850 resultados para Population-based studies
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Body fat distribution, particularly centralized obesity, is associated with metabolic risk above and beyond total adiposity. We performed genome-wide association of abdominal adipose depots quantified using computed tomography (CT) to uncover novel loci for body fat distribution among participants of European ancestry. Subcutaneous and visceral fat were quantified in 5,560 women and 4,997 men from 4 population-based studies. Genome-wide genotyping was performed using standard arrays and imputed to ~2.5 million Hapmap SNPs. Each study performed a genome-wide association analysis of subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), VAT adjusted for body mass index, and VAT/SAT ratio (a metric of the propensity to store fat viscerally as compared to subcutaneously) in the overall sample and in women and men separately. A weighted z-score meta-analysis was conducted. For the VAT/SAT ratio, our most significant p-value was rs11118316 at LYPLAL1 gene (p = 3.1 × 10E-09), previously identified in association with waist-hip ratio. For SAT, the most significant SNP was in the FTO gene (p = 5.9 × 10E-08). Given the known gender differences in body fat distribution, we performed sex-specific analyses. Our most significant finding was for VAT in women, rs1659258 near THNSL2 (p = 1.6 × 10-08), but not men (p = 0.75). Validation of this SNP in the GIANT consortium data demonstrated a similar sex-specific pattern, with observed significance in women (p = 0.006) but not men (p = 0.24) for BMI and waist circumference (p = 0.04 [women], p = 0.49 [men]). Finally, we interrogated our data for the 14 recently published loci for body fat distribution (measured by waist-hip ratio adjusted for BMI); associations were observed at 7 of these loci. In contrast, we observed associations at only 7/32 loci previously identified in association with BMI; the majority of overlap was observed with SAT. Genome-wide association for visceral and subcutaneous fat revealed a SNP for VAT in women. More refined phenotypes for body composition and fat distribution can detect new loci not previously uncovered in large-scale GWAS of anthropometric traits.
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OBJECTIVE: Plasma adiponectin is strongly associated with various components of metabolic syndrome, type 2 diabetes and cardiovascular outcomes. Concentrations are highly heritable and differ between men and women. We therefore aimed to investigate the genetics of plasma adiponectin in men and women. METHODS: We combined genome-wide association scans of three population-based studies including 4659 persons. For the replication stage in 13795 subjects, we selected the 20 top signals of the combined analysis, as well as the 10 top signals with p-values less than 1.0 x 10(-4) for each the men- and the women-specific analyses. We further selected 73 SNPs that were consistently associated with metabolic syndrome parameters in previous genome-wide association studies to check for their association with plasma adiponectin. RESULTS: The ADIPOQ locus showed genome-wide significant p-values in the combined (p=4.3 x 10(-24)) as well as in both women- and men-specific analyses (p=8.7 x 10(-17) and p=2.5 x 10(-11), respectively). None of the other 39 top signal SNPs showed evidence for association in the replication analysis. None of 73 SNPs from metabolic syndrome loci exhibited association with plasma adiponectin (p>0.01). CONCLUSIONS: We demonstrated the ADIPOQ gene as the only major gene for plasma adiponectin, which explains 6.7% of the phenotypic variance. We further found that neither this gene nor any of the metabolic syndrome loci explained the sex differences observed for plasma adiponectin. Larger studies are needed to identify more moderate genetic determinants of plasma adiponectin.
