Biomedical subjects

Eliseo Guallar

Publications and source records attributed to Eliseo Guallar.

31 records · Page 2Linked to original sources

PubMed2005

Metals in urine and peripheral arterial disease.

Exposure to metals may promote atherosclerosis. Blood cadmium and lead were associated with peripheral arterial disease (PAD) in the 1999-2000 National Health and Nutrition Examination Survey (NHANES). In the present study we evaluated the association between urinary levels of cadmium, lead, barium, cobalt, cesium, molybdenum, antimony, thallium, and tungsten with PAD in a cross-sectional analysis of 790 participants > or =40 years of age in NHANES 1999-2000. PAD was defined as a blood pressure ankle brachial index < 0.9 in at least one leg. Metals were measured in casual (spot) urine specimens by inductively coupled plasma-mass spectrometry. After multivariable adjustment, subjects with PAD had 36% higher levels of cadmium in urine and 49% higher levels of tungsten compared with noncases. The adjusted odds ratio for PAD comparing the 75th to the 25th percentile of the cadmium distribution was 3.05 [95% confidence interval (CI), 0.97 to 9.58]; that for tungsten was 2.25 (95% CI, 0.97 to 5.24). PAD risk increased sharply at low levels of antimony and remained elevated beyond 0.1 microg/L. PAD was not associated with other metals. In conclusion, urinary cadmium, tungsten, and possibly antimony were associated with PAD in a representative sample of the U.S. population. For cadmium, these results strengthen previous findings using blood cadmium as a biomarker, and they support its role in atherosclerosis. For tungsten and antimony, these results need to be interpreted cautiously in the context of an exploratory analysis but deserve further study. Other metals in urine were not associated with PAD at the levels found in the general population.

Adult↗

PubMed2004

Meta-analysis: high-dosage vitamin E supplementation may increase all-cause mortality.

BACKGROUND: Experimental models and observational studies suggest that vitamin E supplementation may prevent cardiovascular disease and cancer. However, several trials of high-dosage vitamin E supplementation showed non-statistically significant increases in total mortality. PURPOSE: To perform a meta-analysis of the dose-response relationship between vitamin E supplementation and total mortality by using data from randomized, controlled trials. PATIENTS: 135,967 participants in 19 clinical trials. Of these trials, 9 tested vitamin E alone and 10 tested vitamin E combined with other vitamins or minerals. The dosages of vitamin E ranged from 16.5 to 2000 IU/d (median, 400 IU/d). DATA SOURCES: PubMed search from 1966 through August 2004, complemented by a search of the Cochrane Clinical Trials Database and review of citations of published reviews and meta-analyses. No language restrictions were applied. DATA EXTRACTION: 3 investigators independently abstracted study reports. The investigators of the original publications were contacted if required information was not available. DATA SYNTHESIS: 9 of 11 trials testing high-dosage vitamin E (> or =400 IU/d) showed increased risk (risk difference > 0) for all-cause mortality in comparisons of vitamin E versus control. The pooled all-cause mortality risk difference in high-dosage vitamin E trials was 39 per 10,000 persons (95% CI, 3 to 74 per 10,000 persons; P = 0.035). For low-dosage vitamin E trials, the risk difference was -16 per 10,000 persons (CI, -41 to 10 per 10,000 persons; P > 0.2). A dose-response analysis showed a statistically significant relationship between vitamin E dosage and all-cause mortality, with increased risk of dosages greater than 150 IU/d. LIMITATIONS: High-dosage (> or =400 IU/d) trials were often small and were performed in patients with chronic diseases. The generalizability of the findings to healthy adults is uncertain. Precise estimation of the threshold at which risk increases is difficult. CONCLUSION: High-dosage (> or =400 IU/d) vitamin E supplements may increase all-cause mortality and should be avoided.

Adult↗

PubMed2004

Lead, cadmium, smoking, and increased risk of peripheral arterial disease.

