Observational analytic studies in multiple sclerosis: controlling bias through study design and conduct. The Australian Multicentre Study of Environment and Immune Function

HLA-DRB1*15:01 and the MERTK Gene Interact to Selectively Influence the Profile of MERTK-Expressing Monocytes in Both Health and MS

BACKGROUND AND OBJECTIVES

HLA-DRB1*15:01 (DR15) and MERTK are 2 risk genes for multiple sclerosis (MS). The variant rs7422195 is an expression quantitative trait locus for MERTK in CD14+ monocytes; cells with phagocytic and immunomodulatory potential. We aimed to understand how drivers of disease risk and pathogenesis vary with HLA and MERTK genotype and disease activity.

METHODS

We investigated how proportions of monocytes vary with HLA and MERTK genotype and disease activity in MS. CD14+ monocytes were isolated from patients with MS at relapse (n = 40) and 3 months later (n = 23). Healthy controls (HCs) underwent 2 blood collections 3 months apart. Immunophenotypic profiling of monocytes was performed by flow cytometry. Methylation of 35 CpG sites within and near the MERTK gene was assessed in whole blood samples of individuals experiencing their first episode of clinical CNS demyelination (n = 204) and matched HCs (n = 345) using an Illumina EPIC array.

RESULTS

DR15-positive patients had lower proportions of CD14+ MERTK+ monocytes than DR15-negative patients, independent of genotype at the MERTK SNP rs7422195. Proportions of CD14+ MERTK+ monocytes were further reduced during relapse in DR15-positive but not DR15-negative patients. Patients homozygous for the major G allele at rs7422195 exhibited higher proportions of CD14+ MERTK+ monocytes at both relapse and remission compared with controls. We observed that increased methylation of the MERTK gene was significantly associated with the presence of DR15.

DISCUSSION

DR15 and MERTK genotype independently influence proportions of CD14+ MERTK+ monocytes in MS. We confirmed previous observations that the MERTK risk SNP rs7422195 is associated with altered MERTK expression in monocytes. We identified that expression of MERTK is stratified by disease in people homozygous for the major G allele of rs7422195. The finding that the proportion of CD14+ MERTK+ monocytes is reduced in DR15-positive individuals supports prior data identifying genetic links between these 2 loci in influencing MS risk. DR15 genotype-dependent alterations in methylation of the MERTK gene provides a molecular link between these loci and identifies a potential mechanism by which MERTK expression is influenced by DR15. This links DR15 haplotype to MS susceptibility beyond direct influence on antigen presentation and suggests the need for HLA-based stratification of approaches to MERTK as a therapeutic target.

Examining the environmental risk factors of progressive-onset and relapsing-onset multiple sclerosis: recruitment challenges, potential bias, and statistical strategies

It is unknown whether the currently known risk factors of multiple sclerosis reflect the etiology of progressive-onset multiple sclerosis (POMS) as observational studies rarely included analysis by type of onset. We designed a case-control study to examine associations between environmental factors and POMS and compared effect sizes to relapse-onset MS (ROMS), which will offer insights into the etiology of POMS and potentially contribute to prevention and intervention practice. This study utilizes data from the Primary Progressive Multiple Sclerosis (PPMS) Study and the Australian Multi-center Study of Environment and Immune Function (the AusImmune Study). This report outlines the conduct of the PPMS Study, whether the POMS sample is representative, and the planned analysis methods. The study includes 155 POMS, 204 ROMS, and 558 controls. The distributions of the POMS were largely similar to Australian POMS patients in the MSBase Study, with 54.8% female, 85.8% POMS born before 1970, mean age of onset of 41.44 ± 8.38 years old, and 67.1% living between 28.9 and 39.4° S. The POMS were representative of the Australian POMS population. There are some differences between POMS and ROMS/controls (mean age at interview: POMS 55 years vs. controls 40 years; sex: POMS 53% female vs. controls 78% female; location of residence: 14.3% of POMS at a latitude ≤ 28.9°S vs. 32.8% in controls), which will be taken into account in the analysis. We discuss the methodological issues considered in the study design, including prevalence-incidence bias, cohort effects, interview bias and recall bias, and present strategies to account for it. Associations between exposures of interest and POMS/ROMS will be presented in subsequent publications.

Risk of a first clinical diagnosis of central nervous system demyelination in relation to human herpesviruses in the context of Epstein-Barr virus

BACKGROUND AND PURPOSE

Epstein-Barr virus (EBV) is implicated in multiple sclerosis (MS) risk; evidence for other herpesviruses is inconsistent. Here, we test blood markers of infection with human herpesvirus 6 (HHV-6), varicella zoster virus (VZV), and cytomegalovirus (CMV) as risk factors for a first clinical diagnosis of central nervous system demyelination (FCD) in the context of markers of EBV infection.

METHODS

In the Ausimmune case-control study, cases had an FCD, and population controls were matched on age, sex, and study region. We quantified HHV-6- and VZV-DNA load in whole blood and HHV-6, VZV, and CMV antibodies in serum. Conditional logistic regression tested associations with FCD risk, adjusting for Epstein-Barr nuclear antigen (EBNA) IgG, EBV-DNA load, and other covariates.

RESULTS

In 204 FCD cases and 215 matched controls, only HHV-6-DNA load (positive vs. negative) was associated with FCD risk (adjusted odds ratio = 2.20, 95% confidence interval = 1.08-4.46, p = 0.03). Only EBNA IgG and HHV-6-DNA positivity were retained in a predictive model of FCD risk; the combination had a stronger association than either alone. CMV-specific IgG concentration modified the association between an MS risk-related human leucocyte antigen gene and FCD risk. Six cases and one control had very high HHV-6-DNA load (>1.0 × 106 copies/mL).

