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1.  Job Strain as a Risk Factor for Type 2 Diabetes: A Pooled Analysis of 124,808 Men and Women 
Diabetes Care  2014;37(8):2268-2275.
OBJECTIVE
The status of psychosocial stress at work as a risk factor for type 2 diabetes is unclear because existing evidence is based on small studies and is subject to confounding by lifestyle factors, such as obesity and physical inactivity. This collaborative study examined whether stress at work, defined as “job strain,” is associated with incident type 2 diabetes independent of lifestyle factors.
RESEARCH DESIGN AND METHODS
We extracted individual-level data for 124,808 diabetes-free adults from 13 European cohort studies participating in the IPD-Work Consortium. We measured job strain with baseline questionnaires. Incident type 2 diabetes at follow-up was ascertained using national health registers, clinical screening, and self-reports. We analyzed data for each study using Cox regression and pooled the study-specific estimates in fixed-effect meta-analyses.
RESULTS
There were 3,703 cases of incident diabetes during a mean follow-up of 10.3 years. After adjustment for age, sex, and socioeconomic status (SES), the hazard ratio (HR) for job strain compared with no job strain was 1.15 (95% CI 1.06–1.25) with no difference between men and women (1.19 [1.06–1.34] and 1.13 [1.00–1.28], respectively). In stratified analyses, job strain was associated with an increased risk of diabetes among those with healthy and unhealthy lifestyle habits. In a multivariable model adjusted for age, sex, SES, and lifestyle habits, the HR was 1.11 (1.00–1.23).
CONCLUSIONS
Findings from a large pan-European dataset suggest that job strain is a risk factor for type 2 diabetes in men and women independent of lifestyle factors.
doi:10.2337/dc13-2936
PMCID: PMC4113178  PMID: 25061139
2.  Identity-by-descent mapping in a Scandinavian multiple sclerosis cohort 
In an attempt to map chromosomal regions carrying rare gene variants contributing to the risk of multiple sclerosis (MS), we identified segments shared identical-by-descent (IBD) using the software BEAGLE 4.0's refined IBD analysis. IBD mapping aims at identifying segments inherited from a common ancestor and shared more frequently in case–case pairs. A total of 2106 MS patients of Nordic origin and 624 matched controls were genotyped on Illumina Human Quad 660 chip and an additional 1352 ethnically matched controls typed on Illumina HumanHap 550 and Illumina 1M were added. The quality control left a total of 441 731 markers for the analysis. After identification of segments shared by descent and significance testing, a filter function for markers with low IBD sharing was applied. Four regions on chromosomes 5, 9, 14 and 19 were found to be significantly associated with the risk for MS. However, all markers but for one were located telomerically, including the very distal markers. For methodological reasons, such segments have a low sharing of IBD signals and are prone to be false positives. One marker on chromosome 19 reached genome-wide significance and was not one of the distal markers. This marker was located within the GNA11 gene, which contains no previous association with MS. We conclude that IBD mapping is not sufficiently powered to identify MS risk loci even in ethnically relatively homogenous populations, or that alternatively rare variants are not adequately present.
doi:10.1038/ejhg.2014.155
PMCID: PMC4402631  PMID: 25159868
3.  Postmenopausal hormone therapy and the risk of rheumatoid arthritis: results from the Swedish EIRA population-based case-control study 
European Journal of Epidemiology  2015;30(5):449-457.
To study the association between postmenopausal hormone therapy (PMH) use and the risk of rheumatoid arthritis (RA) stratifying the cases by the presence/absence of antibodies against citrullinated peptides (ACPA). A subset of the Epidemiological Investigation of RA (EIRA), a population-based case-control study, comprising postmenopausal women aged 50–70 living in Sweden, between 2006 and 2011 was analysed (523 cases and 1057 controls). All participants answered an extensive questionnaire, including questions regarding PMH use and potential confounders (education, smoking, BMI, oral contraceptives, reproductive factors). We calculated odds ratios (OR) of developing ACPA-positive/-negative RA, with 95 % confidence intervals (CI) and adjusted for age, residential area and smoking. Current users of PMH had a decreased risk of ACPA-positive RA compared with never users (OR 0.6, 95 % CI 0.3–0.9). The decreased risk was observed mainly in the age-group 50–59 years (OR 0.3, 95 % CI 0.1–0.8) but not in the age-group 60–70 years (OR 0.8, 95 % CI 0.4–1.4). Among current users of a combined therapy (estrogen plus progestogens) an OR of 0.3 (95 % CI 0.1–0.7) of ACPA-positive RA was observed, while no significant association was found among women who used estrogen only (OR 0.8, 95 % CI 0.5–1.6). No association between PMH use and ACPA-negative RA was found. PMH use might reduce the risk of ACPA-positive RA in post-menopausal women over 50 years of age, but not of ACPA-negative RA. The negative influence of this treatment on the risk of other chronic conditions cannot be overlooked.
doi:10.1007/s10654-015-0004-y
PMCID: PMC4457806  PMID: 25762170
Rheumatoid arthritis; Postmenopausal hormone therapy; Antibodies to citrullinated peptides (ACPA); Etiology; Epidemiology
4.  Identification of anticitrullinated protein antibody reactivities in a subset of anti-CCP-negative rheumatoid arthritis: association with cigarette smoking and HLA-DRB1 ‘shared epitope’ alleles 
Annals of the Rheumatic Diseases  2013;74(3):579-586.
Introduction
A hallmark of rheumatoid arthritis (RA) is the development of autoantibodies targeting proteins that contain citrulline. Anticitrullinated protein antibodies (ACPAs) are currently detected by the commercial cyclic citrullinated peptide (CCP) assay, which uses a mix of cyclised citrullinated peptides as an artificial mimic of the true antigen(s). To increase the sensitivity of ACPA detection and dissect ACPA specificities, we developed a multiplex assay that profiles ACPAs by measuring their reactivity to the citrullinated peptides and proteins derived from RA joint tissue.
Methods
We created a bead-based, citrullinated antigen array to profile ACPAs. This custom array contains 16 citrullinated peptides and proteins detected in RA synovial tissues. We used the array to profile ACPAs in sera from a cohort of patients with RA and other non-inflammatory arthritides, as well as sera from an independent cohort of RA patients for whom data were available on carriage of HLA-DRB1 ‘shared epitope’ (SE) alleles and history of cigarette smoking.
Results
Our multiplex assay showed that at least 10% of RA patients who tested negative in the commercial CCP assay possessed ACPAs. Carriage of HLA-DRB1 SE alleles and a history of cigarette smoking were associated with an increase in ACPA reactivity—in anti-CCP+ RA and in a subset of anti-CCP− RA.