BACKGROUND: Lead and cadmium exposure may promote atherosclerosis, although the cardiovascular effects of chronic low-dose exposure are largely unknown. The objective of the present study was to evaluate the association between blood levels of lead and cadmium and peripheral arterial disease. METHODS AND RESULTS: We analyzed data from 2125 participants who were > or =40 years of age in the 1999 to 2000 National Health and Nutrition Examination Survey (NHANES). Peripheral arterial disease was defined as an ankle brachial index <0.9 in at least 1 leg. Lead and cadmium levels were measured by atomic absorption spectrometry. After adjustment for demographic and cardiovascular risk factors, the ORs of peripheral arterial disease comparing quartiles 2 to 4 of lead with the lowest quartile were 1.63 (95% CI, 0.51 to 5.15), 1.92 (95% CI, 0.62 to 9.47), and 2.88 (95% CI, 0.87 to 9.47), respectively (P for trend=0.02). The corresponding ORs for cadmium were 1.07 (95% CI, 0.44 to 2.60), 1.30 (95% CI, 0.69 to 2.44), and 2.82 (95% CI, 1.36 to 5.85), respectively (P for trend=0.01). The OR of peripheral arterial disease for current smokers compared with never smokers was 4.13. Adjustment for lead reduced this OR to 3.38, and adjustment for cadmium reduced it to 1.84. CONCLUSIONS: Blood lead and cadmium, at levels well below current safety standards, were associated with an increased prevalence of peripheral arterial disease in the general US population. Cadmium may partially mediate the effect of smoking on peripheral arterial disease.

Adult↗

PubMed2004

Preoperative acute normovolemic hemodilution: a meta-analysis.

BACKGROUND: Acute normovolemic hemodilution (ANH) involves withdrawal of whole blood with concurrent infusion of fluids to maintain normovolemia. The aim of this study was to quantify the efficacy and safety of preoperative ANH with a systematic review and meta-analysis. STUDY DESIGN AND METHODS: Randomized controlled trials were identified through MEDLINE (1966-2002) and the Cochrane Controlled Trials Database and with hand searching of journals. All trials of preoperative ANH reporting on allogeneic transfusion, bleeding, or adverse outcomes were included. Paired reviewers independently abstracted data. Outcomes were pooled using random-effects models. RESULTS: A total of 42 trials compared hemodilution to usual care or to another blood conservation method. The risk of allogeneic transfusion was similar among patients receiving ANH and those receiving usual care (relative risk [RR], 0.96; 95% CI, 0.90-1.01), or another blood conservation method (RR, 1.11; 95% CI, 0.96-1.28). Hemodiluted patients, however, were transfused from 1 to 2 fewer units of allogeneic blood. They had less total bleeding than patients receiving usual care (91 mL; 95% CI, 25-158 mL), although more intraoperative bleeding. Only one-third of studies reported on adverse events. CONCLUSIONS: The literature supports only modest benefits from preoperative ANH. The safety of the procedure is unproven. Widespread adoption of ANH cannot be encouraged.

Blood Loss, Surgical↗

PubMed2004

Serum ferritin and risk of the metabolic syndrome in U.S. adults.

OBJECTIVE: We examined the relationship among iron stores, the metabolic syndrome, and insulin resistance. RESEARCH DESIGN AND METHODS: We conducted a cross-sectional study of 6,044 adults >20 years of age who participated in the Third National Health and Nutrition Examination Survey. Metabolic syndrome was defined as the presence of at least three of the following: elevated blood pressure, low HDL cholesterol, elevated serum triglycerides, elevated plasma glucose, and abdominal obesity. Insulin resistance was estimated using homeostasis model assessment (for insulin resistance), fasting insulin, and triglyceride-to-HDL cholesterol ratio. RESULTS: After excluding individuals with likely hemochromatosis, mean serum ferritin values in premenopausal women, postmenopausal women, and men were 33.6, 93.4, and 139.9 microg/l, respectively. Metabolic syndrome was more common in those with the highest compared with the lowest levels of serum ferritin in premenopausal women (14.9 vs. 6.4%, P = 0.002), postmenopausal women (47.5 vs. 28.2%, P < 0.001), and men (27.3 vs. 13.8%, P < 0.001). Insulin resistance also increased across quartiles of serum ferritin for men and postmenopausal women and persisted after adjustment for age, race/ethnicity, C-reactive protein, smoking, alcohol intake, and BMI. CONCLUSIONS: Elevated iron stores were positively associated with the prevalence of the metabolic syndrome and with insulin resistance.