CONCLUSIONS

HHV-6-DNA positivity and high load (possibly due to inherited HHV-6 chromosomal integration) were associated with increased FCD risk, particularly in association with markers of EBV infection. With growing interest in prevention/management of MS through EBV-related pathways, there should be additional consideration of the role of HHV-6 infection.

Evaluation of Cell-Specific Epigenetic Age Acceleration in People With Multiple Sclerosis

BACKGROUND AND OBJECTIVES

In multiple sclerosis (MS), accelerated aging of the immune system (immunosenescence) may be associated with disease onset or drive progression. DNA methylation (DNAm) is an epigenetic factor that varies among lymphocyte subtypes, and cell-specific DNAm is associated with MS. DNAm varies across the life span and can be used to accurately estimate biological age acceleration, which has been linked to a range of morbidities. The objective of this study was to test for cell-specific epigenetic age acceleration (EAA) in people with MS.

METHODS

This was a case-control study of EAA using existing DNAm data from several independent previously published studies. Data were included if .idat files from Illumina 450K or EPIC arrays were available for both a case with MS and an age-matched and sex-matched control, from the same study. Multifactor statistical modeling was performed to assess the primary outcome of EAA. We explored the relationship of EAA and MS, including interaction terms to identify immune cell-specific effects. Cell-sorted DNA methylation data from 3 independent datasets were used to validate findings.

RESULTS

We used whole blood DNA methylation data from 583 cases with MS and 643 non-MS controls to calculate EAA using the GrimAge algorithm. The MS group exhibited an increased EAA compared with controls (approximately 9 mths, 95% CI 3.6-14.4), p = 0.001). Statistical deconvolution showed that EAA is associated with MS in a B cell-dependent manner (β int = 1.7, 95% CI 0.3-2.8), p = 0.002), irrespective of B-cell proportions. Validation analysis using 3 independent datasets enriched for B cells showed an EAA increase of 5.1 years in cases with MS compared with that in controls (95% CI 2.8-7.4, p = 5.5 × 10-5). By comparison, there was no EAA difference in MS in a T cell-enriched dataset. We found that EAA was attributed to the DNAm surrogates for Beta-2-microglobulin (difference = 47,546, 95% CI 10,067-85,026; p = 7.2 × 10-5), and smoking pack-years (difference = 8.1, 95% CI 1.9-14.2, p = 0.002).

DISCUSSION

This study provides compelling evidence that B cells exhibit marked EAA in MS and supports the hypothesis that premature B-cell immune senescence plays a role in MS. Future MS studies should focus on age-related molecular mechanisms in B cells.

DNA Methylation Signatures of Multiple Sclerosis Occur Independently of Known Genetic Risk and Are Primarily Attributed to B Cells and Monocytes

Epigenetic mechanisms can regulate how DNA is expressed independently of sequence and are known to be associated with various diseases. Among those epigenetic mechanisms, DNA methylation (DNAm) is influenced by genotype and the environment, making it an important molecular interface for studying disease etiology and progression. In this study, we examined the whole blood DNA methylation profiles of a large group of people with (pw) multiple sclerosis (MS) compared to those of controls. We reveal that methylation differences in pwMS occur independently of known genetic risk loci and show that they more strongly differentiate disease (AUC = 0.85, 95% CI 0.82-0.89, p = 1.22 × 10-29) than known genetic risk loci (AUC = 0.72, 95% CI: 0.66-0.76, p = 9.07 × 10-17). We also show that methylation differences in MS occur predominantly in B cells and monocytes and indicate the involvement of cell-specific biological pathways. Overall, this study comprehensively characterizes the immune cell-specific epigenetic architecture of MS.

The association between disability progression, relapses, and treatment in early relapse onset MS: an observational, multi-centre, longitudinal cohort study

The indirect contribution of multiple sclerosis (MS) relapses to disability worsening outcomes, and vice-versa, remains unclear. Disease modifying therapies (DMTs) are potential modulators of this association. Understanding how these endo-phenotypes interact may provide insights into disease pathogenesis and treatment practice in relapse-onset MS (ROMS). Utilising a unique, prospectively collected clinical data from a longitudinal cohort of 279 first demyelinating event cases followed for up to 15 years post-onset, we examined indirect associations between relapses and treatment and the risk of disability worsening, and vice-versa. Indirect association parameters were estimated using joint models for longitudinal and survival data. Early relapses within 2.5 years of MS onset predicted early disability worsening outcomes (HR = 3.45, C.I 2.29-3.61) per relapse, but did not contribute to long-term disability worsening thereinafter (HR = 0.21, C.I 0.15-0.28). Conversely, disability worsening outcomes significantly contributed to relapse risk each year (HR = 2.96, C.I 2.91-3.02), and persisted over time (HR = 3.34, C.I 2.90-3.86), regardless of DMT treatments. The duration of DMTs significantly reduced the hazards of relapses (1st-line DMTs: HR = 0.68, C.I 0.58-0.79; 3rd-line DMTs: HR = 0.37, C.I 0.32-0.44) and disability worsening events (1st-line DMTs: HR = 0.74, C.I 0.69-0.79; 3rd-line DMTs: HR = 0.90, C.I 0.85-0.95), respectively. Results from time-dynamic survival probabilities further revealed individuals having higher risk of future relapses and disability worsening outcomes, respectively. The study provided evidence that in ROMS, relapses accrued within 2.5 years of MS onset are strong indicators of disability worsening outcomes, but late relapses accrued 2.5 years post onset are not overt risk factors for further disability worsening. In contrast, disability worsening outcomes are strong positive predictors of current and subsequent relapse risk. Long-term DMT use and older age strongly influence the individual outcomes and their associations.