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PURPOSE: Subclinical hypothyroidism has been associated with elevated cholesterol and increased risk for atherosclerosis, but data on the risk of coronary heart disease (CHD) are conflicting. We performed a systematic review to determine whether subclinical hypothyroidism is associated with CHD in adults. METHODS: We searched MEDLINE from 1966 to April 2005, and the bibliographies of key articles to identify studies that provided risk estimates for CHD or cardiovascular mortality associated with subclinical hypothyroidism. Two authors independently reviewed each potential study for eligibility, assessed methodologic quality, and extracted the data. RESULTS: We identified 14 observational studies that met eligibility criteria. Subclinical hypothyroidism increased the risk of CHD (summary odds ratio [OR]: 1.65, 95% confidence interval [CI], 1.28-2.12). The summary OR for CHD was 1.81 (CI, 1.38-2.39) in 9 studies adjusted or matched for demographic characteristics, and 2.38 (CI, 1.53-3.69) after pooling the studies that adjusted for most cardiovascular risk factors. Sensitivity analyses including only population-based studies and those with formal outcome adjudication procedures yielded similar results. Subgroup analyses by type of study design showed a similar trend, but lower risk, in the 5 prospective cohort studies (OR 1.42, CI, 0.91-2.21), compared with the case-control and cross-sectional studies (OR 1.72, CI, 1.25-2.38). CONCLUSION: Our systematic review indicates that subclinical hypothyroidism is associated with an increased risk of CHD. Clinical trials are needed to assess whether thyroxine replacement reduces the risk of CHD in subjects with subclinical hypothyroidism.
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Background Area-based measures of socioeconomic position (SEP) suitable for epidemiological research are lacking in Switzerland. The authors developed the Swiss neighbourhood index of SEP (Swiss-SEP). Methods Neighbourhoods of 50 households with overlapping boundaries were defined using Census 2000 and road network data. Median rent per square metre, proportion households headed by a person with primary education or less, proportion headed by a person in manual or unskilled occupation and the mean number of persons per room were analysed in principle component analysis. The authors compared the index with independent income data and examined associations with mortality from 2001 to 2008. Results 1.27 million overlapping neighbourhoods were defined. Education, occupation and housing variables had loadings of 0.578, 0.570 and 0.362, respectively, and median rent had a loading of −0.459. Mean yearly equivalised income of households increased from SFr42 000 to SFr72 000 between deciles of neighbourhoods with lowest and highest SEP. Comparing deciles of neighbourhoods with lowest to highest SEP, the age- and sex-adjusted HR was 1.38 (95% CI 1.36 to 1.41) for all-cause mortality, 1.83 (95% CI 1.71 to 1.95) for lung cancer, 1.48 (95% CI 1.44 to 1.51) for cardiovascular diseases, 2.42 (95% CI 1.94 to 3.01) for traffic accidents, 0.93 (95% CI 0.85 to 1.02) for breast cancer and 0.86 (95% CI 0.78 to 0.95) for suicide. Conclusions Developed using a novel approach to define neighbourhoods, the Swiss-SEP index was strongly associated with household income and some causes of death. It will be useful for clinical- and population-based studies, where individual-level socioeconomic data are often missing, and to investigate the effects on health of the socioeconomic characteristics of a place.
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OBJECTIVE: To assess the seasonality of cardiovascular risk factors (CVRF) in a large set of population-based studies. METHODS: Cross-sectional data from 24 population-based studies from 15 countries, with a total sample size of 237 979 subjects. CVRFs included Body Mass Index (BMI) and waist circumference; systolic (SBP) and diastolic (DBP) blood pressure; total, high (HDL) and low (LDL) density lipoprotein cholesterol; triglycerides and glucose levels. Within each study, all data were adjusted for age, gender and current smoking. For blood pressure, lipids and glucose levels, further adjustments on BMI and drug treatment were performed. RESULTS: In the Northern and Southern Hemispheres, CVRFs levels tended to be higher in winter and lower in summer months. These patterns were observed for most studies. In the Northern Hemisphere, the estimated seasonal variations were 0.26 kg/m(2) for BMI, 0.6 cm for waist circumference, 2.9 mm Hg for SBP, 1.4 mm Hg for DBP, 0.02 mmol/L for triglycerides, 0.10 mmol/L for total cholesterol, 0.01 mmol/L for HDL cholesterol, 0.11 mmol/L for LDL cholesterol, and 0.07 mmol/L for glycaemia. Similar results were obtained when the analysis was restricted to studies collecting fasting blood samples. Similar seasonal variations were found for most CVRFs in the Southern Hemisphere, with the exception of waist circumference, HDL, and LDL cholesterol. CONCLUSIONS: CVRFs show a seasonal pattern characterised by higher levels in winter, and lower levels in summer. This pattern could contribute to the seasonality of CV mortality.