Conclusions
Our multiplex assay can identify ACPA-positive RA patients missed by the commercial CCP assay, thus enabling greater diagnostic sensitivity. Further, our findings suggest that cigarette smoking and possession of HLA-DRB1 SE alleles contribute to the development of ACPAs in anti-CCP− RA.
doi:10.1136/annrheumdis-2013-203915
PMCID: PMC4345988  PMID: 24297382
Rheumatoid Arthritis; Autoantibodies; Smoking
5.  A genome-wide association study of anorexia nervosa 
Boraska, Vesna | Franklin, Christopher S | Floyd, James AB | Thornton, Laura M | Huckins, Laura M | Southam, Lorraine | Rayner, N William | Tachmazidou, Ioanna | Klump, Kelly L | Treasure, Janet | Lewis, Cathryn M | Schmidt, Ulrike | Tozzi, Federica | Kiezebrink, Kirsty | Hebebrand, Johannes | Gorwood, Philip | Adan, Roger AH | Kas, Martien JH | Favaro, Angela | Santonastaso, Paolo | Fernández-Aranda, Fernando | Gratacos, Monica | Rybakowski, Filip | Dmitrzak-Weglarz, Monika | Kaprio, Jaakko | Keski-Rahkonen, Anna | Raevuori, Anu | Van Furth, Eric F | Landt, Margarita CT Slof-Op t | Hudson, James I | Reichborn-Kjennerud, Ted | Knudsen, Gun Peggy S | Monteleone, Palmiero | Kaplan, Allan S | Karwautz, Andreas | Hakonarson, Hakon | Berrettini, Wade H | Guo, Yiran | Li, Dong | Schork, Nicholas J. | Komaki, Gen | Ando, Tetsuya | Inoko, Hidetoshi | Esko, Tõnu | Fischer, Krista | Männik, Katrin | Metspalu, Andres | Baker, Jessica H | Cone, Roger D | Dackor, Jennifer | DeSocio, Janiece E | Hilliard, Christopher E | O'Toole, Julie K | Pantel, Jacques | Szatkiewicz, Jin P | Taico, Chrysecolla | Zerwas, Stephanie | Trace, Sara E | Davis, Oliver SP | Helder, Sietske | Bühren, Katharina | Burghardt, Roland | de Zwaan, Martina | Egberts, Karin | Ehrlich, Stefan | Herpertz-Dahlmann, Beate | Herzog, Wolfgang | Imgart, Hartmut | Scherag, André | Scherag, Susann | Zipfel, Stephan | Boni, Claudette | Ramoz, Nicolas | Versini, Audrey | Brandys, Marek K | Danner, Unna N | de Kovel, Carolien | Hendriks, Judith | Koeleman, Bobby PC | Ophoff, Roel A | Strengman, Eric | van Elburg, Annemarie A | Bruson, Alice | Clementi, Maurizio | Degortes, Daniela | Forzan, Monica | Tenconi, Elena | Docampo, Elisa | Escaramís, Geòrgia | Jiménez-Murcia, Susana | Lissowska, Jolanta | Rajewski, Andrzej | Szeszenia-Dabrowska, Neonila | Slopien, Agnieszka | Hauser, Joanna | Karhunen, Leila | Meulenbelt, Ingrid | Slagboom, P Eline | Tortorella, Alfonso | Maj, Mario | Dedoussis, George | Dikeos, Dimitris | Gonidakis, Fragiskos | Tziouvas, Konstantinos | Tsitsika, Artemis | Papezova, Hana | Slachtova, Lenka | Martaskova, Debora | Kennedy, James L. | Levitan, Robert D. | Yilmaz, Zeynep | Huemer, Julia | Koubek, Doris | Merl, Elisabeth | Wagner, Gudrun | Lichtenstein, Paul | Breen, Gerome | Cohen-Woods, Sarah | Farmer, Anne | McGuffin, Peter | Cichon, Sven | Giegling, Ina | Herms, Stefan | Rujescu, Dan | Schreiber, Stefan | Wichmann, H-Erich | Dina, Christian | Sladek, Rob | Gambaro, Giovanni | Soranzo, Nicole | Julia, Antonio | Marsal, Sara | Rabionet, Raquel | Gaborieau, Valerie | Dick, Danielle M | Palotie, Aarno | Ripatti, Samuli | Widén, Elisabeth | Andreassen, Ole A | Espeseth, Thomas | Lundervold, Astri | Reinvang, Ivar | Steen, Vidar M | Le Hellard, Stephanie | Mattingsdal, Morten | Ntalla, Ioanna | Bencko, Vladimir | Foretova, Lenka | Janout, Vladimir | Navratilova, Marie | Gallinger, Steven | Pinto, Dalila | Scherer, Stephen | Aschauer, Harald | Carlberg, Laura | Schosser, Alexandra | Alfredsson, Lars | Ding, Bo | Klareskog, Lars | Padyukov, Leonid | Finan, Chris | Kalsi, Gursharan | Roberts, Marion | Logan, Darren W | Peltonen, Leena | Ritchie, Graham RS | Barrett, Jeffrey C | Estivill, Xavier | Hinney, Anke | Sullivan, Patrick F | Collier, David A | Zeggini, Eleftheria | Bulik, Cynthia M
Molecular psychiatry  2014;19(10):1085-1094.
Anorexia nervosa (AN) is a complex and heritable eating disorder characterized by dangerously low body weight. Neither candidate gene studies nor an initial genome wide association study (GWAS) have yielded significant and replicated results. We performed a GWAS in 2,907 cases with AN from 14 countries (15 sites) and 14,860 ancestrally matched controls as part of the Genetic Consortium for AN (GCAN) and the Wellcome Trust Case Control Consortium 3 (WTCCC3). Individual association analyses were conducted in each stratum and meta-analyzed across all 15 discovery datasets. Seventy-six (72 independent) SNPs were taken forward for in silico (two datasets) or de novo (13 datasets) replication genotyping in 2,677 independent AN cases and 8,629 European ancestry controls along with 458 AN cases and 421 controls from Japan. The final global meta-analysis across discovery and replication datasets comprised 5,551 AN cases and 21,080 controls. AN subtype analyses (1,606 AN restricting; 1,445 AN binge-purge) were performed. No findings reached genome-wide significance. Two intronic variants were suggestively associated: rs9839776 (P=3.01×10-7) in SOX2OT and rs17030795 (P=5.84×10-6) in PPP3CA. Two additional signals were specific to Europeans: rs1523921 (P=5.76×10-6) between CUL3 and FAM124B and rs1886797 (P=8.05×10-6) near SPATA13. Comparing discovery to replication results, 76% of the effects were in the same direction, an observation highly unlikely to be due to chance (P=4×10-6), strongly suggesting that true findings exist but that our sample, the largest yet reported, was underpowered for their detection. The accrual of large genotyped AN case-control samples should be an immediate priority for the field.
doi:10.1038/mp.2013.187
PMCID: PMC4325090  PMID: 24514567
anorexia nervosa; eating disorders; GWAS; genome-wide association study; body mass index; metabolic
6.  Long working hours, socioeconomic status, and the risk of incident type 2 diabetes: a meta-analysis of published and unpublished data from 222 120 individuals 
Summary
Background
Working long hours might have adverse health effects, but whether this is true for all socioeconomic status groups is unclear. In this meta-analysis stratified by socioeconomic status, we investigated the role of long working hours as a risk factor for type 2 diabetes.
Methods
We identified four published studies through a systematic literature search of PubMed and Embase up to April 30, 2014. Study inclusion criteria were English-language publication; prospective design (cohort study); investigation of the effect of working hours or overtime work; incident diabetes as an outcome; and relative risks, odds ratios, or hazard ratios (HRs) with 95% CIs, or sufficient information to calculate these estimates. Additionally, we used unpublished individual-level data from 19 cohort studies from the Individual-Participant-Data Meta-analysis in Working-Populations Consortium and international open-access data archives. Effect estimates from published and unpublished data from 222 120 men and women from the USA, Europe, Japan, and Australia were pooled with random-effects meta-analysis.