Interferon beta treatment is a potent and targeted epigenetic modifier in multiple sclerosis

Introduction

Multiple Sclerosis (MS) has a complex pathophysiology that involves genetic and environmental factors. DNA methylation (DNAm) is one epigenetic mechanism that can reversibly modulate gene expression. Cell specific DNAm changes have been associated with MS, and some MS therapies such as dimethyl fumarate can influence DNAm. Interferon Beta (IFNβ), was one of the first disease modifying therapies in multiple sclerosis (MS). However, how IFNβ reduces disease burden in MS is not fully understood and little is known about the precise effect of IFNβ treatment on methylation.

Methods

The objective of this study was to determine the changes in DNAm associated with INFβ use, using methylation arrays and statistical deconvolutions on two separate datasets (total ntreated = 64, nuntreated = 285).

Results

We show that IFNβ treatment in people with MS modifies the methylation profile of interferon response genes in a strong, targeted, and reproducible manner. Using these identified methylation differences, we constructed a methylation treatment score (MTS) that is an accurate discriminator between untreated and treated patients (Area under the curve = 0.83). This MTS is time-sensitive and in consistent with previously identified IFNβ treatment therapeutic lag. This suggests that methylation changes are required for treatment efficacy. Overrepresentation analysis found that IFNβ treatment recruits the endogenous anti-viral molecular machinery. Finally, statistical deconvolution revealed that dendritic cells and regulatory CD4+ T cells were most affected by IFNβ induced methylation changes.

Discussion

In conclusion, our study shows that IFNβ treatment is a potent and targeted epigenetic modifier in multiple sclerosis.

Higher consumption of ultra-processed foods and increased likelihood of central nervous system demyelination in a case-control study of Australian adults

BACKGROUND

Consumption of ultra-processed foods (UPFs) has been linked to risk of chronic diseases, with scant evidence in relation to multiple sclerosis (MS).

METHODS

We tested associations between UPF consumption and likelihood of a first clinical diagnosis of central nervous system demyelination (FCD) (267 cases, 508 controls), a common precursor to MS. We used data from the 2003-2006 Ausimmune Study and logistic regression with full propensity score matching for age, sex, region of residence, education, smoking history, body mass index, physical activity, history of infectious mononucleosis, dietary misreporting, and total energy intake.

RESULTS

Higher UPF consumption was statistically significantly associated with an increased likelihood of FCD (adjusted odds ratio = 1.08; 95% confidence interval = 1.0,1.15; p = 0.039), representing an 8% increase in likelihood of FCD per one energy-adjusted serving/day of UPFs.

CONCLUSION

Higher intakes of UPF were associated with increased likelihood of FCD in this Australian cohort. Nutrition education and awareness of healthy eating patterns may benefit those at high risk of FCD.

Genetically determined serum serine level has a novel causal effect on multiple sclerosis risk and predicts disability progression

BACKGROUND

There are currently no specific biomarkers for multiple sclerosis (MS). Identifying robust biomarkers for MS is crucial to improve disease diagnosis and management.

METHODS

This study first used six Mendelian randomisation methods to assess causal relationship of 174 metabolites with MS, incorporating data from European-ancestry metabolomics (n=8569-86 507) and MS (n=14 802 MS cases, 26 703 controls) genomewide association studies. Genetic scores for identified causal metabolite(s) were then computed to predict MS disability progression in an independent longitudinal cohort (AusLong study) of 203 MS cases with up to 15-year follow-up.

RESULTS

We found a novel genetic causal effect of serine on MS onset (OR=1.67, 95% CI 1.51 to 1.84, p=1.73×10^-20), such that individuals whose serine level is 1 SD above the population mean will have 1.67 times the risk of developing MS. This is robust across all sensitivity methods (OR ranges from 1.49 to 1.67). In an independent longitudinal MS cohort, we then constructed time-dynamic and time-fixed genetic scores based on serine genetic instrument single-nucleotide polymorphisms, where higher scores for raised serum serine level were associated with increased risk of disability worsening, especially in the time-dynamic model (RR=1.25, 95% CI 1.10 to 1.42, p=7.52×10^-4).

CONCLUSIONS

These findings support investigating serine as an important candidate biomarker for MS onset and disability progression.

Ensemble machine learning identifies genetic loci associated with future worsening of disability in people with multiple sclerosis

Limited studies have been conducted to identify and validate multiple sclerosis (MS) genetic loci associated with disability progression. We aimed to identify MS genetic loci associated with worsening of disability over time, and to develop and validate ensemble genetic learning model(s) to identify people with MS (PwMS) at risk of future worsening. We examined associations of 208 previously established MS genetic loci with the risk of worsening of disability; we learned ensemble genetic decision rules and validated the predictions in an external dataset. We found 7 genetic loci (rs7731626: HR 0.92, P = 2.4 × 10^-5; rs12211604: HR 1.16, P = 3.2 × 10^-7; rs55858457: HR 0.93, P = 3.7 × 10^-7; rs10271373: HR 0.90, P = 1.1 × 10^-7; rs11256593: HR 1.13, P = 5.1 × 10^-57; rs12588969: HR = 1.10, P = 2.1 × 10^-10; rs1465697: HR 1.09, P = 1.7 × 10^-128) associated with risk worsening of disability; most of which were located near or tagged to 13 genomic regions enriched in peptide hormones and steroids biosynthesis pathways by positional and eQTL mapping. The derived ensembles produced a set of genetic decision rules that can be translated to provide additional prognostic values to existing clinical predictions, with the additional benefit of incorporating relevant genetic information into clinical decision making for PwMS. The present study extends our knowledge of MS progression genetics and provides the basis of future studies regarding the functional significance of the identified loci.

