| 1. |
- Burgess, S., et al.
(författare)
-
Bayesian methods for meta-analysis of causal relationships estimated using genetic instrumental variables
- 2010
-
Ingår i: Statistics in medicine. - : Wiley. - 1097-0258 .- 0277-6715. ; 29:12, s. 1298-311
-
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.
|
|
| 2. |
- Chen, Tianhui, et al.
(författare)
-
IGF-I during primiparous pregnancy and maternal risk of breast cancer
- 2010
-
Ingår i: Breast Cancer Research and Treatment. - : Springer Science and Business Media LLC. - 0167-6806 .- 1573-7217. ; 121:1, s. 169-175
-
Tidskriftsartikel (refereegranskat)abstract
- Previously, we reported that insulin-like growth factor (IGF)-I during early pregnancy is positively associated with maternal risk of breast cancer. To further explore this association, we designed a new study limited to women who donated a blood sample during their first pregnancy ending with childbirth. A case-control study was nested within the Northern Sweden Maternity Cohort in which repository since 1975, serum specimens remaining after early pregnancy screening for infectious diseases had been preserved. Study subjects were selected among women who donated a blood sample during the full-term pregnancy that led to the birth of their first child. Two hundred and forty-four women with invasive breast cancer were eligible. Two controls, matching the index case for age and date at blood donation were selected (n = 453). IGF-I was measured in serum samples on an Immulite 2000 analyzer. Conditional logistic regression was used to estimate odds ratios and 95% confidence intervals. A significant positive association of breast cancer with IGF-I was observed, with OR of 1.73 (95% CI: 1.14-2.63) for the top tertile, P < 0.009. Subgroup analyses did not indicate statistical heterogeneity of the association by ages at sampling and diagnosis or by lag time to cancer diagnosis, although somewhat stronger associations with risk were observed in women < or = age 25 at index pregnancy and for cases diagnosed within 15 years of blood donation. The results of the study add further evidence for an adverse effect of elevated IGF-I concentrations during early reproductive life on risk of breast cancer.
|
|
| 3. |
- Chen, Tianhui, et al.
(författare)
-
Maternal hormones during early pregnancy : a cross-sectional study
- 2010
-
Ingår i: Cancer Causes and Control. - : Springer Science and Business Media LLC. - 0957-5243 .- 1573-7225. ; 21:5, s. 719-727
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Little is known about correlates of first-trimester pregnancy hormones as in most studies maternal hormones have been measured later in gestation. We examined the associations of maternal characteristics and child sex with first-trimester maternal concentrations of four hormones implicated in breast cancer: human chorionic gonadotropin (hCG), alpha-fetoprotein (AFP), insulin-like growth factor (IGF)-I, and IGF-II. METHODS: About 338 serum samples donated to the Northern Sweden Maternity Cohort (NSMC), 1975-2001, during the first trimester of uncomplicated pregnancies, were analyzed for the hormones of interest as a part of a case-control study. The associations of maternal characteristics and child sex with hormone concentrations were investigated by correlation, general linear regression, and multivariate regression models. RESULTS: In the first trimester, greater maternal age was inversely correlated with IGF-I and IGF-II. In comparison with women carrying their first child, already parous women had higher IGF-I but lower hCG. Greater maternal weight and smoking were inversely correlated with hCG. No differences in hormone levels by child sex were observed. CONCLUSIONS: Our analyses indicated that potentially modifiable maternal characteristics (maternal weight and smoking) influence first-trimester pregnancy maternal hormone concentrations.
|
|
| 4. |
|
|
| 5. |
- Salzer, Jonatan, 1981-, et al.
(författare)
-
Epstein-Barr virus antibodies and vitamin D in prospective multiple sclerosis biobank sampels
- 2013
-
Ingår i: Multiple Sclerosis Journal. - : Sage Publications. - 1352-4585 .- 1477-0970. ; 19:12, s. 1587-1591
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Increased antibody reactivity against Epstein-Barr Nuclear Antigen-1 (EBNA-1) has been associated with an increased risk for MS, and high levels of 25-Hydroxyvitamin D (25[OH]D) have been associated with a lower risk for MS. Interaction between these two factors has been proposed.Objectives: To examine the association between antibody reactivity against EBNA-1 and five EBNA-1 domains, and the risk for multiple sclerosis (MS), and to examine if these antibodies and 25(OH)D status interact regarding MS risk in prospectively collected blood samples.Methods: Antibody reactivity (as specified above) and 25(OH)D levels were measured using ELISAs in n=192 MS cases and n=384 matched controls. The risk for MS was analysed using matched logistic regression.Results: The risk for MS increased across tertiles of antibody reactivity against EBNA-1, domain EBNA-1402–502, and domain EBNA-1385–420; p trend <0.001. The risk increase was most pronounced for EBNA-1385–420. In young individuals (below median age at sampling, <26.4 years) these associations were stronger, and 25(OH)D levels correlated inversely to antibody reactivity against EBNA-1 and the EBNA-1 domains.Conclusions: We confirm that increased antibody reactivity against EBNA-1 is a risk factor for MS. Our findings in young individuals suggest that 25(OH)D status might influence the immune response towards Epstein-Barr virus, and thereby modulate MS risk.
|
|
| 6. |
- Salzer, Jonatan, 1981-, et al.