Findings
During 1·7 million person-years at risk, 4963 individuals developed diabetes (incidence 29 per 10 000 person-years). The minimally adjusted summary risk ratio for long (≥55 h per week) compared with standard working hours (35–40 h) was 1·07 (95% CI 0·89–1·27, difference in incidence three cases per 10 000 person-years) with significant heterogeneity in study-specific estimates (I2=53%, p=0·0016). In an analysis stratified by socioeconomic status, the association between long working hours and diabetes was evident in the low socioeconomic status group (risk ratio 1·29, 95% CI 1·06–1·57, difference in incidence 13 per 10 000 person-years, I2=0%, p=0·4662), but was null in the high socioeconomic status group (1·00, 95% CI 0·80–1·25, incidence difference zero per 10 000 person-years, I2=15%, p=0·2464). The association in the low socioeconomic status group was robust to adjustment for age, sex, obesity, and physical activity, and remained after exclusion of shift workers.
Interpretation
In this meta-analysis, the link between longer working hours and type 2 diabetes was apparent only in individuals in the low socioeconomic status groups.
Funding
Medical Research Council, European Union New and Emerging Risks in Occupational Safety and Health research programme, Finnish Work Environment Fund, Swedish Research Council for Working Life and Social Research, German Social Accident Insurance, Danish National Research Centre for the Working Environment, Academy of Finland, Ministry of Social Affairs and Employment (Netherlands), Economic and Social Research Council, US National Institutes of Health, and British Heart Foundation.
doi:10.1016/S2213-8587(14)70178-0
PMCID: PMC4286814  PMID: 25262544
7.  Does a healthy lifestyle behaviour influence the prognosis of low back pain among men and women in a general population? A population-based cohort study 
BMJ Open  2014;4(12):e005713.
Objectives
To study the influence of healthy lifestyle behaviour on the prognosis of occasional low back pain among men and women in a general population.
Design
Cohort study with a 4-year follow-up.
Settings
General population in Stockholm County, Sweden.
Participants
The study sample comprised 3938 men and 5056 women aged 18–84 from the Stockholm Public Health Cohort reporting occasional low back pain in the baseline questionnaire 2006.
Measures
Lifestyle factors and potential confounders were assessed at baseline. The lifestyle factors smoking habits, alcohol consumption, leisure physical activity and consumption of fruit and vegetables were dichotomised using recommendations for a health-enhancing lifestyle and combined to form the exposure variable ‘healthy lifestyle behaviour’. The exposure was categorised into five levels according to the number of healthy lifestyle factors met. The follow-up questionnaire in 2010 gave information about the outcome, long duration troublesome low back pain. Crude and adjusted binomial regression models were applied to estimate the association between the exposure and the outcome analysing men and women separately.
Results
The risk of developing long duration troublesome low back pain among women with occasional low back pain decreased with increasing healthy lifestyle behaviour (trend test: p=0.006). 21% (28/131) among women with no healthy lifestyle factor (reference) experienced the outcome compared to 9% (36/420) among women with all four factors. Compared to the reference group, the risk was reduced by 35% (RR 0.65, 95% CI 0.44 to 0.96) for women with one healthy lifestyle factor and 52% (RR 0.48, 95% CI 0.31 to 0.77) for women with all four healthy lifestyle factors. There were no clear associations found among men.
Conclusions
Healthy lifestyle behaviour seems to decrease the risk of developing long duration troublesome low back pain among women with occasional low back pain and may be recommended to improve the prognosis.
doi:10.1136/bmjopen-2014-005713
PMCID: PMC4281558  PMID: 25550292
8.  Genome-wide association study meta-analysis identifies seven new rheumatoid arthritis risk loci 
Nature genetics  2010;42(6):508-514.
To identify novel genetic risk factors for rheumatoid arthritis (RA), we conducted a genome-wide association study (GWAS) meta-analysis of 5,539 autoantibody positive RA cases and 20,169 controls of European descent, followed by replication in an independent set of 6,768 RA cases and 8,806 controls. Of 34 SNPs selected for replication, 7 novel RA risk alleles were identified at genome-wide significance (P<5×10−8) in analysis of all 41,282 samples. The associated SNPs are near genes of known immune function, including IL6ST, SPRED2, RBPJ, CCR6, IRF5, and PXK. We also refined the risk alleles at two established RA risk loci (IL2RA and CCL21) and confirmed the association at AFF3. These new associations bring the total number of confirmed RA risk loci to 31 among individuals of European ancestry. An additional 11 SNPs replicated at P<0.05, many of which are validated autoimmune risk alleles, suggesting that most represent bona fide RA risk alleles.
doi:10.1038/ng.582
PMCID: PMC4243840  PMID: 20453842
9.  Interaction between passive smoking and two HLA genes with regard to multiple sclerosis risk 
Background: The recently described interaction between smoking, human leukocyte antigen (HLA) DRB1*15 and absence of HLA-A*02 with regard to multiple sclerosis (MS) risk shows that the risk conveyed by smoking differs depending on genetic background. We aimed to investigate whether a similar interaction exists between passive smoking and HLA genotype.
Methods: We used one case-control study with incident cases of MS (736 cases, 1195 controls) and one with prevalent cases (575 cases, 373 controls). Never-smokers with different genotypes and passive smoking status were compared with regard to occurrence of MS, by calculating odds ratios (ORs) with 95% confidence intervals (CIs). The potential interaction between different genotypes and passive smoking was evaluated by calculating the attributable proportion (AP) due to interaction.
Results: An interaction was observed between passive smoking and carriage of HLA-DRB1*15 (AP 0.3, 95% CI 0.02–0.5 in the incident study, and AP 0.4, 95% CI 0.1–0.7 in the prevalent study), as well as between passive smoking and absence of HLA-A*02. Compared with non-smokers without any of these two genetic risk factors, non-exposed subjects with the two risk genotypes displayed an OR of 4.5 (95% CI 3.3–6.1) whereas the same genotype for subjects exposed to passive smoking rendered an OR of 7.7 (95% CI 5.5–10.8).
Conclusions: The risk of developing MS associated with different HLA genotypes may be influenced by exposure to passive smoking. The finding supports our hypothesis that priming of the immune response in the lungs may subsequently lead to MS in people with a genetic susceptibility to the disease.
doi:10.1093/ije/dyu195
PMCID: PMC4276064  PMID: 25324153
Multiple sclerosis; smoking; passive smoking; HLA genotype; gene-environment interaction; case-control study; immunology
11.  Non-HLA genes PTPN22, CDK6 and PADI4 are associated with specific autoantibodies in HLA-defined subgroups of rheumatoid arthritis 
Introduction
Genetic susceptibility to complex diseases has been intensively studied during the last decade, yet only signals with small effect have been found leaving open the possibility that subgroups within complex traits show stronger association signals. In rheumatoid arthritis (RA), autoantibody production serves as a helpful discriminator in genetic studies and today anti-citrullinated cyclic peptide (anti-CCP) antibody positivity is employed for diagnosis of disease. The HLA-DRB1 locus is known as the most important genetic contributor for the risk of RA, but is not sufficient to drive autoimmunity and additional genetic and environmental factors are involved. Hence, we addressed the association of previously discovered RA loci with disease-specific autoantibody responses in RA patients stratified by HLA-DRB1*04.