Predictors of progression from a first demyelinating event to clinically definite multiple sclerosis

Understanding the predictors of progression from a first to a second demyelinating event (and formerly, a diagnosis of clinically definite multiple sclerosis) is important clinically. Previous studies have focused on predictors within a single domain, e.g. radiological, lacking prospective data across multiple domains. We tested a comprehensive set of personal, environmental, neurological, MRI and genetic characteristics, considered together, as predictors of progression from a first demyelinating event to clinically definite multiple sclerosis. Participants were aged 18–59 years and had a first demyelinating event during the study recruitment period (1 November 2003–31 December 2006) for the Ausimmune Study (n = 216) and had follow-up data to 2–3 years post-initial interview. Detailed baseline data were available on a broad range of demographic and environmental factors, MRI, and genetic and viral studies. Follow-up data included confirmation of clinically definite multiple sclerosis (or not) and changes in environmental exposures during the follow-up period. We used multivariable logistic regression and Cox proportional hazards regression modelling to test predictors of, and time to, conversion to clinically definite multiple sclerosis. On review, one participant had an undiagnosed event prior to study recruitment and was excluded (n = 215). Data on progression to clinically definite multiple sclerosis were available for 91.2% (n = 196); 77% were diagnosed as clinically definite multiple sclerosis at follow-up. Mean (standard deviation) duration of follow-up was 2.7 (0.7) years. The set of predictors retained in the best predictive model for progression from a first demyelinating event to clinically definite multiple sclerosis were as follows: younger age at first demyelinating event [adjusted odds ratio (aOR) = 0.92, 95% confidence interval (CI) = 0.87–0.97, per additional year of age); being a smoker at baseline (versus not) (aOR = 2.55, 95% CI 0.85–7.69); lower sun exposure at age 6–18 years (aOR = 0.86, 95% CI 0.74–1.00, per 100 kJ/m² increment in ultraviolet radiation dose), presence (versus absence) of infratentorial lesions on baseline magnetic resonance imaging (aOR = 7.41, 95% CI 2.08–26.41); and single nucleotide polymorphisms in human leukocyte antigen (HLA)-B (rs2523393, aOR = 0.25, 95% CI 0.09–0.68, for any G versus A:A), TNFRSF1A (rs1800693, aOR = 5.82, 95% CI 2.10–16.12, for any C versus T:T), and a vitamin D-binding protein gene (rs7041, aOR = 3.76, 95% CI 1.41–9.99, for any A versus C:C). The final model explained 36% of the variance. Predictors of more rapid progression to clinically definite multiple sclerosis (Cox proportional hazards regression) were similar. Genetic and magnetic resonance imaging characteristics as well as demographic and environmental factors predicted progression, and more rapid progression, from a first demyelinating event to a second event and clinically definite multiple sclerosis.

Total Dairy Consumption Is Not Associated With Likelihood of a First Clinical Diagnosis of Central Nervous System Demyelination

Background

The evidence associating consumption of dairy products and risk of MS is contradictory and inconclusive.

Objective

To test associations between dairy consumption and the likelihood of a first clinical diagnosis of central nervous system demyelination (FCD), a common precursor to MS.

Methods

We used data from the 2003–2006 Ausimmune Study, a population-based Australian, multicentre, matched case-control study (272 cases, 519 controls). Total dairy consumption (servings/day) was calculated by summing consumption of milk, cheese and yogurt. Covariate-adjusted treatment effects using augmented inverse probability weighting was used to test for associations with FCD. We conducted sensitivity analyses in the subset of participants who had had a classic first demyelinating event (FDE), defined as a single, first episode of symptoms suggestive of CNS demyelination.

Results

There were no statistically significant associations between total dairy consumption (per one serving/day) and FCD (adjusted OR 1.00; 95% CI 0.93, 1.07; p = 0.979). However, yogurt consumption (vs. no yogurt consumption) was associated with an 11% decreased likelihood of FDE (adjusted OR 0.89; 95% CI 0.89, 0.79; p = 0.046).

Conclusion

While total dairy consumption was not associated with FCD in this Australian case-control study, yogurt consumption was associated with reduced likelihood of FDE.

Vitamin D metabolites and risk of first clinical diagnosis of central nervous system demyelination

Low 25-hydroxyvitamin D (25(OH)D) concentration is a recognised risk factor for multiple sclerosis (MS). Associations with vitamin D metabolites and vitamin D binding globulin (VDBG) have not been widely studied. We assessed the association between vitamin D metabolites (25(OH)D₂, 25(OH)D₃, c3-epimer 25(OH)D₃, 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃), and 24,25-dihydroxyvitamin D₃ (24,25(OH)₂D₃)) measured by liquid chromatography-tandem mass spectrometry assays, VDBG measured using a polyclonal immunoassay, and calculated free and bioavailable 25(OH)D, free 1,25(OH)₂D₃, and the 24,25(OH)₂D₃: total 25(OH)D and total 1,25(OH)₂D: total 25(OH)D ratios with risk of a first clinical diagnosis of CNS demyelination (FCD) in an Australian case-control study (n = 196 cases, n = 241 controls, matched on age, sex and study region). Higher 25(OH)D (adjusted odds ratio (AOR) = 0.94 (95 % confidence interval (CI) 0.85-1.03) per 10 nmol/L increment) and 24,25(OH)₂D₃ (AOR = 0.81 (95 %CI 0.65-1.00) per 1 nmol/L increment) concentrations were associated with reduced FCD risk. Our results were compatible with no association for the other vitamin D metabolites, ratios, or VDBG with FCD risk. Thus, using standardised assays, and a comprehensive range of vitamin D metabolites, we confirmed the association of higher 25(OH)D and reduced FCD risk, and describe a similar effect for 24,25(OH)₂D₃; free or bioavailable 25(OH)D were not associated with FCD risk.

