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- Burgess, S., et al.
(författare)
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Bayesian methods for meta-analysis of causal relationships estimated using genetic instrumental variables
- 2010
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Ingår i: Statistics in medicine. - : Wiley. - 1097-0258 .- 0277-6715. ; 29:12, s. 1298-311
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Tidskriftsartikel (refereegranskat)abstract
- Genetic markers can be used as instrumental variables, in an analogous way to randomization in a clinical trial, to estimate the causal relationship between a phenotype and an outcome variable. Our purpose is to extend the existing methods for such Mendelian randomization studies to the context of multiple genetic markers measured in multiple studies, based on the analysis of individual participant data. First, for a single genetic marker in one study, we show that the usual ratio of coefficients approach can be reformulated as a regression with heterogeneous error in the explanatory variable. This can be implemented using a Bayesian approach, which is next extended to include multiple genetic markers. We then propose a hierarchical model for undertaking a meta-analysis of multiple studies, in which it is not necessary that the same genetic markers are measured in each study. This provides an overall estimate of the causal relationship between the phenotype and the outcome, and an assessment of its heterogeneity across studies. As an example, we estimate the causal relationship of blood concentrations of C-reactive protein on fibrinogen levels using data from 11 studies. These methods provide a flexible framework for efficient estimation of causal relationships derived from multiple studies. Issues discussed include weak instrument bias, analysis of binary outcome data such as disease risk, missing genetic data, and the use of haplotypes.
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| 2. |
- Pukkala, Eero, et al.
(författare)
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Nordic biological specimen banks as basis for studies of cancer causes and control - more than 2 million sample donors, 25 million person years and 100 000 prospective cancers
- 2007
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Ingår i: Acta Oncologica. - : Informa UK Limited. - 1651-226X .- 0284-186X. ; 46:3, s. 286-307
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Tidskriftsartikel (refereegranskat)abstract
- The Nordic countries have a long tradition of large-scale biobanking and comprehensive, population-based health data registries linkable on unique personal identifiers, enabling follow-up studies spanning many decades. Joint Nordic biobank-based studies provide unique opportunities for longitudinal molecular epidemiological research. The purpose of the present paper is to describe the possibilities for such joint studies, by describing some of the major Nordic biobank cohorts with a standardised calculation of the cancer incidence in these cohorts. Altogether two million donors have since 1966 donated more than four million biological samples, stored at -20 degrees C to -135 degrees C, to 17 biobank cohorts in Finland, Iceland, Norway and Sweden. As a result of joint database handling principles, the accuracy of personal identifiers and completeness of follow-up for vital status in all participating biobanks was improved. Thereafter, the cancer incidence was determined using follow-up through the national cancer registries. Biobanks based on random samples of population typically showed slightly lower cancer incidence rates than the general population, presumably due to better participation rates among health-conscious subjects. On the other hand, biobanks including samples for viral screening or clinical testing showed 1.5 to 2.1 fold increased incidence of cancer. This excess was very high immediately after sampling, but for some cancer sites remained elevated for years after clinical sampling. So far, more than 100 000 malignant neoplasms have occurred after sample donation, and the annual increase of the cancer cases in these cohorts is about 10 000. The estimates on the population-representativity of the biobanks will assist in interpretation of generalizability of results of future studies based on these samples, and the systematic tabulations of numbers of cancer cases will serve in study power estimations. The present paper summarizes optimal study designs of biobank-based studies of cancer.
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| 7. |
- Bamia, C, et al.
(författare)
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Dietary patterns among older Europeans: the EPIC-Elderly study
- 2005
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Ingår i: British Journal of Nutrition. - 1475-2662 .- 0007-1145. ; 94:1, s. 100-113
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Tidskriftsartikel (refereegranskat)abstract
- Overall dietary patterns have been associated with health and longevity. We used principal component (PC) and cluster analyses to identify the prevailing dietary patterns of 99 744 participants, aged 60 years or older, living in nine European countries and participating in the European Prospective Investigation into Cancer and Nutrition (EPIC-Elderly cohort) and to examine their socio-demographic and lifestyle correlates. Two PC were identified: PC1 reflects a 'vegetable-based' diet with an emphasis on foods of plant origin, rice, pasta and other grain rather than on margarine, potatoes and non-alcoholic beverages. PC2 indicates a 'sweet- and fat-dominated' diet with a preference for sweets, added fat and dairy products but not meat, alcohol, bread and eggs. PC1 was associated with a younger age, a higher level of education, physical activity, a higher BMI, a lower waist:hip ratio and never and past smoking. PC2 was associated with older age, less education, never having smoked, a lower BMI and waist:hip ratio and lower levels of physical activity. Elderly individuals in southern Europe scored positively on PC1 and about zero on PC2, whereas the elderly in northern Europe scored negatively on PC1 and variably on PC2. The results of cluster analysis were compatible with the indicated dietary patterns. 'Vegetable-based' and a 'sweet- and fat-dominated' diets are prevalent among the elderly across Europe, and there is a north-south gradient regarding their dietary choices. Our study contributes to the identification of groups of elderly who are likely to have different prospects for long-term disease occurrence and survival.