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BACKGROUND AND OBJECTIVES: Neonatal arterial ischemic stroke (NAIS) is associated with considerable lifetime burdens such as cerebral palsy, epilepsy, and cognitive impairment. Prospective epidemiologic studies that include outcome assessments are scarce. This study aimed to provide information on the epidemiology, clinical manifestations, infarct characteristics, associated clinical variables, treatment strategies, and outcomes of NAIS in a prospective, population-based cohort of Swiss children. METHODS: This prospective study evaluated the epidemiology, clinical manifestations, vascular territories, associated clinical variables, and treatment of all full-term neonates diagnosed with NAIS and born in Switzerland between 2000 and 2010. Follow-up was performed 2 years (mean 23.3 months, SD 4.3 months) after birth. RESULTS: One hundred neonates (67 boys) had a diagnosis of NAIS. The NAIS incidence in Switzerland during this time was 13 (95% confidence interval [CI], 11-17) per 100 000 live births. Seizures were the most common symptom (95%). Eighty-one percent had unilateral (80% left-sided) and 19% had bilateral lesions. Risk factors included maternal risk conditions (32%), birth complications (68%), and neonatal comorbidities (54%). Antithrombotic and antiplatelet therapy use was low (17%). No serious side effects were reported. Two years after birth, 39% were diagnosed with cerebral palsy and 31% had delayed mental performance. CONCLUSIONS: NAIS in Switzerland shows a similar incidence as other population-based studies. About one-third of patients developed cerebral palsy or showed delayed mental performance 2 years after birth, and children with normal mental performance may still develop deficits later in life.
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BACKGROUND: Smoking is an important cardiovascular disease risk factor, but the mechanisms linking smoking to blood pressure are poorly understood. METHODS AND RESULTS: Data on 141 317 participants (62 666 never, 40 669 former, 37 982 current smokers) from 23 population-based studies were included in observational and Mendelian randomization meta-analyses of the associations of smoking status and smoking heaviness with systolic and diastolic blood pressure, hypertension, and resting heart rate. For the Mendelian randomization analyses, a genetic variant rs16969968/rs1051730 was used as a proxy for smoking heaviness in current smokers. In observational analyses, current as compared with never smoking was associated with lower systolic blood pressure and diastolic blood pressure and lower hypertension risk, but with higher resting heart rate. In observational analyses among current smokers, 1 cigarette/day higher level of smoking heaviness was associated with higher (0.21 bpm; 95% confidence interval 0.19; 0.24) resting heart rate and slightly higher diastolic blood pressure (0.05 mm Hg; 95% confidence interval 0.02; 0.08) and systolic blood pressure (0.08 mm Hg; 95% confidence interval 0.03; 0.13). However, in Mendelian randomization analyses among current smokers, although each smoking increasing allele of rs16969968/rs1051730 was associated with higher resting heart rate (0.36 bpm/allele; 95% confidence interval 0.18; 0.54), there was no strong association with diastolic blood pressure, systolic blood pressure, or hypertension. This would suggest a 7 bpm higher heart rate in those who smoke 20 cigarettes/day. CONCLUSIONS: This Mendelian randomization meta-analysis supports a causal association of smoking heaviness with higher level of resting heart rate, but not with blood pressure. These findings suggest that part of the cardiovascular risk of smoking may operate through increasing resting heart rate.