Developing a clinical-environmental-genotypic prognostic index for relapsing-onset multiple sclerosis and clinically isolated syndrome

Our inability to reliably predict disease outcomes in multiple sclerosis remains an issue for clinicians and clinical trialists. This study aims to create, from available clinical, genetic and environmental factors; a clinical–environmental–genotypic prognostic index to predict the probability of new relapses and disability worsening. The analyses cohort included prospectively assessed multiple sclerosis cases (N = 253) with 2858 repeated observations measured over 10 years. N = 219 had been diagnosed as relapsing-onset, while N = 34 remained as clinically isolated syndrome by the 10th-year review. Genotype data were available for 199 genetic variants associated with multiple sclerosis risk. Penalized Cox regression models were used to select potential genetic variants and predict risk for relapses and/or worsening of disability. Multivariable Cox regression models with backward elimination were then used to construct clinical–environmental, genetic and clinical–environmental–genotypic prognostic index, respectively. Robust time-course predictions were obtained by Landmarking. To validate our models, Weibull calibration models were used, and the Chi-square statistics, Harrell’s C-index and pseudo-R² were used to compare models. The predictive performance at diagnosis was evaluated using the Kullback–Leibler and Brier (dynamic) prediction error (reduction) curves. The combined index (clinical–environmental–genotypic) predicted a quadratic time-dynamic disease course in terms of worsening (HR = 2.74, CI: 2.00–3.76; pseudo-R²=0.64; C-index = 0.76), relapses (HR = 2.16, CI: 1.74–2.68; pseudo-R² = 0.91; C-index = 0.85), or both (HR = 3.32, CI: 1.88–5.86; pseudo-R² = 0.72; C-index = 0.77). The Kullback–Leibler and Brier curves suggested that for short-term prognosis (≤5 years from diagnosis), the clinical–environmental components of disease were more relevant, whereas the genetic components reduced the prediction errors only in the long-term (≥5 years from diagnosis). The combined components performed slightly better than the individual ones, although their prognostic sensitivities were largely modulated by the clinical–environmental components. We have created a clinical–environmental–genotypic prognostic index using relevant clinical, environmental, and genetic predictors, and obtained robust dynamic predictions for the probability of developing new relapses and worsening of symptoms in multiple sclerosis. Our prognostic index provides reliable information that is relevant for long-term prognostication and may be used as a selection criterion and risk stratification tool for clinical trials. Further work to investigate component interactions is required and to validate the index in independent data sets.

Etiological research in pediatric multiple sclerosis: A tool to assess environmental exposures (PEDiatric Italian Genetic and enviRonment ExposurE Questionnaire)

Background

The etiology of pediatric-onset multiple sclerosis is unknown although putative genetic and environmental factors appear to be involved. Among children multiple sclerosis onset occurs closer to the susceptibility window thank in adults and the exposure to etiological environmental factors is more informative. An Italian multicentre case-control study (the PEDiatric Italian Genetic and enviRonment ExposurE, PEDIGREE study) was designed to investigate environmental exposures in pediatric-onset multiple sclerosis and their interaction with genetics.

Objectives

To collect evidence on exposures to environmental risk factors in pediatric-onset multiple sclerosis, a questionnaire was developed for the Italian population (PEDIGREE Questionnaire) and is presented.

Methods

PEDIGREE Questionnaire develops from an existing tool used in case-control studies on pediatric-onset multiple sclerosis in US Americans, and was translated, adapted and tested for the contents perceived relevance, acceptability, feasibility and reliability in a population of Italian pediatric subjects and their parents recruited from clinics and general population.

Results

PEDIGREE Questionnaire contents were overall deemed relevant by the study population, acceptable for 100% participants and feasible for at least 98%. PEDIGREE Questionnaire degree of reliability ranged 56% to 72%.

Conclusion

PEDIGREE Questionnaire proves to be an efficient tool to assess environmental exposures in the Italian pediatric population. We encourage the dissemination of population-specific questionnaires and shared methodology to optimize efforts in MS etiological research.

A proinflammatory diet is associated with an increased likelihood of first clinical diagnosis of central nervous system demyelination in women

BACKGROUND

While a number of studies have examined associations between dietary factors and risk of multiple sclerosis (MS), little is known about intakes of inflammation-modulating foods and nutrients and risk of MS.

OBJECTIVES

To test associations between the Dietary Inflammatory Index (DII®) and risk of a first clinical diagnosis of central nervous system (CNS) demyelination (FCD) (267 cases, 507 controls) using data from the Ausimmune Study.

METHODS

The 2003-2006 Ausimmune Study was a multicentre, matched, case-control study examining environmental risk factors for an FCD, a common precursor to MS. The DII is a well-recognised tool that categorises individuals' diets on a continuum from maximally anti-inflammatory to maximally pro-inflammatory. The DII score was calculated from dietary intake data collected using a food frequency questionnaire. Conditional logistic regression models were used to estimate the association between DII and FCD separately for men and women.

RESULTS

In women, a higher DII score was associated with increased likelihood of FCD, with a 17% increase in likelihood of FCD per one-unit increase in DII score (adjusted odds ratio 1.17, 95% confidence interval 1.04-1.33). There was no association between DII and FCD in men (adjusted odds ratio 0.88, 95% confidence interval 0.73-1.07).