Methods
We investigated 2178 patients from three RA cohorts from Sweden and Spain for 41 genetic variants and four autoantibodies, including the generic anti-CCP as well as specific responses towards citrullinated peptides from vimentin, alpha-enolase and type II collagen.
Results
Our data demonstrated different genetic associations of autoantibody-positive disease subgroups in relation to the presence of DRB1*04. Two specific subgroups of autoantibody-positive RA were identified. The SNP in PTPN22 was associated with presence of anti-citrullinated enolase peptide antibodies in carriers of HLA-DRB1*04 (Cochran-Mantel-Haenszel test P = 0.0001, Pcorrected <0.05), whereas SNPs in CDK6 and PADI4 were associated with anti-CCP status in DRB1*04 negative patients (Cochran-Mantel-Haenszel test P = 0.0004, Pcorrected <0.05 for both markers). Additionally we see allelic correlation with autoantibody titers for PTPN22 SNP rs2476601 and anti-citrullinated enolase peptide antibodies in carriers of HLA-DRB1*04 (Mann Whitney test P = 0.02) and between CDK6 SNP rs42041 and anti-CCP in non-carriers of HLA-DRB1*04 (Mann Whitney test P = 0.02).
Conclusion
These data point to alternative pathways for disease development in clinically similar RA subgroups and suggest an approach for study of genetic complexity of disease with strong contribution of HLA.
Electronic supplementary material
The online version of this article (doi:10.1186/s13075-014-0414-3) contains supplementary material, which is available to authorized users.
doi:10.1186/s13075-014-0414-3
PMCID: PMC4292996  PMID: 25138370
12.  Parity and the risk of developing rheumatoid arthritis: results from the Swedish EIRA study 
Annals of the rheumatic diseases  2013;73(4):752-755.
Objective
To study the impact of parity history on the risk of ACPA- (antibodies to citrullinated peptides antigens) positive/-negative rheumatoid arthritis (RA), in different age-groups.
Method
Data from a population-based case-control study of female incident RA cases were analysed (2035 cases, 2911 controls, aged 18-70). Parity history was assessed through questionnaire. Parous women were compared with nulliparous, by calculating odds ratios (OR) with 95% confidence interval (CI).
Results
Parity was associated with an increased risk of ACPA-negative RA in the age-group 18-44 (OR=2.1, 95% CI 1.4-3.2), but not in the age-group 45-70 (OR=0.9, 95% CI 0.7-1.3). Among young women, an increased risk of ACPA-negative RA was found in those with delivery during the year of symptom onset (OR=2.6, 95% CI 1.4-4.8) and at young age at first birth (<23) (OR=2.5, 95% CI 1.5-4.1).Parity and the postpartum period were not associated with ACPA-positive RA, but older age at first birth was weakly associated with a decreased risk.
Conclusions
The increased risk of ACPA-negative RA in parous women of reproductive age seemed to be conferred to an increased postpartum risk and to young age at first birth. Further research is needed to explore the biological mechanisms behind our findings.
doi:10.1136/annrheumdis-2013-203567
PMCID: PMC4086877  PMID: 23887288
Rheumatoid arthritis; Parity; Postpartum period; Antibodies to citrullinated peptides (ACPA); Epidemiology
13.  Ambient air pollution exposures and risk of rheumatoid arthritis in the Nurses’ Health Study 
Arthritis care & research  2013;65(7):1190-1196.
Objective
Environmental factors may play a role in the development of rheumatoid arthritis (RA), and we have previously observed increased RA risk among women living closer to major roads (a source of air pollution). We examined whether long-term exposures to specific air pollutants were associated with RA risk among women in the Nurses’ Health Study.
Methods
The Nurses’ Health Study (NHS) is a large cohort of U.S. female nurses followed prospectively every two years since 1976. We studied 111,425 NHS participants with information on air pollution exposures as well as data concerning other lifestyle and behavioral exposures and disease outcomes. Outdoor levels of different size fractions of particulate matter (PM10 and PM2.5) and gaseous pollutants (SO2 and NO2) were predicted for all available residential addresses using monitoring data from the USEPA. We examined the association of time-varying exposures, 6 and 10 years before each questionnaire cycle, and cumulative average exposure with the risks of RA, seronegative (rheumatoid factor [RF] and anti–citrullinated peptide antibodies [ACPA]) RA, and seropositive RA.
Results
Over the 3,019,424 years of follow-up, 858 incident RA cases were validated by medical record review by two board-certified rheumatologists. Overall, we found no evidence of increased risks of RA, seronegative or seropositive RA, with exposure to the different pollutants, and little evidence of effect modification by socioeconomic status or smoking status, geographic region, or calendar period.
Conclusion
In this group of socioeconomically-advantaged middle-aged and elderly women, adult exposures to air pollution were not associated with an increased RA risk.
doi:10.1002/acr.21975
PMCID: PMC3659202  PMID: 23401426
14.  Association of Environmental and Genetic Factors and Gene-Environment Interactions with Risk of Developing Rheumatoid Arthritis 
Arthritis care & research  2013;65(7):1147-1156.
Background
We developed RA risk models based on validated environmental factors (E), genetic risk scores (GRS), and gene-environment interactions (GEI) to identify factors that can improve accuracy and reclassification.
Methods
Models including E, GRS, GEI were developed among 317 Caucasian seropositive RA cases and 551 controls from Nurses’ Health Studies (NHS) and validated in 987 Caucasian ACPA positive cases and 958 controls from the Swedish Epidemiologic Investigation of RA (EIRA), stratified by gender. Primary analyses included age, smoking, alcohol, parity, weighted GRS using 31 non-HLA alleles, 8 HLA-DRB1 alleles and HLA X smoking interaction. Expanded models included reproductive, geographic, and occupational factors, and additional GEI terms. Hierarchical models were compared for discriminative accuracy using AUC and reclassification using Integrated Discrimination Improvement (IDI) and continuous Net Reclassification Index.
Results
Mean (SD) age of RA diagnosis was 57 in NHS and 50 in EIRA. Primary models produced an AUC of 0.716 in NHS, 0.728 in EIRA women and 0.756 in EIRA men. Expanded models produced improvements in discrimination with AUCs of 0.738 in NHS, 0.728 in EIRA women and 0.769 in EIRA men. Models including G or G + GEI improved reclassification over E models; the full E+G+GEI model provided the optimal predictive ability by IDI analyses.
Conclusions
We have developed comprehensive RA risk models incorporating epidemiologic and genetic factors and gene-environment interactions that have improved discriminative accuracy for RA. Further work developing and assessing highly specific prediction models in prospective cohorts is still needed to inform primary RA prevention trials.
doi:10.1002/acr.22005
PMCID: PMC3740546  PMID: 23495093
15.  AMBIENT AIR POLLUTION EXPOSURES AND RISK OF RHEUMATOID ARTHRITIS: RESULTS FROM THE SWEDISH EIRA CASE-CONTROL STUDY 
Annals of the rheumatic diseases  2012;72(6):888-894.