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Background: Interest in limb defects has grown after the thalidomide tragedy in the 1960s. As a result, congenital malformation registries, monitoring changes in birthprevalence and defect patterns, have been established in several countries. However, there are only a few true population based studies on birth prevalence of upper limb defects. The burden of hospital care among these children, specifically in terms of the number of admissions and total time spent in hospital, is also unknown. Aims and Methods: This study is based on information gathered from the Finnish Register of Congenital malformations (FRM) and the Finnish Hospital Discharge Register (FHDR). A total of 417 children born between 1993 and 2005 with an upper limb defect were gathered from the FRM. The upper limb defects were classified using the International Federation of Societies for Surgery of the Hand -classification that enables comparison with previous and future studies. Birth and live birth prevalence, sex and side distribution, frequency of associated anomalies as well as the proportion of perinatal and infant deaths according to the different subtypes were calculated. The number of hospital admissions, days spent in hospital, number and type of surgical operations were collected from the FHDR. Special features of two subgroups, radial ray defects (RRD) and constriction band syndrome (CBS), were explored. Results: Upper limb defects were observed in 417 of 753 342 consecutive births and in 392 of 750 461 live births. Birth prevalence was 5.5 per 10 000 births and 5.2 per 10 000 live births. Multiple anomalies or a known syndrome was found in 250 cases (60%). Perinatal mortality was 139 per 1000 births and infant mortality 135 per 1000 live births (overall Finnish perinatal mortality <5 per 1000 births and infant mortality 3.7 per 1000 live births). Altogether, 138 infants had RRD and 120 (87%) of these had either a known syndrome or multiple major anomalies. The proportion of perinatal deaths in RRD group was 29% (40/138) and infant deaths 35% (43/123). Fifty-one children had CBS in upper limbs. Fifteen of these (29%) had other major anomalies associated with constriction rings. The number of hospital admissions per year of children with congenital upper limb defects was 11-fold and the time spent in hospital 13-fold as compared with the general paediatric population. Conclusions: Birth prevalence of congenital upper limb defects was 5.5 per 10 000 births and 5.2 per 10 000 live births. RRD was especially associated with other major anomalies and high mortality. Nearly one third of the children with CBS also had other major anomalies suggesting different aetiologies inside the group. The annual burden of hospital care of children with congenital upper limb defects was at least 11-fold as compared with the general paediatric population.
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Whole blood samples (N = 295) were obtained from different locations in Amazonas and Sucre States, in Venezuela. Malaria was diagnosed by microscopy, OptiMAL™ and polymerase chain reaction (PCR), with Plasmodium vivax, P. falciparum, and P. malariae being detected when possible. We identified 93 infections, 66 of which were caused by P. vivax, 26 by P. falciparum, and 1 was a mixed infection. No infection caused by P. malariae was detected. The sensitivity and specificity of each diagnostic method were high: 95.7 and 97.9% for microscopy, 87.0 and 97.9% for OptiMAL, and 98.0 and 100% for PCR, respectively. Most samples (72.2%) showed more than 5000 parasites/µL blood. The sensitivity of the diagnosis by microscopy and OptiMAL decreased with lower parasitemia. All samples showing disagreement among the methods were reevaluated, but the first result was used for the calculations. Parasites were detected in the 6 false-negative samples by microscopy after the second examination. The mixed infection was only detected by PCR, while the other methods diagnosed it as P. falciparum (microscopy) or P. vivax (OptiMAL) infection. Most of the false results obtained with the OptiMAL strip were related to the P. falciparum-specific band, including 3 species misdiagnoses, which could be related to the test itself or to genetic variation of the Venezuelan strains. The use of the microscopic method for malaria detection is recommended for its low cost but is very difficult to implement in large scale, population-based studies; thus, we report here more efficient methods suitable for this purpose.