(författare)
-
Smoking as a risk factor for multiple sclerosis
- 2013
-
Ingår i: Multiple Sclerosis Journal. - : Sage Publications. - 1352-4585 .- 1477-0970. ; 19:8, s. 1022-1027
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Smoking has been associated with an increased risk for multiple sclerosis, but no studies have measured levels of the nicotine metabolite cotinine in prospectively collected samples to assess exposure.Objective: To investigate the effects of laboratory defined tobacco use on the risk for multiple sclerosis using prospectively collected biobank blood samples.Methods: Levels of cotinine were measured in n=192 cases, and n=384 matched controls, using an immunoassay. The risk for multiple sclerosis was estimated using matched logistic regression.Results: Elevated cotinine levels (≥10 ng/ml) were associated with a significantly increased risk for multiple sclerosis, (odds ratio, OR 1.5, 95% confidence interval, CI 1.0–2.1). This association was only present in young individuals (below median age at blood sampling, <26.4 years), (OR 2.2, 95% CI 1.3–3.8).Conclusions: This study confirms that smoking is a risk factor for multiple sclerosis. It has the advantage of using analyses of cotinine levels in samples that were collected several years before disease onset, thus excluding any risk for recall bias and minimising the risk for reversed causation. Our results also suggest that the smoking related immunological events that contribute to the development of multiple sclerosis occur early in life.
|
|
| 7. |
- Tjonneland, A., et al.
(författare)
-
Linoleic acid, a dietary n-6 polyunsaturated fatty acid, and the aetiology of ulcerative colitis: a nested case-control study within a European prospective cohort study
- 2009
-
Ingår i: Gut. - : BMJ. - 1468-3288 .- 0017-5749. ; 58:12, s. 1606-1611
-
Tidskriftsartikel (refereegranskat)abstract
- Objective: Dietary linoleic acid, an n-6 polyunsaturated fatty acid, is metabolised to arachidonic acid, a component of colonocyte membranes. Metabolites of arachidonic acid have pro-inflammatory properties and are increased in the mucosa of patients with ulcerative colitis. The aim of this investigation was to conduct the first prospective cohort study investigating if a high dietary intake of linoleic acid increases the risk of developing incident ulcerative colitis. Design and setting: Dietary data from food frequency questionnaires were available for 203 193 men and women aged 30-74 years, resident in the UK, Sweden, Denmark, Germany or Italy and participating in a prospective cohort study, the European Prospective Investigation into Cancer and Nutrition (EPIC). These participants were followed up for the diagnosis of ulcerative colitis. Each case was matched with four controls and the risk of disease calculated by quartile of intake of linoleic acid adjusted for gender, age, smoking, total energy intake and centre. Results: A total of 126 participants developed ulcerative colitis (47% women) after a median follow-up of 4.0 years (range, 1.7-11.3 years). The highest quartile of intake of linoleic acid was associated with an increased risk of ulcerative colitis (odds ratio (OR) = 2.49, 95% confidence interval (CI) = 1.23 to 5.07, p = 0.01) with a significant trend across quartiles (OR = 1.32 per quartile increase, 95% CI = 1.04 to 1.66, p = 0.02 for trend). Conclusions: The data support a role for dietary linoleic acid in the aetiology of ulcerative colitis. An estimated 30% of cases could be attributed to having dietary intakes higher than the lowest quartile of linoleic acid intake.
|
|
| 8. |
- Toniolo, Paolo, et al.
(författare)
-
Human chorionic gonadotropin in pregnancy and maternal risk of breast cancer
- 2010
-
Ingår i: Cancer Research. - 0008-5472 .- 1538-7445. ; 70:17, s. 6779-6786
-
Tidskriftsartikel (refereegranskat)abstract
- Full-term pregnancies are associated with long-term reductions in maternal risk of breast cancer, but the biological determinants of the protection are unknown. Experimental observations suggest that human chorionic gonadotropin (hCG), a major hormone of pregnancy, could play a role in this association. A case-control study (242 cases and 450 controls) nested within the Northern Sweden Maternity Cohort included women who had donated a blood sample during the first trimester of a first full-term pregnancy. Total hCG was determined on Immulite 2000 analyzer. Odds ratios (OR) and 95% confidence intervals (CI) were estimated through conditional logistic regression. Maternal breast cancer risk decreased with increasing hCG (upper tertile OR, 0.67; CI, 0.46-0.99), especially for pregnancies before age 25 (upper tertile OR, 0.41; CI, 0.21-0.80). The association diverged according to age at diagnosis: risk was reduced after age 40 (upper tertile OR, 0.60; CI, 0.39-0.91) and seemed to increase before age 40 (upper tertile OR, 1.78; CI, 0.72-4.38). Risk was reduced among those diagnosed 10 years or longer after blood draw (upper tertile OR, 0.60; CI, 0.40-0.90), but not so among those diagnosed within 10 years (upper tertile OR, 4.33; CI, 0.86-21.7). These observations suggest that the association between pregnancy hCG and subsequent maternal risk of breast cancer is modified by age at diagnosis. Although the hormone seems to be a determinant of the reduced risk around or after age 50, it might not confer protection against, or it could even increase the risk of, cancers diagnosed in the years immediately following pregnancy.