Objective
Environmental factors may play a role in the development of rheumatoid arthritis (RA). We examined whether long-term exposures to air pollution were associated with risk of RA in the Swedish Epidemiological Investigation of Rheumatoid Arthritis (EIRA) Study.
Methods
We studied 1,497 incident RA cases and 2,536 controls. Local levels of particulate matter (PM10) and gaseous pollutants (SO2 and NO2,) from traffic and home heating were predicted for all residential addresses. We examined the association of an interquartile range increase (2μg/m3 for PM10, 8μg/m3 for SO2, and 9μg/m3 for NO2) in each pollutant at different time points prior to symptom onset and average exposure with the risk of all RA and the risk of the rheumatoid factor (RF) and anti-citrullinated protein antibody (ACPA) RA phenotypes.
Results
There was no evidence of an increased risk of RA with PM10. Total RA risks were modestly elevated for the gaseous pollutants, but were not statistically significant after adjustment for smoking and education (odds ratio (OR)=1.18 [95%confidence interval (CI): 0.97–1.43] and OR=1.09 [95%CI: 0.99–1.19] for SO2 and NO2 in the 10th year before onset). Stronger elevated risks were observed for individuals with less than a university education and with the ACPA- RA phenotype.
Conclusion
No consistent overall associations between air pollution in the Stockholm area and risk for RA were observed. However, there was a suggestion of increased risks of RA incidence with increases in NO2 from local traffic and SO2 from home heating sources with stronger associations for the ACPA- phenotype.
doi:10.1136/annrheumdis-2012-201587
PMCID: PMC3654032  PMID: 22833374
air pollution; rheumatoid arthritis; traffic pollution; home heating pollution
16.  Analysis of immune-related loci identifies 48 new susceptibility variants for multiple sclerosis 
Beecham, Ashley H | Patsopoulos, Nikolaos A | Xifara, Dionysia K | Davis, Mary F | Kemppinen, Anu | Cotsapas, Chris | Shahi, Tejas S | Spencer, Chris | Booth, David | Goris, An | Oturai, Annette | Saarela, Janna | Fontaine, Bertrand | Hemmer, Bernhard | Martin, Claes | Zipp, Frauke | D’alfonso, Sandra | Martinelli-Boneschi, Filippo | Taylor, Bruce | Harbo, Hanne F | Kockum, Ingrid | Hillert, Jan | Olsson, Tomas | Ban, Maria | Oksenberg, Jorge R | Hintzen, Rogier | Barcellos, Lisa F | Agliardi, Cristina | Alfredsson, Lars | Alizadeh, Mehdi | Anderson, Carl | Andrews, Robert | Søndergaard, Helle Bach | Baker, Amie | Band, Gavin | Baranzini, Sergio E | Barizzone, Nadia | Barrett, Jeffrey | Bellenguez, Céline | Bergamaschi, Laura | Bernardinelli, Luisa | Berthele, Achim | Biberacher, Viola | Binder, Thomas M C | Blackburn, Hannah | Bomfim, Izaura L | Brambilla, Paola | Broadley, Simon | Brochet, Bruno | Brundin, Lou | Buck, Dorothea | Butzkueven, Helmut | Caillier, Stacy J | Camu, William | Carpentier, Wassila | Cavalla, Paola | Celius, Elisabeth G | Coman, Irène | Comi, Giancarlo | Corrado, Lucia | Cosemans, Leentje | Cournu-Rebeix, Isabelle | Cree, Bruce A C | Cusi, Daniele | Damotte, Vincent | Defer, Gilles | Delgado, Silvia R | Deloukas, Panos | di Sapio, Alessia | Dilthey, Alexander T | Donnelly, Peter | Dubois, Bénédicte | Duddy, Martin | Edkins, Sarah | Elovaara, Irina | Esposito, Federica | Evangelou, Nikos | Fiddes, Barnaby | Field, Judith | Franke, Andre | Freeman, Colin | Frohlich, Irene Y | Galimberti, Daniela | Gieger, Christian | Gourraud, Pierre-Antoine | Graetz, Christiane | Graham, Andrew | Grummel, Verena | Guaschino, Clara | Hadjixenofontos, Athena | Hakonarson, Hakon | Halfpenny, Christopher | Hall, Gillian | Hall, Per | Hamsten, Anders | Harley, James | Harrower, Timothy | Hawkins, Clive | Hellenthal, Garrett | Hillier, Charles | Hobart, Jeremy | Hoshi, Muni | Hunt, Sarah E | Jagodic, Maja | Jelčić, Ilijas | Jochim, Angela | Kendall, Brian | Kermode, Allan | Kilpatrick, Trevor | Koivisto, Keijo | Konidari, Ioanna | Korn, Thomas | Kronsbein, Helena | Langford, Cordelia | Larsson, Malin | Lathrop, Mark | Lebrun-Frenay, Christine | Lechner-Scott, Jeannette | Lee, Michelle H | Leone, Maurizio A | Leppä, Virpi | Liberatore, Giuseppe | Lie, Benedicte A | Lill, Christina M | Lindén, Magdalena | Link, Jenny | Luessi, Felix | Lycke, Jan | Macciardi, Fabio | Männistö, Satu | Manrique, Clara P | Martin, Roland | Martinelli, Vittorio | Mason, Deborah | Mazibrada, Gordon | McCabe, Cristin | Mero, Inger-Lise | Mescheriakova, Julia | Moutsianas, Loukas | Myhr, Kjell-Morten | Nagels, Guy | Nicholas, Richard | Nilsson, Petra | Piehl, Fredrik | Pirinen, Matti | Price, Siân E | Quach, Hong | Reunanen, Mauri | Robberecht, Wim | Robertson, Neil P | Rodegher, Mariaemma | Rog, David | Salvetti, Marco | Schnetz-Boutaud, Nathalie C | Sellebjerg, Finn | Selter, Rebecca C | Schaefer, Catherine | Shaunak, Sandip | Shen, Ling | Shields, Simon | Siffrin, Volker | Slee, Mark | Sorensen, Per Soelberg | Sorosina, Melissa | Sospedra, Mireia | Spurkland, Anne | Strange, Amy | Sundqvist, Emilie | Thijs, Vincent | Thorpe, John | Ticca, Anna | Tienari, Pentti | van Duijn, Cornelia | Visser, Elizabeth M | Vucic, Steve | Westerlind, Helga | Wiley, James S | Wilkins, Alastair | Wilson, James F | Winkelmann, Juliane | Zajicek, John | Zindler, Eva | Haines, Jonathan L | Pericak-Vance, Margaret A | Ivinson, Adrian J | Stewart, Graeme | Hafler, David | Hauser, Stephen L | Compston, Alastair | McVean, Gil | De Jager, Philip | Sawcer, Stephen | McCauley, Jacob L
Nature genetics  2013;45(11):10.1038/ng.2770.