CONCLUSIONS

These findings suggest that a pro-inflammatory diet is associated with an increased likelihood of FCD in women.

Omega-3 Index, fish consumption, use of fish oil supplements and first clinical diagnosis of central nervous system demyelination

Higher intakes of omega-3 polyunsaturated fatty acids (n3PUFAs) have been associated with lower MS risk. We aimed to test associations between the Omega-3 Index, blood levels of n3PUFAs, fish oil supplement use, and fish consumption with a first clinical diagnosis of CNS demyelination (FCD). Cases (n = 250) had a higher Omega-3 Index compared with a matched group of controls (n = 471) (average treatment effect (ATE)=0.31, p = 0.047, based on augmented inverse probability weighting). A higher percentage of cases than controls used fish oil supplements (cases=17% vs. controls=10%). We found that Omega-3 Index increased as time between FCD and study interview increased (e.g., at or below median (112 days), based on ATE, mean=5.30, 95% CI 5.08, 5.53; above median, mean=5.90, 95% CI 5.51, 6.30). Fish oil supplement use increased in a similar manner (at or below median (112 days), based on ATE, proportion=0.12, 95% CI 0.06, 0.18; above the median, proportion=0.21, 95% CI 0.14, 0.28). Our results suggest a behaviour change post FCD with increased use of fish oil supplements.

High Prudent diet factor score predicts lower relapse hazard in early multiple sclerosis

BACKGROUND

Dietary patterns and their association with subsequent clinical course have not been well studied in early multiple sclerosis (MS).

OBJECTIVES

To describe dietary patterns in people in 5 years following first clinical demyelination and assess associations with MS conversion and relapse.

METHODS

This study included baseline food frequency questionnaire dietary intake (entry to the Ausimmune Study) and 5-year follow-up; iterated principal factor analysis was applied. MS conversion and relapse risks were assessed by Cox proportional hazards models, adjusted for age, sex, study site, education, body mass index (BMI), smoking and omega-3 supplement use.

RESULTS

In cases with a first clinical diagnosis of central nervous system (CNS) demyelination, we identified three major dietary patterns, 'Prudent', 'High-Vegetable' and 'Mixed', explaining 43%, 37% and 24% of diet variance in dietary intake, respectively. Fruits, vegetables, fish, wholegrains and nuts loaded highly on the Prudent pattern, starchy vegetables and legumes on the High-Vegetable pattern, and meats and alcohol on the Mixed pattern. Diet factor scores were not associated with MS conversion risk. Those with baseline Prudent scores above the median had significantly lower relapse risk (adjusted hazard ratio = 0.54, 95% confidence interval (CI) 0.37, 0.81) with some evidence of a plateau effect.

CONCLUSION

Prudent diet factor score above the median was prospectively associated with lower relapse risk in the 5 years following the first clinical demyelinating event.

Childhood infections, vaccinations, and tonsillectomy and risk of first clinical diagnosis of CNS demyelination in the Ausimmune Study

BACKGROUND

The association between childhood vaccinations and infections and risk of multiple sclerosis is unclear; few studies have considered age at vaccination/infection.

OBJECTIVE

To explore age-related associations between childhood vaccinations, infection and tonsillectomy and risk of a first clinical diagnosis of CNS demyelination.

METHODS

Data on case (n = 275, 76.6% female; mean age 38.6 years) and age- and sex-matched control (n = 529) participants in an incident population-based case-control study included self-reported age at time of childhood vaccinations, infections, and tonsillectomy. Conditional logistic regression models were used to calculate adjusted odds ratios (AOR) and 95% confidence intervals (CI).

RESULTS

Poliomyelitis vaccination prior to school-age was associated with increased risk of a first clinical diagnosis of CNS demyelination (AOR = 2.60, 95%CI 1.02-6.68), based on a very small unvaccinated reference group. Late (11-15 years) rubella vaccination (compared to none) was associated with lower odds of being a case (AOR = 0.47, 95%CI 0.27-0.83). Past infectious mononucleosis at 11-15 years (AOR = 2.84, 95%CI 1.0-7.57) and 16-20 years (AOR = 1.92, 95%CI 1.12-3.27) or tonsillectomy in adolescence (11-15 years: AOR = 2.45, 95%CI 1.12-5.35), including after adjustment for IM, were associated with increased risk of a first clinical diagnosis of CNS demyelination.

CONCLUSIONS

Age at vaccination, infection or tonsillectomy may alter the risk of subsequent CNS demyelination. Failing to account for age effects may explain inconsistencies in past findings.

Effects of modified-release fampridine on upper limb impairment in patients with Multiple Sclerosis

BACKGROUND

Modified-release 4-aminopyridine (fampridine-MR) is used in the symptomatic treatment of walking disability in patients with multiple sclerosis (MS).  Its potential for use in other MS symptoms remains unproven and its mode of action in this context is uncertain. Interest is growing in the use of upper limb outcome measures in clinical trials in patients with Multiple Sclerosis, particularly in advanced or progressive disease.  This study tests the following hypotheses: (1) Fampridine-MR improves upper limb function in patients with MS and upper limb impairment.  (2) Treatment with fampridine-MR is associated with measurable alterations in objective electrophysiological parameters (evoked potentials and transcranial magnetic stimulation (TMS)) which may predict response to drug treatment.

METHODS

Study population: patients with MS of any disease subtype, duration and severity who have symptomatic impairment of one or both upper limbs.  A healthy control group was included for validation of clinical and electrophysiological measures.  Study design: randomised double blind placebo-controlled trial.  Treatment details: participants allocated to either fampridine-MR 10 mg bd or placebo of identical appearance for 8 weeks.  Primary outcome: performance on 9-hole peg test (9HPT) after 4 weeks.  Secondary outcomes: persistence of effect on 9HPT; grip strength; visual acuity and contrast sensitivity; modified fatigue impact scale score; sensory discrimination capacity; visual, somatosensory and motor evoked potentials; resting motor threshold; paired-pulse TMS; peripheral nerve conduction studies.

