeled as having hypertensive kidney disease than white ESRD patients with similar clinical histories. Using race as a criterion to establish diagnoses of kidney disease may obscure the interpretation of incidence statistics, affect the management of individual patients, and hinder epidemiologic studies of risk factors for kidney failure. Definition of clear diagnostic criteria for the underlying cause of kidney failure is highly desirable.

Adult↗
PubMed1995

Racial differences in the incidence of gout. The role of hypertension.

OBJECTIVE: To estimate the incidence of and examine risk factors for the development of gout in black and white male physicians. METHODS: Data from 2 cohorts of former medical students, 352 black men in the Meharry Cohort Study and 571 white men in the Johns Hopkins Precursors Study, were analyzed. Cases of gout were identified by self-report. Baseline variables and incident hypertension were examined as risk factors for the development of gout in both cohorts. RESULTS: The incidence of gout was 3.11 and 1.82 per 1,000 person-years in the black men and the white men, respectively (P < 0.05); the cumulative incidence was 10.9% and 5.8%, respectively (P = 0.04). The relative risk (RR) for gout among the black men was 1.69 (95% confidence interval [95% CI] 1.02-2.80). This excess risk persisted after adjustment for baseline systolic blood pressure (adjusted RR = 1.96 [95% CI 1.14-3.38]). Incident hypertension was independently associated with the development of gout in univariate analysis (RR = 3.78 [95% CI 2.18-6.58]); when this variable was included as a time-dependent covariate in a Cox model, the excess risk for gout in black men was reduced and no longer significant (adjusted RR = 1.30 [95% CI 0.77-2.19]). CONCLUSION: The approximately 2-fold excess risk for gout among black men is explained, in part, by a greater risk of incident hypertension.

Adult↗
PubMed1995

Studying the causes of kidney disease in humans: a review of methodologic obstacles and possible solutions.

Until recently, epidemiology has contributed little to the understanding of kidney disease etiology. In the past, the immediate need for therapy eclipsed the longer-term need to develop preventive strategies. As a result, kidney disease epidemiology lacked sufficient institutional and financial support. These difficulties are being progressively (albeit yet incompletely) resolved. Other obstacles pertained to research methods. The need for large cohort studies to investigate a relatively uncommon outcome can be overcome by the use of alternative study designs, such as nonconcurrent prospective studies or case control studies. Unfortunately, other methodologic obstacles remain. These include (1) lack of sensitive markers of early renal insufficiency for use in general populations, (2) variations in access to end-stage renal disease therapy, (3) uncertainty regarding cause-of-death certification in persons with kidney diseases, (4) ambiguous criteria for diagnosing specific renal diseases, (5) lack of independence between risk factor assessments and kidney disease definition, (6) inconsistent risk factor assessments, and (7) inadequate conceptual models for causation of kidney failure. We suggest a global framework, including (1) defining rigorous diagnostic criteria for renal diseases, (2) conducting etiologic studies of "all-cause" end-stage renal disease, (3) systematically collecting data on risk factors for renal injury, and (5) distinguishing between initiators and promoters of renal insufficiency and between proximate and distal risk factors. These suggestions aim to foster a multidisciplinary debate on etiologic research on renal diseases. Identification of modifiable risk factors may provide a basis for effective preventive interventions.

Epidemiologic Methods↗