Using the ImmunoChip custom genotyping array, we analysed 14,498 multiple sclerosis subjects and 24,091 healthy controls for 161,311 autosomal variants and identified 135 potentially associated regions (p-value < 1.0 × 10-4). In a replication phase, we combined these data with previous genome-wide association study (GWAS) data from an independent 14,802 multiple sclerosis subjects and 26,703 healthy controls. In these 80,094 individuals of European ancestry we identified 48 new susceptibility variants (p-value < 5.0 × 10-8); three found after conditioning on previously identified variants. Thus, there are now 110 established multiple sclerosis risk variants in 103 discrete loci outside of the Major Histocompatibility Complex. With high resolution Bayesian fine-mapping, we identified five regions where one variant accounted for more than 50% of the posterior probability of association. This study enhances the catalogue of multiple sclerosis risk variants and illustrates the value of fine-mapping in the resolution of GWAS signals.
doi:10.1038/ng.2770
PMCID: PMC3832895  PMID: 24076602
17.  JC Polyomavirus Infection Is Strongly Controlled by Human Leucocyte Antigen Class II Variants 
PLoS Pathogens  2014;10(4):e1004084.
JC polyomavirus (JCV) carriers with a compromised immune system, such as in HIV, or subjects on immune-modulating therapies, such as anti VLA-4 therapy may develop progressive multifocal leukoencephalopathy (PML) which is a lytic infection of oligodendrocytes in the brain. Serum antibodies to JCV mark infection occur only in 50–60% of infected individuals, and high JCV-antibody titers seem to increase the risk of developing PML. We here investigated the role of human leukocyte antigen (HLA), instrumental in immune defense in JCV antibody response. Anti-JCV antibody status, as a surrogate for JCV infection, were compared to HLA class I and II alleles in 1621 Scandinavian persons with MS and 1064 population-based Swedish controls and associations were replicated in 718 German persons with MS. HLA-alleles were determined by SNP imputation, sequence specific (SSP) kits and a reverse PCR sequence-specific oligonucleotide (PCR-SSO) method. An initial GWAS screen displayed a strong HLA class II region signal. The HLA-DRB1*15 haplotype was strongly negatively associated to JCV sero-status in Scandinavian MS cases (OR = 0.42, p = 7×10−15) and controls (OR = 0.53, p = 2×10−5). In contrast, the DQB1*06:03 haplotype was positively associated with JCV sero-status, in Scandinavian MS cases (OR = 1.63, p = 0.006), and controls (OR = 2.69, p = 1×10−5). The German dataset confirmed these findings (OR = 0.54, p = 1×10−4 and OR = 1.58, p = 0.03 respectively for these haplotypes). HLA class II restricted immune responses, and hence CD4+ T cell immunity is pivotal for JCV infection control. Alleles within the HLA-DR1*15 haplotype are associated with a protective effect on JCV infection. Alleles within the DQB1*06:03 haplotype show an opposite association. These associations between JC virus antibody response and human leucocyte antigens supports the notion that CD4+ T cells are crucial in the immune defence to JCV and lays the ground for risk stratification for PML and development of therapy and prevention.
Author Summary
JC virus infection can lead to progressive multifocal leukoencephalopathy in individuals with a compromised immune system, such as during HIV infections or when treated with immunosuppressive or immunomodulating therapies. Progressive multifocal leukoencephalopathy is a rare but potentially fatal disease characterized by progressive damage of the brain white matter at multiple locations. It is therefore of importance to understand the host genetic control of response to JC virus in order to identify patients that can be treated with immunomodulating therapies, common treatments for autoimmune diseases, without increased risk for progressive multifocal leukoencephalopathy. This may also lead to development of preventative or curative anti-JC virus therapies. We here identify genetic variants being associated with JC virus antibody development; a negative association with the human leucocyte antigen DRB1*15-DQA1*01:02-DQB1*06:02 haplotype and a positive association with the DRB1*13-DQA1*01:03-DQB1*06:03 haplotype among controls and patients with multiple sclerosis from Scandinavia. We confirmed the associations in patients with multiple sclerosis from Germany. These associations between JC virus antibody response and human leucocyte antigens imply that CD4+ T cells are crucial in the immune defence and lay the ground for development of therapy and prevention.
doi:10.1371/journal.ppat.1004084
PMCID: PMC3999271  PMID: 24763718
18.  Regional differences regarding risk of developing Rheumatoid Arthritis in Stockholm County, Sweden 
Scandinavian journal of rheumatology  2013;42(5):10.3109/03009742.2013.769062.
Objectives
Rheumatoid arthritis (RA) is a complex disease that is associated with genetic and environmental factors. We have investigated geospatial variation in risk of developing RA within Stockholm County, with respect to established environmental risk factors for RA, as well as serologically-defined subgroups of RA.
Methods
Information regarding geographical location for 1432 cases and 2529 controls from the Epidemiological Investigation of Rheumatoid Arthritis (EIRA) study, living in Stockholm County at RA symptom onset, or matched date for controls, was used to estimate geospatial variation in risk. We used Generalized Additive Models (GAM) to create a risk surface, calculate odds ratios and adjust for potential confounding by smoking, educational level and RA within family. We performed a stratified analysis based on presence/absence of antibodies to citrullinated peptides (ACPA).
Results
We found significant spatial variation in the odds of developing RA in Stockholm County. After adjustment for smoking, educational level and family history of RA, this geospatial variation remained. The stratified analysis showed areas with higher odds ratios for ACPA-positive RA and ACPA-negative RA, after adjusting for smoking, educational level and having a family history of RA. Living in the city of Stockholm was associated with decreased risk of RA.
Conclusion
The risk of developing RA in Stockholm County is not evenly distributed and there are areas of increased risk that could not be explained by known factors. Further investigations of local exposures or social factors are warranted.
doi:10.3109/03009742.2013.769062
PMCID: PMC3815679  PMID: 23611369
Rheumatoid Arthritis; Epidemiologic methods; Antibodies; Geography; Risk; Smoking; ACPA; Stockholm
19.  Interaction between adolescent obesity and HLA risk genes in the etiology of multiple sclerosis 
Neurology  2014;82(10):865-872.
Objective:
We investigated potential interactions between human leukocyte antigen (HLA) genotype and body mass index (BMI) status in relation to the risk of developing multiple sclerosis (MS).
Methods:
We used 2 case-control studies, one with incident cases (1,510 cases, 2,017 controls) and one with prevalent cases (937 cases, 609 controls). Subjects with different genotypes and BMI were compared with regard to incidence of MS by calculating odds ratios (ORs) with 95% confidence intervals (CIs) employing logistic regression. Potential interactions between genotypes and BMI were evaluated by calculating the attributable proportion due to interaction.
Results:
In both cohorts, a significant interaction was observed between HLA-DRB1*15 and obesity, regardless of HLA-A*02 status. Similarly, there was a significant interaction between absence of A*02 and obesity, regardless of DRB1*15 status. In the incident cohort, obese subjects with the most susceptible genotype (carriage of DRB1*15 and absence of A*02) had an OR of 16.2 (95% CI 7.5–35.2) compared to nonobese subjects without the genetic risk factors. The corresponding OR in the prevalent study was 13.8 (95% CI 4.1–46.8).
Conclusions:
We observed striking interactions between BMI status and HLA genotype with regard to MS risk. Hypothetically, a low-grade inflammatory response inherent to obesity synergizes with the adaptive, HLA molecule–restricted arm of the immune system, causing MS. Prevention of adolescent obesity may thus lower the risk of developing MS, predominantly among people with a genetic susceptibility to the disease.
doi:10.1212/WNL.0000000000000203
PMCID: PMC3959752  PMID: 24500647
20.  Study protocol for examining job strain as a risk factor for severe unipolar depression in an individual participant meta-analysis of 14 European cohorts 
F1000Research  2014;2:233.