RESULTS

40 patients with MS (60% female, median age 52, median disease duration 13.5 years, median EDSS 6.0) were enrolled.  Treatment with fampridine-MR was not associated with any change in upper limb function as measured by the clinical primary or secondary outcomes.  Treatment with fampridine-MR was also not associated with any difference in electrophysiological measures of upper limb function.  This held true after adjustment for hand dominance, disease duration and severity.  Four patients withdrew from the trial because of lack of efficacy or side-effects; all were in the placebo arm.  Three patients were admitted to hospital during the study period; one with MS exacerbation (placebo group), one with syncope (drug group) and one with UTI (drug group); otherwise there were no serious adverse events.

CONCLUSION

Treatment with fampridine-MR was well-tolerated but did not produce clinical benefit in terms of upper limb function, vision or fatigue, nor was there any measurable effect on objective electrophysiological parameters.

Higher fish consumption and lower risk of central nervous system demyelination

BACKGROUND/OBJECTIVES

The evidence for diet as a risk factor for multiple sclerosis (MS) is inconclusive. We examined the associations between fish consumption and risk of a first clinical diagnosis of central nervous system demyelination (FCD), a common precursor to MS.

METHODS

The 2003-2006 Ausimmune Study was a case-control study examining environmental risk factors for FCD, with participants recruited from four regions of Australia and matched on age, sex, and study region. Dietary intake data were collected using a food frequency questionnaire. We used conditional logistic regression models to test associations between fish consumption (total, tinned, grilled, and fried) and risk of FCD (249 cases and 438 controls), adjusting for history of infectious mononucleosis, smoking, serum 25-hydroxyvitamin D concentrations, socio-economic status, omega-3 supplement use, dietary under-reporting, and total energy intake.

RESULTS

Higher total fish consumption (per 30 g/day, equivalent to two serves/week) was associated with an 18% reduced risk of FCD (AOR 0.82; 95% CI 0.70, 0.97). While we found no statistically significant associations between grilled and fried fish consumption and risk of FCD, higher tinned fish consumption (per 30 g/day) was associated with a 41% reduced risk of FCD (AOR 0.59; 95% CI 0.39, 0.89).

CONCLUSIONS

Tinned fish is predominantly oily, whereas grilled and fried fish are likely to be a combination of oily and white types. Oily fish is high in vitamin D and very long chain polyunsaturated omega-3 fatty acids, both of which may be beneficial in relation to MS.

A Higher Mediterranean Diet Score, Including Unprocessed Red Meat, Is Associated with Reduced Risk of Central Nervous System Demyelination in a Case-Control Study of Australian Adults

BACKGROUND

The evidence associating diet and risk of multiple sclerosis (MS) is inconclusive.

OBJECTIVES

The aim of this study was to investigate associations between a Mediterranean diet and risk of a first clinical diagnosis of central nervous system demyelination (FCD), a common precursor to MS.

METHODS

We used data from the 2003-2006 Ausimmune Study, an Australian multicenter, case-control study examining environmental risk factors for FCD, with participants matched on age, sex, and study region (282 cases, 558 controls; 18-59 y old; 78% female). The alternate Mediterranean diet score (aMED) was calculated based on data from a food-frequency questionnaire. We created a modified version of the aMED (aMED-Red) where ∼1 daily serving (65 g) of unprocessed red meat received 1 point. All other components remained the same as aMED. Conditional logistic regression (254 cases, 451 controls) was used to test associations between aMED and aMED-Red scores and categories and risk of FCD, adjusting for history of infectious mononucleosis, serum 25-hydroxyvitamin D concentrations, smoking, education, total energy intake, and dietary underreporting.

RESULTS

There was no statistically significant association between aMED and risk of FCD [per 1-SD increase in aMED score: adjusted odds ratio (aOR): 0.89; 95% CI: 0.75, 1.06; P = 0.181]. There was evidence of a nonlinear relation between aMED-Red and risk of FCD when a quadratic term was used (P = 0.016). Compared with the lowest category of aMED-Red, higher categories were significantly associated with reduced risk of FCD, corresponding to a 37% (aOR: 0.63; 95% CI: 0.41, 0.98; P = 0.039), 52% (aOR: 0.48; 95% CI: 0.28, 0.83; P = 0.009), and 42% (aOR: 0.58; 95% CI: 0.35, 0.96; P = 0.034) reduced risk of FCD in categories 2, 3, and 4, respectively.

CONCLUSIONS

A Mediterranean diet, including unprocessed red meat, was associated with reduced risk of FCD in this Australian adult population. The addition of unprocessed red meat to a Mediterranean diet may be beneficial for those at high risk of MS.