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| 9. |
- Britton, Julie A, et al.
(författare)
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Anthropometric characteristics and non-Hodgkin's lymphoma and multiple myeloma risk in the European Prospective Investigation into Cancer and Nutrition (EPIC).
- 2008
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Ingår i: Haematologica. - : Ferrata Storti Foundation (Haematologica). - 0390-6078 .- 1592-8721. ; 93:11, s. 1666-1677
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:The incidences of non-Hodgkin's lymphoma and multiple myeloma are increasing steadily. It has been hypothesized that this may be due, in part, to the parallel rising prevalence of obesity. It is biologically plausible that anthropometric characteristics can infuence the risk of non-Hodgkin's lymphoma and multiple myeloma.DESIGN AND METHODS:In the context of the European Prospective Investigation into Cancer and Nutrition (EPIC), anthropometric characteristics were assessed in 371,983 cancer-free individuals at baseline. During the 8.5 years of follow-up, 1,219 histologically confirmed incident cases of non-Hodgkin's lymphoma and multiple myeloma occurred in 609 men and 610 women. Gender-specific proportional hazards models were used to estimate relative risks and 95% confidence intervals (95% CI) of development of non-Hodgkin's lymphoma and multiple myeloma in relation to the anthropometric characteristics.RESULTS:Height was associated with overall non-Hodgkin's lymphoma and multiple myeloma in women (RR 1.50, 95% CI 1.14-1.98) for highest versus lowest quartile; p-trend < 0.01) but not in men. Neither obesity (weight and body mass index) nor abdominal fat (waist-to-hip ratio, waist or hip circumference) measures were positively associated with overall non-Hodgkin's lymphoma and multiple myeloma. Relative risks for highest versus lowest body mass index quartile were 1.09 (95% CI 0.85-1.38) and 0.92 (95% CI 0.71-1.19) for men and women, respectively. Women in the upper body mass index quartile were at greater risk of diffuse large B-cell lymphoma (RR 2.18, 95% CI 1.05-4.53) and taller women had an elevated risk of follicular lymphoma (RR 1.25, 95% CI 0.59-2.62). Among men, height and body mass index were non-significantly, positively related to follicular lymphoma. Multiple myeloma risk alone was elevated for taller women (RR 2.34, 95% CI 1.29-4.21) and heavier men (RR 1.77, 95% CI 1.02-3.05).CONCLUSIONS:The EPIC analyses support an association between height and overall non-Hodgkin's lymphoma and multiple myeloma among women and suggest heterogeneous subtype associations. This is one of the first prospective studies focusing on central adiposity and non-Hodgkin's lymphoma subtypes.
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| 10. |
- Capella, Gabriel, et al.
(författare)
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DNA repair polymorphisms and the risk of stomach adenocarcinoma and severe chronic gastritis in the EPIC-EURGAST study
- 2008
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Ingår i: International Journal of Epidemiology. - : Oxford University Press (OUP). - 1464-3685 .- 0300-5771. ; 37:6, s. 1316-1325
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Tidskriftsartikel (refereegranskat)abstract
- Background The contribution of genetic variation in DNA repair genes to gastric cancer (GC) risk remains essentially unknown. The aim of this study was to explore the relative contribution of DNA repair gene polymorphisms to GC risk and severe chronic atrophic gastritis (SCAG). Method A nested case control study within the EPIC cohort was performed including 246 gastric adenocarcinomas and 1175 matched controls. Controls with SCAG (n 91), as defined by low pepsinogen A (PGA) levels, and controls with no SCAG (n 1061) were also compared. Twelve polymorphisms at DNA repair genes (MSH2, MLH1, XRCC1, OGG1 and ERCC2) and TP53 gene were analysed. Antibodies against Helicobacter pylori were measured. Results No association was observed for any of these polymorphisms with stomach cancer risk. However, ERCC2 K751Q polymorphism was associated with an increased risk for non-cardial neoplasm [odds ratio (OR) 1.78; 95 confidence interval (CI) 1.023.12], being ERCC2 K751Q and D312N polymorphisms associated with the diffuse type. ERCC2 D312N (OR 2.0; 95 CI 1.093.65) and K751Q alleles (OR 1.82; 95 CI 1.013.30) and XRCC1 R399Q (OR 1.69; 95 CI 1.022.79) allele were associated with an increased risk for SCAG. Conclusion Our study supports a role of ERCC2 in non-cardial GC but not in cardial cancer. A concordant result was observed for subjects with low PGA levels. XRCC1 allele was associated also with SCAG. This is the first prospective study suggesting that individual variation in DNA repair may be relevant for gastric carcinogenesis, a finding that will require further confirmation validation in larger independent studies.
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