Background: Previous studies have shown that gainfully employed individuals with high work demands and low control at work (denoted “job strain”) are at increased risk of common mental disorders, including depression. Most existing studies have, however, measured depression using self-rated symptom scales that do not necessarily correspond to clinically diagnosed depression. In addition, a meta-analysis from 2008 indicated publication bias in the field.
Methods: This study protocol describes the planned design and analyses of an individual participant data meta-analysis, to examine whether job strain is associated with an increased risk of clinically diagnosed unipolar depression based on hospital treatment registers.  The study will be based on data from approximately 120,000 individuals who participated in 14 studies on work environment and health in 4 European countries. The self-reported working conditions data will be merged with national registers on psychiatric hospital treatment, primarily hospital admissions. Study-specific risk estimates for the association between job strain and depression will be calculated using Cox regressions. The study-specific risk estimates will be pooled using random effects meta-analysis.
Discussion: The planned analyses will help clarify whether job strain is associated with an increased risk of clinically diagnosed unipolar depression. As the analysis is based on pre-planned study protocols and an individual participant data meta-analysis, the pooled risk estimates will not be influenced by selective reporting and publication bias. However, the results of the planned study may only pertain to severe cases of unipolar depression, because of the outcome measure applied.
doi:10.12688/f1000research.2-233.v2
PMCID: PMC3938244  PMID: 24627793
21.  Job Strain and the Risk of Inflammatory Bowel Diseases: Individual-Participant Meta-Analysis of 95 000 Men and Women 
PLoS ONE  2014;9(2):e88711.
Background and Aims
Many clinicians, patients and patient advocacy groups believe stress to have a causal role in inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis. However, this is not corroborated by clear epidemiological research evidence. We investigated the association between work-related stress and incident Crohn's disease and ulcerative colitis using individual-level data from 95 000 European adults.
Methods
We conducted individual-participant data meta-analyses in a set of pooled data from 11 prospective European studies. All studies are a part of the IPD-Work Consortium. Work-related psychosocial stress was operationalised as job strain (a combination of high demands and low control at work) and was self-reported at baseline. Crohn's disease and ulcerative colitis were ascertained from national hospitalisation and drug reimbursement registers. The associations between job strain and inflammatory bowel disease outcomes were modelled using Cox proportional hazards regression. The study-specific results were combined in random effects meta-analyses.
Results
Of the 95 379 participants who were free of inflammatory bowel disease at baseline, 111 men and women developed Crohn's disease and 414 developed ulcerative colitis during follow-up. Job strain at baseline was not associated with incident Crohn's disease (multivariable-adjusted random effects hazard ratio: 0.83, 95% confidence interval: 0.48, 1.43) or ulcerative colitis (hazard ratio: 1.06, 95% CI: 0.76, 1.48). There was negligible heterogeneity among the study-specific associations.
Conclusions
Our findings suggest that job strain, an indicator of work-related stress, is not a major risk factor for Crohn's disease or ulcerative colitis.
doi:10.1371/journal.pone.0088711
PMCID: PMC3928274  PMID: 24558416
22.  A genome-wide association study of anorexia nervosa 
Boraska, Vesna | Franklin, Christopher S | Floyd, James AB | Thornton, Laura M | Huckins, Laura M | Southam, Lorraine | Rayner, N William | Tachmazidou, Ioanna | Klump, Kelly L | Treasure, Janet | Lewis, Cathryn M | Schmidt, Ulrike | Tozzi, Federica | Kiezebrink, Kirsty | Hebebrand, Johannes | Gorwood, Philip | Adan, Roger AH | Kas, Martien JH | Favaro, Angela | Santonastaso, Paolo | Fernández-Aranda, Fernando | Gratacos, Monica | Rybakowski, Filip | Dmitrzak-Weglarz, Monika | Kaprio, Jaakko | Keski-Rahkonen, Anna | Raevuori, Anu | Van Furth, Eric F | Slof-Op t Landt, Margarita CT | Hudson, James I | Reichborn-Kjennerud, Ted | Knudsen, Gun Peggy S | Monteleone, Palmiero | Kaplan, Allan S | Karwautz, Andreas | Hakonarson, Hakon | Berrettini, Wade H | Guo, Yiran | Li, Dong | Schork, Nicholas J. | Komaki, Gen | Ando, Tetsuya | Inoko, Hidetoshi | Esko, Tõnu | Fischer, Krista | Männik, Katrin | Metspalu, Andres | Baker, Jessica H | Cone, Roger D | Dackor, Jennifer | DeSocio, Janiece E | Hilliard, Christopher E | O’Toole, Julie K | Pantel, Jacques | Szatkiewicz, Jin P | Taico, Chrysecolla | Zerwas, Stephanie | Trace, Sara E | Davis, Oliver SP | Helder, Sietske | Bühren, Katharina | Burghardt, Roland | de Zwaan, Martina | Egberts, Karin | Ehrlich, Stefan | Herpertz-Dahlmann, Beate | Herzog, Wolfgang | Imgart, Hartmut | Scherag, André | Scherag, Susann | Zipfel, Stephan | Boni, Claudette | Ramoz, Nicolas | Versini, Audrey | Brandys, Marek K | Danner, Unna N | de Kovel, Carolien | Hendriks, Judith | Koeleman, Bobby PC | Ophoff, Roel A | Strengman, Eric | van Elburg, Annemarie A | Bruson, Alice | Clementi, Maurizio | Degortes, Daniela | Forzan, Monica | Tenconi, Elena | Docampo, Elisa | Escaramís, Geòrgia | Jiménez-Murcia, Susana | Lissowska, Jolanta | Rajewski, Andrzej | Szeszenia-Dabrowska, Neonila | Slopien, Agnieszka | Hauser, Joanna | Karhunen, Leila | Meulenbelt, Ingrid | Slagboom, P Eline | Tortorella, Alfonso | Maj, Mario | Dedoussis, George | Dikeos, Dimitris | Gonidakis, Fragiskos | Tziouvas, Konstantinos | Tsitsika, Artemis | Papezova, Hana | Slachtova, Lenka | Martaskova, Debora | Kennedy, James L. | Levitan, Robert D. | Yilmaz, Zeynep | Huemer, Julia | Koubek, Doris | Merl, Elisabeth | Wagner, Gudrun | Lichtenstein, Paul | Breen, Gerome | Cohen-Woods, Sarah | Farmer, Anne | McGuffin, Peter | Cichon, Sven | Giegling, Ina | Herms, Stefan | Rujescu, Dan | Schreiber, Stefan | Wichmann, H-Erich | Dina, Christian | Sladek, Rob | Gambaro, Giovanni | Soranzo, Nicole | Julia, Antonio | Marsal, Sara | Rabionet, Raquel | Gaborieau, Valerie | Dick, Danielle M | Palotie, Aarno | Ripatti, Samuli | Widén, Elisabeth | Andreassen, Ole A | Espeseth, Thomas | Lundervold, Astri | Reinvang, Ivar | Steen, Vidar M | Le Hellard, Stephanie | Mattingsdal, Morten | Ntalla, Ioanna | Bencko, Vladimir | Foretova, Lenka | Janout, Vladimir | Navratilova, Marie | Gallinger, Steven | Pinto, Dalila | Scherer, Stephen | Aschauer, Harald | Carlberg, Laura | Schosser, Alexandra | Alfredsson, Lars | Ding, Bo | Klareskog, Lars | Padyukov, Leonid | Finan, Chris | Kalsi, Gursharan | Roberts, Marion | Logan, Darren W | Peltonen, Leena | Ritchie, Graham RS | Barrett, Jeffrey C | Estivill, Xavier | Hinney, Anke | Sullivan, Patrick F | Collier, David A | Zeggini, Eleftheria | Bulik, Cynthia M
Molecular psychiatry  2010;16(9):10.1038/mp.2010.107.