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Cystic fibrosis is one of the most common autosomal recessive hereditary diseases in the Caucasian population, with an incidence of 1:2000 to 1:3500 liveborns. More than 1000 mutations have been described with the most common being F508del. It has a prevalence of 23-55% within the Brazilian population. The lack of population-based studies evaluating the incidence of cystic fibrosis in São Paulo State, Brazil, and an analysis concerning the costs of implantation of a screening program motivated the present study. A total of 60,000 dried blood samples from Guthrie cards obtained from April 2005 to January 2006 for neonatal screening at 4 reference centers in São Paulo State were analyzed. The immunoreactive trypsinogen (IRT)/IRT protocol was used with the cut-off value being 70 ng/mL. A total of 532 children (0.9%) showed IRT >70 ng/mL and a 2nd sample was collected from 418 (80.3%) of these patients. Four affected children were detected at two centers, corresponding to an incidence of 1:8403. The average age at diagnosis was 69 days, and 3 of the children already showed severe symptoms of the disease. The rate of false-positive results was 95.2% and the positive predictive value for the test was 8%. The cost of detecting an affected subject was approximately US$8,000.00 when this cystic fibrosis program was added to an existing neonatal screening program. The present study clearly shows the difficulties involved in cystic fibrosis screening using the IRT/IRT protocol, particularly in a population with no long-term tradition of neonatal screening.
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Problématique : Plusieurs expositions résidentielles ont été associées à la prévalence de l’asthme. Toutefois, peu d’études populationnelles ont examiné la relation entre ces facteurs et un asthme mal maîtrisé chez l’enfant. Objectif : Évaluer les facteurs environnementaux résidentiels associés à un asthme mal maîtrisé chez les enfants montréalais âgés de 6 mois à 12 ans. Méthodes : Les données sont tirées d’une enquête transversale menée en 2006 sur la santé respiratoire d’enfants montréalais âgés de 6 mois à 12 ans (n=7980). La maîtrise de l’asthme a été évaluée chez les enfants avec un asthme actif au cours de l’année précédent l’enquête (n=980) selon des critères recommandés par les lignes directrices canadiennes sur l’asthme. Les rapports de prévalence (RP) et les intervalles de confiance (IC) à 95 % caractérisant l’association entre les facteurs environnementaux, incluant la présence d’allergènes, d’irritants, d’humidité et de moisissures, et le risque d’un asthme mal maîtrisé ont été estimés à l’aide de modèles de régression log-binomiale. Les sujets avec une maîtrise acceptable de l’asthme ont été comparés à ceux dont la maladie était mal maîtrisée. Résultats : Des 980 enfants avec un asthme actif au cours de l’année précédant l’enquête, 36 % ont rencontré au moins un des critères des lignes directrices canadiennes suggérant un asthme mal maîtrisé. Les caractéristiques de la population associées à un asthme mal maîtrisé sont : un plus jeune âge, des antécédents d’atopie parentale, une faible scolarisation de la mère, une mère d’origine étrangère et le statut de locataire. Après ajustement pour l’âge de l’enfant, l’atopie parentale et l’exposition à la fumée de tabac au domicile, une intensité de trafic élevée à proximité du domicile (RP, 1,35; IC 95 %, 1,00-1,81) et la localisation au sous-sol de la chambre de l’enfant ou de sa résidence (RP 1,30; IC 95 %, 1,01-1,66) étaient associées à un risque accru d’asthme mal maîtrisé. Conclusions : Une maîtrise sous-optimale de l’asthme semble être associée à l’exposition au trafic routier et à des conditions d’humidité excessive et probablement de moisissures. Cette dernière exposition étant plus fréquente, elle a probablement un plus grand impact en matière de santé publique.