Adult↗

PubMed2003

Systolic blood pressure, diastolic blood pressure, and pulse pressure: an evaluation of their joint effect on mortality.

BACKGROUND: The relative importance of blood pressure components (systolic blood pressure, diastolic blood pressure, and pulse pressure) on cardiovascular risk is currently being debated. Many studies, however, are limited by inadequate statistical methods to separate these effects. OBJECTIVE: To evaluate the joint effect of blood pressure components on all-cause and cardiovascular mortality by using nonparametric and change point models. DESIGN: Prospective cohort study. SETTING: 15-year mortality follow-up of participants in the Second National Health and Nutrition Examination Survey. PARTICIPANTS: 7830 white and African-American men and women 30 to 74 years of age, apparently free of cardiovascular disease at baseline. MEASUREMENTS: Baseline blood pressure, corrected for measurement error. RESULTS: Of the 1588 patients who died, 582 died of cardiovascular disease. Systolic blood pressure was linearly related to all-cause and cardiovascular mortality in younger and elderly participants. The association of diastolic blood pressure with all-cause and cardiovascular mortality was hockey stick-shaped (flat then increasing) in younger participants and J-shaped in elderly participants. Increased pulse pressure was associated with increased risk, decreased risk, or no change in risk depending on age and systolic and diastolic blood pressure. CONCLUSIONS: On the basis of these and previous data, the evidence for a monotonic association of systolic blood pressure with all-cause and cardiovascular mortality is compelling, but a J-shaped association for diastolic blood pressure may develop at older age. The complexity of the association of pulse pressure with mortality discourages its use for prognostic or therapeutic decisions.

Age Factors↗

PubMed2003

Transition models for change-point estimation in logistic regression.

Although a wide variety of change-point models are available for continuous outcomes, few models are available for dichotomous outcomes. This paper introduces transition methods for logistic regression models in which the dose-response relationship follows two different straight lines, which may intersect or may present a jump at an unknown change-point. In these models, the logit includes a differentiable transition function that provides parametric control of the sharpness of the transition at the change-point, allowing for abrupt changes or more gradual transitions between the two different linear trends, as well as for estimation of the location of the change-point. Linear-linear logistic models are particular cases of the proposed transition models. We present a modified iteratively reweighted least squares algorithm to estimate model parameters, and we provide inference procedures including a test for the existence of the change-point. These transition models are explored in a simulation study, and they are used to evaluate the existence of a change-point in the association between plasma glucose after an oral glucose tolerance test and mortality using data from the Mortality Follow-up of the Second National Health and Nutrition Examination Survey.

Adult↗

PubMed2003

Outpatient prescriptions for atypical antipsychotics for African Americans, Hispanics, and whites in the United States.

BACKGROUND: New antipsychotic medications introduced during the past decade-clozapine (1990), risperidone (1994), olanzapine (1996), and quetiapine fumarate (1997)-offer a decrease in serious adverse effects compared with traditional antipsychotic medications, but at up to 10 times the cost. We examined whether ethnic minorities achieve access to these new advanced treatments. METHODS: Using national data on physician office and hospital outpatient department visits from the National Ambulatory Medical Care Survey and National Hospital Ambulatory Medical Care Survey from 1992 through 2000, we selected all patient visits at which an antipsychotic medication (atypical or traditional) was prescribed or continued and the patient was aged between 18 and 69 years. We performed a series of cross-sectional logistic regression analyses to determine the association of ethnic group and receipt of an atypical antipsychotic prescription over time, adjusted for potential confounders such as age, diagnosis, and health insurance type. RESULTS: Antipsychotic medication was prescribed or continued in 5032 visits; 33% of overall visits involved an atypical antipsychotic prescription. During 1992 to 1994, the adjusted relative odds of receipt of an atypical antipsychotic prescription for African Americans was 0.50 (95% confidence interval [CI], 0.26-0.96) and for Hispanics was 0.43 (95% CI, 0.16-1.18) compared with whites. During 1995 to 1997, the odds of receipt of a prescription for atypical antipsychotics increased for African Americans (odds ratio [OR], 0.69; 95% CI, 0.54-0.85) and for Hispanics (OR, 0.84; 95% CI, 0.65-1.07) compared with whites; and during 1998 to 2000, the relative odds continued to increase for African Americans (OR, 0.88; 95% CI, 0.78-0.97) and for Hispanics (OR, 1.05; 95% CI, 0.92-1.16) compared with whites. For visits specified for psychotic disorders, receipt of atypical antipsychotics was still lower for African Americans by 1998 to 2000 (adjusted OR, 0.74; 95% CI, 0.61-0.89) compared with whites, while for Hispanics the relative odds was equivalent (adjusted OR, 1.05; 95% CI, 0.87-1.19). CONCLUSION: Early gaps between ethnic groups in receipt of atypical antipsychotic prescriptions decreased throughout the 1990s but persisted for African Americans with psychotic disorders.