Anorexia nervosa (AN) is a complex and heritable eating disorder characterized by dangerously low body weight. Neither candidate gene studies nor an initial genome wide association study (GWAS) have yielded significant and replicated results. We performed a GWAS in 2,907 cases with AN from 14 countries (15 sites) and 14,860 ancestrally matched controls as part of the Genetic Consortium for AN (GCAN) and the Wellcome Trust Case Control Consortium 3 (WTCCC3). Individual association analyses were conducted in each stratum and meta-analyzed across all 15 discovery datasets. Seventy-six (72 independent) SNPs were taken forward for in silico (two datasets) or de novo (13 datasets) replication genotyping in 2,677 independent AN cases and 8,629 European ancestry controls along with 458 AN cases and 421 controls from Japan. The final global meta-analysis across discovery and replication datasets comprised 5,551 AN cases and 21,080 controls. AN subtype analyses (1,606 AN restricting; 1,445 AN binge-purge) were performed. No findings reached genome-wide significance. Two intronic variants were suggestively associated: rs9839776 (P=3.01×10−7) in SOX2OT and rs17030795 (P=5.84×10−6) in PPP3CA. Two additional signals were specific to Europeans: rs1523921 (P=5.76×10−6) between CUL3 and FAM124B and rs1886797 (P=8.05×10−6) near SPATA13. Comparing discovery to replication results, 76% of the effects were in the same direction, an observation highly unlikely to be due to chance (P= 4×10−6), strongly suggesting that true findings exist but that our sample, the largest yet reported, was underpowered for their detection. The accrual of large genotyped AN case-control samples should be an immediate priority for the field.
doi:10.1038/mp.2010.107
PMCID: PMC3859494  PMID: 21079607
anorexia nervosa; eating disorders; GWAS; genome-wide association study; body mass index; metabolic
23.  Epidemiology of Environmental Exposures and Human Autoimmune Diseases: Findings from a National Institute of Environmental Health Sciences Expert Panel Workshop 
Journal of autoimmunity  2012;39(4):259-271.
Autoimmune diseases (AID) are a collection of many complex disorders of unknown etiology resulting in immune responses to self-antigens and are thought to result from interactions between genetic and environmental factors. Here we review the epidemiologic evidence for the role of environmental factors in the development of human AID, the conclusions that can be drawn from the existing data, critical knowledge gaps, and research needed to fill these gaps and to resolve uncertainties. We specifically summarize the state of knowledge and our levels of confidence in the role of specific agents in the development of autoimmune diseases, and we define the areas of greatest impact for future investigations. Among our consensus findings we are confident that: 1) crystalline silica exposure can contribute to the development of several AID; 2) solvent exposure can contribute to the development of systemic sclerosis; 3) smoking can contribute to the development of seropositive rheumatoid arthritis; and 4) an inverse association exists between ultraviolet radiation exposure and the risk of development of multiple sclerosis. We suggest that more studies of phenotypes, genotypes, and multiple exposures are needed. Additional knowledge gaps needing investigation include: defining important windows in the timing of exposures and latencies relating to age, developmental state, and hormonal changes; understanding dose-response relationships; and elucidating mechanisms for disease development. Addressing these essential issues will require more resources to support research, particularly of rare AID, but knowledge of the risks conferred by environmental factors in specific genetic contexts could pave the way for prevention of AID in the future.
doi:10.1016/j.jaut.2012.05.002
PMCID: PMC3496812  PMID: 22739348
autoimmune disease; environmental risk factors; biologic agents; chemical agents; physical factors; research priorities
24.  Study protocol for examining job strain as a risk factor for severe unipolar depression in an individual participant meta-analysis of 14 European cohorts 
F1000Research  2013;2:233.
Background: Previous studies have shown that gainfully employed individuals with high work demands and low control at work (denoted “job strain”) are at increased risk of common mental disorders, including depression. Most existing studies have, however, measured depression using self-rated symptom scales that do not necessarily correspond to clinically diagnosed depression. In addition, a meta-analysis from 2008 indicated publication bias in the field.
 
Methods: This study protocol describes the planned design and analyses of an individual participant data meta-analysis, to examine whether job strain is associated with an increased risk of clinically diagnosed unipolar depression based on hospital treatment registers.  The study will be based on data from approximately 120,000 individuals who participated in 14 studies on work environment and health in 4 European countries. The self-reported working conditions data will be merged with national registers on psychiatric hospital treatment, primarily hospital admissions. Study-specific risk estimates for the association between job strain and depression will be calculated using Cox regressions. The study-specific risk estimates will be pooled using random effects meta-analysis.
 
Discussion: The planned analyses will help clarify whether job strain is associated with an increased risk of clinically diagnosed unipolar depression. As the analysis is based on pre-planned study protocols and an individual participant data meta-analysis, the pooled risk estimates will not be influenced by selective reporting and publication bias. However, the results of the planned study may only pertain to severe cases of unipolar depression, because of the outcome measure applied.
doi:10.12688/f1000research.2-233.v1
PMCID: PMC3938244  PMID: 24627793
25.  Smoking and multiple sclerosis susceptibility 
European Journal of Epidemiology  2013;28(11):867-874.
Smoking is one of the most established risk factors for multiple sclerosis (MS). The aim of this study was to investigate how age at smoking debut, duration, intensity and cumulative dose of smoking, and smoking cessation influence the association between smoking and MS risk. In two Swedish population-based case–control studies (7,883 cases, 9,264 controls), subjects with different smoking habits were compared regarding MS risk, by calculating odds ratios with 95 % confidence intervals. We observed a clear dose response association between cumulative dose of smoking and MS risk (p value for trend <10−35). Both duration and intensity of smoking contributed independently to the increased risk of MS. However, the detrimental effect of smoking abates a decade after smoking cessation regardless of the cumulative dose of smoking. Age at smoking debut did not affect the association between smoking and MS. Smoking increases the risk of MS in a dose response manner. However, in contrary to several other risk factors for MS that seem to affect the risk only if the exposure takes place during a specific period in life, smoking affects MS risk regardless of age at exposure, and the detrimental effect slowly abates after smoking cessation.
Electronic supplementary material
The online version of this article (doi:10.1007/s10654-013-9853-4) contains supplementary material, which is available to authorized users.
doi:10.1007/s10654-013-9853-4
PMCID: PMC3898140  PMID: 24146047
Multiple sclerosis; Smoking; Case–control study

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