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Résumé: Les anti-infectieux sont parmi les médicaments les plus utilisés pendant la grossesse. Les indications pour l’utilisation de ces médicaments, telles que les infections bactériennes, figurent parmi les facteurs de risque les plus importants pour la prématurité et les enfants nés petits pour l'âge gestationnel («Small-for-gestational-age », SGA). Ces complications de la grossesse peuvent avoir des incidences sur la santé du nouveau né et sur son développement futur. Compte tenu des impacts sur la santé de la mère et de l’enfant, la prise en charge et le traitement efficace de ces infections sont impératifs. Cependant, l'utilisation des anti-infectieux, pour éviter des issues de grossesse défavorables, fait l’objet d’une controverse dans la littérature. Cette controverse est en partie liée à la qualité méthodologique discutable des études disponibles sur le sujet. Les quatre études présentées dans cette thèse ont donc pour objectif d’investiguer l’utilisation des anti-infectieux durant la grossesse ainsi que d’évaluer le risque de prématurité et de SGA après utilisation de ces médicaments en période gestationnelle. Une révision systématique de la littérature sur l’utilisation du métronidazole durant la grossesse est également présentée. Nous avons utilisé, comme source de données le Registre des Grossesses du Québec, une cohorte longitudinale conçue à partir du jumelage de trois bases de données administratives de la province du Québec (RAMQ, Med-Echo et ISQ). Le registre fournit des informations sur les prescriptions, les services pharmaceutiques et médicaux, ainsi que des donnés sur les soins d’hospitalisation de courte durée et démographiques. Les deux premières études présentées dans cette thèse ont eu pour objectif d’évaluer la prévalence, les tendances, les indications et les prédicteurs de l’utilisation des anti-infectieux dans une cohorte, extraite du registre, de 97 680 femmes enceintes. A l’aide d’un devis cas-témoins, les 2 dernières études ont mesuré l’association entre l’utilisation d’anti-infectieux durant les 2 derniers trimestres de grossesse et le risque de prématurité et de SGA, respectivement. Un cas de prématurité a été défini comme un accouchement survenu avant 37 semaines de gestation. Un cas de SGA a été défini comme l’accouchement d’un enfant dont le poids à la naissance se situe sous le 10ème percentile du poids normalisé à la naissance (compte tenu de l’âge gestationnel et du sexe du bébé). Les données ont été recueillies pour les agents systémiques oraux, ainsi que pour les classes et les agents individuels. Nos résultats ont montré que la prévalence de l’utilisation des anti-infectieux durant la grossesse était comparable à celle d’autres études déjà publiées (25%). Nous avons observé une augmentation de l’utilisation des agents plus anciens et ayant des profils d’innocuité connus. Les prédicteurs de l’usage en début de grossesse identifiés sont : avoir eu plus de deux différentes prescriptions (OR ajusté = 3,83, IC 95% : 3,3-4,3), avoir eu un diagnostic d’infection urinaire (OR= 1,50, IC 95% : 1,3-1,8) et un diagnostic d’infection respiratoire (OR= 1,40, IC 95% : 1,2-1,6). L’utilisation des macrolides a été associée à une diminution du risque de prématurité (OR =0,65, IC 95% : 0,50-0,85). En revanche, les femmes ayant été exposées au métronidazole ont vu leur risque augmenté de 80% (OR=1,81, IC 95% : 1,30-2,54). L’utilisation d’azithromycine a été associée à une diminution importante du risque chez les femmes ayant un diagnostic de rupture prématurée des membranes (OR=0,31, IC 95% : 0,10-0,93). Cependant, l'utilisation de sulfaméthoxazole-triméthoprime (SXT) a été significativement associée à une augmentation du risque de SGA (OR= 1,61, IC 95% : 1,16-2,23), tandis que celle des anti-infectieux urinaires a été associée à une diminution du risque (OR= 0,80, 95%CI : 0.65-0.97). Les conclusions de nos travaux suggèrent que l’utilisation des macrolides et des pénicillines diminuent le risque de prématurité et de SGA. Nous devons considérer l'utilisation de différents choix thérapeutiques tels que l’azithromycine, lors de la prise en charge des infections pouvant induire la prématurité et le SGA.