|
|
| 9. |
- Aleksandrova, Krasimira, et al.
(författare)
-
Metabolic syndrome and risks of colon and rectal cancer : the European prospective investigation into cancer and nutrition study.
- 2011
-
Ingår i: Cancer prevention research (Philadelphia, Pa.). - 1940-6215. ; 4:11, s. 1873-83
-
Tidskriftsartikel (refereegranskat)abstract
- Metabolic syndrome (MetS) is purportedly related to risk of developing colorectal cancer; however, the association of MetS, as defined according to recent international criteria, and colorectal cancer has not been yet evaluated. In particular, it remains unclear to what extent the MetS components individually account for such an association. We addressed these issues in a nested case-control study that included 1,093 incident cases matched (1:1) to controls by using incidence density sampling. Conditional logistic regression was used to estimate relative risks (RR) and 95% CIs. MetS was defined according to the criteria of the National Cholesterol Education Program/Adult Treatment Panel III (NCEP/ATPIII), the International Diabetes Federation (IDF), and the 2009 harmonized definition. Among individual components, abdominal obesity (RR = 1.51; 95% CI: 1.16-1.96) was associated with colon cancer, whereas abnormal glucose metabolism was associated with both colon (RR = 2.05; 95% CI: 1.57-2.68) and rectal cancer (RR = 2.07; 95% CI: 1.45-2.96). MetS, as defined by each of the definitions, was similarly associated with colon cancer (e.g., RR = 1.91; 95% CI: 1.47-2.42 for MetS by NCEP/ATPIII), whereas MetS by NCEP/ATPIII, but not IDF or harmonized definition, was associated with rectal cancer (RR = 1.45; 95% CI: 1.02-2.06). Overall, these associations were stronger in women than in men. However, the association between MetS and colorectal cancer was accounted for by abdominal obesity and abnormal glucose metabolism such that MetS did not provide risk information beyond these components (likelihood ratio test P = 0.10 for MetS by NCEP/ATPIII). These data suggest that simple assessment of abnormal glucose metabolism and/or abdominal obesity to identify individuals at colorectal cancer risk may have higher clinical utility than applying more complex MetS definitions. Cancer Prev Res; 4(11); 1873-83. ©2011 AACR.
|
|
| 10. |
- Andersson, Jonas, 1977-, et al.
(författare)
-
Effects of heavy endurance physical exercise on inflammatory markers in non-athletes
- 2010
-
Ingår i: Atherosclerosis. - : Elsevier BV. - 0021-9150 .- 1879-1484. ; 209:2, s. 601-605
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: Physical activity has beneficial effects on cardiovascular disease but the mechanisms are still somewhat unclear. One possible pathway may be through the anti-inflammatory effects attributed to regular physical activity. Our primary aim was to study the effects of endurance physical exercise on C-reactive protein (CRP), Interleukin-6 (IL-6), Tumor Necrosis Factor-alpha (TNFalpha) during the acute and recovery phases. Secondarily, we studied the impact of diet on these inflammatory markers.METHODS: Twenty men, aged 18-55 years, participated in a 14 days cross-country skiing tour. They traveled 12-30km per day corresponding to about 10h of heavy physical activity. The participants were randomized to a diet with either 30 or 40% of energy derived from fat. Inflammatory variables were analysed at week 0, after 1 and 2 weeks and during the recovery phase at week 6 and 8.RESULTS: CRP and TNFalpha increased significantly during the two weeks of exercise (1.4-5.0mg/l, p=0.00 and 6.8-8.4pg/ml, p=0.00). CRP levels were significantly lower during recovery (median 0.7mg/l) compared to baseline (median 1.4mg/l) and did not correlate to metabolic variables. There were no significant changes in IL-6 levels during the study period. For dietary groups significant CRP changes were observed only in the high fat group during recovery.CONCLUSIONS: CRP and TNFalpha increased significantly but reacted differently during heavy physical activity while there seemed to be no significant changes in IL-6. No significant differences regarding inflammatory variables were found between the dietary groups.
|
|
