Eliseo Guallar

Serum Selenium Levels and All-Cause, Cancer, and Cardiovascular Mortality Among US Adults

BACKGROUND Selenium, an essential trace element involved in defense against oxidative stress, may prevent cancer and cardiovascular disease. We evaluated the association between selenium levels and all-cause and cause-specific mortality in a representative sample of US adults. METHODS Serum selenium levels were measured in 13,887 adult participants in the Third National Health and Nutrition Examination Survey. Study participants were recruited from 1988 to 1994 and followed up for mortality for up to 12 years. RESULTS The mean serum selenium level was 125.6 ng/mL. The multivariate adjusted hazard ratios comparing the highest (> or = 130.39 ng/mL) with the lowest (< 117.31 ng/mL) serum selenium level tertile were 0.83 (95% confidence interval [CI], 0.72-0.96) for all-cause mortality, 0.69 (95% CI, 0.53-0.90) for cancer mortality, and 0.94 (95% CI, 0.77-1.16) for cardiovascular mortality. However, based on spline regression models, the association between serum selenium levels and all-cause and cancer mortality was nonlinear, with an inverse association at low selenium levels (< 130 ng/mL) and a modest increase in mortality at high selenium levels (> 150 ng/mL). There was no association between serum selenium levels and cardiovascular mortality. CONCLUSIONS In a representative sample of the US population, we found a nonlinear association between serum selenium levels and all-cause and cancer mortality. Increasing serum selenium levels were associated with decreased mortality up to 130 ng/mL. Our study, however, raises the concern that higher serum selenium levels may be associated with increased mortality.

Omega-3 Fatty Acids in Adipose Tissue and Risk of Myocardial Infarction The EURAMIC Study

Omega-3 fatty acids have potential antiatherogenic, antithrombotic, and antiarrhythmic properties, but their role in coronary heart disease remains controversial. To evaluate the association of omega-3 fatty acids in adipose tissue with the risk of myocardial infarction in men, a case-control study was conducted in eight European countries and Israel. Cases (n=639) included patients with a first myocardial infarction admitted to coronary care units within 24 hours from the onset of symptoms. Controls (n=700) were selected to represent the populations originating the cases. Adipose tissue levels of fatty acids were determined by capillary gas chromatography. The mean (+/-SD) proportion of alpha-linolenic acid was 0.77% (+/-0.19) of fatty acids in cases and 0.80% (+/-0.19) of fatty acids in controls (P=0.01). The relative risk for the highest quintile of alpha-linolenic acid compared with the lowest was 0.42 (95% confidence interval [CI] 0.22 to 0.81, P-trend=0.02). After adjusting for classical risk factors, the relative risk for the highest quintile was 0.68 (95% CI 0.31 to 1.49, P-trend=0.38). The mean proportion of docosahexaenoic acid was 0.24% (+/-0.13) of fatty acids in cases and 0.25% (+/-0.13) of fatty acids in controls (P=0. 14), with no evidence of association with risk of myocardial infarction. In this large case-control study we could not detect a protective effect of docosahexaenoic acid on the risk of myocardial infarction. The protective effect of alpha-linolenic acid was attenuated after adjusting for classical risk factors (mainly smoking), but it deserves further research.

DDT (dicophane) and postmenopausal breast cancer in Europe: case-control study.

Abstract Objective: To examine any possible links between exposure to DDE (1,1-dichloro-2,2-bis (p -chlorophenyl)ethylene), the persistent metabolite of the pesticide dicophane (DDT), and breast cancer. Design: Multicentre study of exposure to DDE by measurement of adipose tissue aspirated from the buttocks. Laboratory measurements were conducted in a single laboratory. Additional data on risk factors for breast cancer were obtained by standard questionnaires. Setting: Centres in Germany, the Netherlands, Northern Ireland, Switzerland, and Spain. Subjects: 265 postmenopausal women with breast cancer and 341 controls matched for age and centre. Main outcome measure: Adipose DDE concentrations. Results: Women with breast cancer had adipose DDE concentrations 9.2% lower than control women. No increased risk of breast cancer was found at higher concentrations. The odds ratio of breast cancer, adjusted for age and centre, for the highest versus the lowest fourth of DDE distribution was 0.73 (95% confidence interval 0.44 to 1.21) and decreased to 0.48 (0.25 to 0.95; P for trend=0.02) after adjustment for body mass index, age at first birth, and current alcohol drinking. Adjustment for other risk factors did not materially affect these estimates. Conclusions: The lower DDE concentrations observed among the women with breast cancer may be secondary to disease inception. This study does not support the hypothesis that DDE increases risk of breast cancer in postmenopausal women in Europe. Key messages Organochlorines such as polychlorinated biphenyls and DDT may increase the risk of breast cancer in women DDE concentrations among the women with cancer were lower than among the controls, and there was an inverse risk gradient with higher DDE concentrations which remained significant after adjustment for risk factors for breast cancer These results are clearly incompatible with an increased risk of breast cancer at increased concentrations of DDE, although associations with other organochlorines cannot be excluded

Does Peer Review Predict the Performance of Research Projects in Health Sciences

Peer review is a basic component of the scientific process, but its performance has seldom been evaluated systematically. To determine whether pre-approval characteristics of research projects predicted the performance of projects, we conducted a retrospective cohort study of all 2744 single-centre research projects financed by the Spanish Health Research Fund since 1988 and completed before 1996. Peer review scores of grant applications were significant predictors of performance of funded projects, and the likelihood of production was also higher for projects with a basic research component, longer duration, higher budget or a financed research fellow. Funding agencies should monitor their selection process and assess the performance of funded projects to design future strategies in supporting health sciences research.

Metaanálisis y revisiones sistemáticas en cardiología

Las tecnicas de metaanalisis se han desarrolladofundamentalmente durante los ultimos 20 anos conel objeto de sistematizar la informacion disponiblerespecto a un problema cientifico. Entre las aportacionesde los metaanalisis destacan el desarrollode tecnicas para la realizacion de busquedas sistematicasde la bibliografia, la seleccion de los estudiosoriginales, la extraccion de las medidas deefecto de los estudios y su sintesis en estimadorescombinados. En el presente articulo se discuten lospasos a seguir en la elaboracion de un metaanalisis,con especial enfasis en la seleccion de los estudiosa incluir, la extraccion de la informacion relevantey los metodos estadisticos para combinar losresultados de los estudios originales. Finalmentese presenta una guia para la evaluacion criticade los metaanalisis y de otras tecnicas de sintesis deresultados de investigacion. La aplicacion de lastecnicas de metaanalisis en cardiologia se ilustracon un metaanalisis de los ensayos clinicos aleatorizadosde angioplastia frente a cirugia cardiaca enpacientes con cardiopatia isquemica.