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Introducción: La endocarditis infecciosa es una infección microbiana del endocardio poco estudiada en nuestro país, la cual se asocia con múltiples complicaciones clínicas, y que presenta una mortalidad importante, que no ha disminuido a lo largo del tiempo sin importar los cambios epidemiológicos, de tratamiento y el aumento de la cirugía valvular que se presentan en la actualidad. Metodología: Se realizó la búsqueda de los pacientes adultos con diagnóstico de endocarditis infecciosa entre los años 2002 a 2012 en la Fundación Cardioinfantil para la revisión de los registros médicos y la descripción de las características clínicas, microbiológicas y ecocardiográficas. Resultados: se detectaron 144 pacientes hallando un predominio de la lesión de válvula nativa y el compromiso de válvula aórtica, encontrando como germen más común el S. aureus, sin embargo una tasa de 32.6% de hemocultivos negativos. La mortalidad intrahospitalaria fue de 22.2%. Discusión: los datos hallados en general son semejantes a los descritos en la literatura mundial con excepción de algunas variables discordantes en cuanto a la válvula aórtica mayormente comprometida y factores asociados a la endocarditis tricuspidea. Conclusión: la epidemiología de la endocarditis infecciosa de nuestra serie es muy semejante a la de la literatura actual de los países industrializados, aunque con algunas excepciones, requiriéndose la implementación y profundización del estudio de esta patología a nivel nacional.
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Se realizó un estudio cualitativo exploratorio con estudiantes de carreras de Ciencias de la Salud con el objetivo de comprender las representaciones sociales que tienen acerca de la Medicina Complementaria y Alternativa (MCA) para el cáncer. Se desarrollaron grupos focales y la información obtenida fue analizada a través del Análisis Temático e interpretada con base en la Teoría de las Representaciones Sociales. Se encontraron diversas representaciones sociales asociadas con la definición, los objetivos, los tratamientos, la eficacia, las fuentes de información y el origen de la MCA. En conclusión se evidenció una alta tendencia a la aceptación y a la manifestación de una actitud positiva, aunque ambivalente frente a la MCA, además de un desconocimiento por la diferenciación conceptual entre este tipo de Medicina y la Medicina Popular. La cultura y las creencias sociales predominan en las representaciones sociales que tienen los estudiantes de la MCA para el cáncer, pese a su formación académica.
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The INSIG2 rs7566605 polymorphism was identified for obesity (BMI> or =30 kg/m(2)) in one of the first genome-wide association studies, but replications were inconsistent. We collected statistics from 34 studies (n = 74,345), including general population (GP) studies, population-based studies with subjects selected for conditions related to a better health status ('healthy population', HP), and obesity studies (OB). We tested five hypotheses to explore potential sources of heterogeneity. The meta-analysis of 27 studies on Caucasian adults (n = 66,213) combining the different study designs did not support overall association of the CC-genotype with obesity, yielding an odds ratio (OR) of 1.05 (p-value = 0.27). The I(2) measure of 41% (p-value = 0.015) indicated between-study heterogeneity. Restricting to GP studies resulted in a declined I(2) measure of 11% (p-value = 0.33) and an OR of 1.10 (p-value = 0.015). Regarding the five hypotheses, our data showed (a) some difference between GP and HP studies (p-value = 0.012) and (b) an association in extreme comparisons (BMI> or =32.5, 35.0, 37.5, 40.0 kg/m(2) versus BMI<25 kg/m(2)) yielding ORs of 1.16, 1.18, 1.22, or 1.27 (p-values 0.001 to 0.003), which was also underscored by significantly increased CC-genotype frequencies across BMI categories (10.4% to 12.5%, p-value for trend = 0.0002). We did not find evidence for differential ORs (c) among studies with higher than average obesity prevalence compared to lower, (d) among studies with BMI assessment after the year 2000 compared to those before, or (e) among studies from older populations compared to younger. Analysis of non-Caucasian adults (n = 4889) or children (n = 3243) yielded ORs of 1.01 (p-value = 0.94) or 1.15 (p-value = 0.22), respectively. There was no evidence for overall association of the rs7566605 polymorphism with obesity. Our data suggested an association with extreme degrees of obesity, and consequently heterogeneous effects from different study designs may mask an underlying association when unaccounted for. The importance of study design might be under-recognized in gene discovery and association replication so far.