Adolescent↗

PubMed2002

Mercury, fish oils, and the risk of myocardial infarction.

BACKGROUND: It has been suggested that mercury, a highly reactive heavy metal with no known physiologic activity, increases the risk of cardiovascular disease. Because fish intake is a major source of exposure to mercury, the mercury content of fish may counteract the beneficial effects of its n-3 fatty acids. METHODS: In a case-control study conducted in eight European countries and Israel, we evaluated the joint association of mercury levels in toenail clippings and docosahexaenoic acid (C22:6n-3, or DHA) levels in adipose tissue with the risk of a first myocardial infarction among men. The patients were 684 men with a first diagnosis of myocardial infarction. The controls were 724 men selected to be representative of the same populations. RESULTS: The average toenail mercury level in controls was 0.25 microg per gram. After adjustment for the DHA level and coronary risk factors, the mercury levels in the patients were 15 percent higher than those in controls (95 percent confidence interval, 5 to 25 percent). The risk-factor-adjusted odds ratio for myocardial infarction associated with the highest as compared with the lowest quintile of mercury was 2.16 (95 percent confidence interval, 1.09 to 4.29; P for trend=0.006). After adjustment for the mercury level, the DHA level was inversely associated with the risk of myocardial infarction (odds ratio for the highest vs. the lowest quintile, 0.59; 95 percent confidence interval, 0.30 to 1.19; P for trend=0.02). CONCLUSIONS: The toenail mercury level was directly associated with the risk of myocardial infarction, and the adipose-tissue DHA level was inversely associated with the risk. High mercury content may diminish the cardioprotective effect of fish intake.

Adipose Tissue↗

PubMed2002

The effect of magnesium supplementation on blood pressure: a meta-analysis of randomized clinical trials.

BACKGROUND: An increased intake of magnesium might lower blood pressure (BP), yet evidence from clinical trials is inconsistent, perhaps as a result of small sample size or heterogeneity in study design. METHODS: We performed a meta-analysis of randomized trials that tested the effects of magnesium supplementation on BP. Twenty trials meeting the inclusion criteria were identified. Random effects models and meta-regression methods were used to pool study results and to determine the dose-response relationship of magnesium to BP. RESULTS: The 20 studies included 14 of hypertensive and 6 of normotensive persons totaling 1220 participants. The doses of magnesium ranged from 10 to 40 mmol/day (median, 15.4 mmol/day). Magnesium supplementation resulted in only a small overall reduction in BP. The pooled net estimates of BP change (95% confidence interval [CI]) were -0.6 (-2.2 to 1.0) mm Hg for systolic BP and -0.8 (-1.9 to 0.4) mm Hg for diastolic BP. However, there was an apparent dose-dependent effect of magnesium, with reductions of 4.3 mm Hg systolic BP (95% CI 6.3 to 2.2; P < .001) and of 2.3 mm Hg diastolic BP (95% CI 4.9 to 0.0; P = .09) for each 10 mmol/day increase in magnesium dose. CONCLUSIONS: Our meta-analysis detected dose-dependent BP reductions from magnesium supplementation. However, adequately powered trials with sufficiently high doses of magnesium supplements need to be performed to confirm this relationship.

Adult↗

PubMed2002

Utility of whole blood hemostatometry using the clot signature analyzer for assessment of hemostasis in cardiac surgery.

BACKGROUND: A hemostatic monitor capable of rapid, accurate detection of clinical coagulopathy within the operating room could improve management of bleeding after cardiopulmonary bypass (CPB). The Clot Signature Analyzer is a hemostatometer that measures global hemostasis in whole blood. The authors hypothesized that point-of-care hemostatometry could detect a clinical coagulopathic state in cardiac surgical patients. METHODS: Fifty-seven adult patients scheduled for a variety of elective cardiac surgical procedures were studied. Anesthesia, CPB, heparin anticoagulation, protamine reversal, and transfusion for post-CPB bleeding were all managed by standardized protocol. Clinical coagulopathy was defined by the need for platelet or fresh frozen plasma transfusion. The Clot Signature Analyzer collagen-induced thrombus formation (CITF) assay measured platelet-mediated hemostasis in vitro. The activated clotting time, platelet count, prothrombin time, activated partial thromboplastin time, and fibrinogen concentration were also measured. RESULTS: The postprotamine CITF was greater in patients who required hemostatic transfusion than in those who did not (17.6 +/- 8.0 min vs. 10.5 +/- 5.7 min, respectively; P < 0.01). Postprotamine CITF values were highly correlated with platelet and fresh frozen plasma transfusion (Spearman r = 0.50, P < 0.001 and r = 0.40, P < 0.005, respectively). Receiver operator characteristic curves showed a highly significant relation between the postprotamine CITF and intraoperative platelet and fresh frozen plasma transfusion (area under the curve, 0.78-0.81, P < 0.005) with 60-80% sensitivity, specificity, positive and negative predictive values at cutoffs of 12-14 min. Logistic regression demonstrated that the CITF was independently predictive of post-CPB hemostatic transfusion, but standard hemostatic assays were not. CONCLUSIONS: The Clot Signature Analyzer CITF detects a clinical coagulopathic state after CPB and is independently predictive of the need for hemostatic transfusion. Hemostatometry has potential utility for monitoring hemostasis in cardiac surgery.

Algorithms↗

PubMed2002

Receipt of preventive medical services at psychiatric visits by patients with severe mental illness.

The authors used data from the National Ambulatory Medical Care Survey from 1992 to 1999 on 3,198 office visits to explore the extent to which psychiatrists provide clinical preventive medical services to patients with severe mental illness. Preventive services were provided during 11 percent of the visits. A multivariate analysis showed that preventive services were more likely to have been provided for patients with a chronic medical condition, for patients who were also seen by a nurse or other health provider during the visit, in rural areas, and during longer visits. Preventive services were less likely to have been provided during visits to health maintenance organizations and visits that took place later in the study period.

Adolescent↗

PubMedDate not supplied

Meta-analysis of randomized educational and behavioral interventions in type 2 diabetes.

PURPOSE: This meta-analysis was conducted to assess the effect of educational and behavioral interventions on body weight and glycemic control in type 2 diabetes. METHODS: Studies selected for analysis were published randomized controlled trials that evaluated educational and behavioral interventions (no drug interventions) in type 2 diabetes (sample size > or = 10). These criteria were applied to searches of electronic databases and relevant bibliographies. Data were independently abstracted by 2 reviewers and adjudicated by consensus. RESULTS: Of the 63 articles that met the inclusion criteria, 18 provided enough information for pooled estimates of glycohemoglobin (total Ghb, HbA1, or HbA1C). These 18 studies yielded 2720 participants (sample sizes of 18 to 749). Interventions ranged from 1 to 19 months; follow-up ranged from 1 to 26 months. Glycohemoglobin was reduced by a mean of 0.43%. When results were stratified by quality score, glycohemoglobin was -0.50% and -0.38% for studies with high and low quality scores, respectively. When weighting studies by sample size, fasting blood glucose was reduced by 24 mg/dL and weight by 3 lbs. CONCLUSIONS: Previous educational and behavioral interventions in type 2 diabetes have produced modest improvements in glycemic control. Future research should refine such interventions and improve methodology.

Blood Glucose↗