Higher Non-processed Red Meat Consumption Is Associated With a Reduced Risk of Central Nervous System Demyelination

The evidence associating red meat consumption and risk of multiple sclerosis is inconclusive. We tested associations between red meat consumption and risk of a first clinical diagnosis of central nervous system demyelination (FCD), often presaging a diagnosis of multiple sclerosis. We used food frequency questionnaire data from the 2003–2006 Ausimmune Study, an incident, matched, case-control study examining environmental risk factors for FCD. We calculated non-processed and processed red meat density (g/1,000 kcal/day). Conditional logistic regression models (with participants matched on age, sex, and study region) were used to estimate odds ratios (ORs), 95% confidence intervals (95% CI) and p-values for associations between non-processed (n = 689, 250 cases, 439 controls) and processed (n = 683, 248 cases, 435 controls) red meat density and risk of FCD. Models were adjusted for history of infectious mononucleosis, serum 25-hydroxyvitamin D concentrations, smoking, race, education, body mass index and dietary misreporting. A one standard deviation increase in non-processed red meat density (22 g/1,000 kcal/day) was associated with a 19% reduced risk of FCD (AOR = 0.81; 95%CI 0.68, 0.97; p = 0.02). When stratified by sex, higher non-processed red meat density (per 22 g/1,000 kcal/day) was associated with a 26% reduced risk of FCD in females (n = 519; AOR = 0.74; 95%CI 0.60, 0.92; p = 0.01). There was no statistically significant association between non-processed red meat density and risk of FCD in males (n = 170). We found no statistically significant association between processed red meat density and risk of FCD. Further investigation is warranted to understand the important components of a diet that includes non-processed red meat for lower FCD risk.

Low 25-Hydroxyvitamin D Concentration Is Not Associated With Refractive Error in Middle-Aged and Older Western Australian Adults

Purpose

To investigate the association between serum 25-hydroxyvitamin D (25[OH]D) concentration and refractive error in a community-based cohort of adults aged 46 to 69 years.

Methods

Residents of the City of Busselton in Western Australia born between 1946 and 1964 were invited to participate. Participants underwent cycloplegic autorefraction and completed questionnaires on education, occupational sun exposure, and physical activity. Blood samples were collected and serum frozen at −80°C. Serum 25[OH]D concentration was measured by immunoassay. Data on 25[OH]D were deseasonalized and multivariate models built to analyze the association between 25[OH]D concentration and spherical equivalent and myopia, defined as spherical equivalent <−0.50 D.

Results

After exclusions, data were available for 4112 participants. Serum 25[OH]D concentration was not associated with spherical equivalent or myopia after adjustment for confounding factors (β = −0.01, 95% confidence interval [CI]: −0.03 to −0.008, P = 0.25, and odds ratio = 1.02, 95% CI: 0.99 to 1.05, P = 0.12, respectively). When participants were classified into 25[OH]D groups of lower (<50 nmol/L), medium (≥50 to <75 nmol/L), and upper (≥75 nmol/L), the upper group had slightly greater myopic refractive error than the medium group (P = 0.02) but not the lower group, after adjustment for confounders.

Conclusions

There was no substantial association between 25[OH]D levels and spherical equivalent or odds of myopia in this study. The association previously noted between low serum 25[OH]D level and myopia in younger Western Australians is not evident in later adulthood.

Translational Relevance

This study provides further evidence suggesting that vitamin D levels are unrelated to myopia risk in adults and thus not a suitable target for myopia intervention.

A healthy dietary pattern associates with a lower risk of a first clinical diagnosis of central nervous system demyelination

BACKGROUND

The evidence associating diet and risk of multiple sclerosis is inconclusive.

OBJECTIVE

We investigated associations between dietary patterns and risk of a first clinical diagnosis of central nervous system demyelination, a common precursor to multiple sclerosis.

METHODS

We used data from the 2003-2006 Ausimmune Study, a case-control study examining environmental risk factors for a first clinical diagnosis of central nervous system demyelination, with participants matched on age, sex and study region. Using data from a food frequency questionnaire, dietary patterns were identified using principal component analysis. Conditional logistic regression models (n = 698, 252 cases, 446 controls) were adjusted for history of infectious mononucleosis, serum 25-hydroxyvitamin D concentrations, smoking, race, education, body mass index and dietary misreporting.

RESULTS

We identified two major dietary patterns - healthy (high in poultry, fish, eggs, vegetables, legumes) and Western (high in meat, full-fat dairy; low in wholegrains, nuts, fresh fruit, low-fat dairy), explaining 9.3% and 7.5% of variability in diet, respectively. A one-standard deviation increase in the healthy pattern score was associated with a 25% reduced risk of a first clinical diagnosis of central nervous system demyelination (adjusted odds ratio 0.75; 95% confidence interval 0.60, 0.94; p = 0.011). There was no statistically significant association between the Western dietary pattern and risk of a first clinical diagnosis of central nervous system demyelination.

CONCLUSION

Following healthy eating guidelines may be beneficial for those at high risk of multiple sclerosis.

Onset Symptoms, Tobacco Smoking, and Progressive-Onset Phenotype Are Associated With a Delayed Onset of Multiple Sclerosis, and Marijuana Use With an Earlier Onset

Background: Age at symptom onset (ASO) is a prognostic factor that could affect the accrual of disability in multiple sclerosis (MS) patients. Some factors are known to influence the risk of multiple sclerosis (MS), but their influence on the ASO is less well-investigated.

Objective: Examine the associations between known or emerging MS risk factors and ASO.

Methods: This was a multicenter study, incident cases (n = 279) with first clinical diagnosis of demyelinating event aged 18–59 years recruited at four Australian centres (latitudes 27°-43°S), from 1 November 2003 to 31 December 2006. Environmental/behavioral variables and initial symptoms were recorded at baseline interview. Linear regression was used to assess the association between risk factors and ASO.

Results: Five factors were significantly associated with ASO: a history of tobacco smoking was associated with 3.05-years later ASO (p = 0.002); a history of marijuana use was associated with 6.03-years earlier ASO (p < 0.001); progressive-onset cases had 5.61-years later ASO (p = 0.001); an initial presentation of bowel & bladder and cerebral dysfunctional were associated with 3.39 (p = 0.017) and 4.37-years (p = 0.006) later ASO, respectively. Other factors, including sex, offspring number, latitude of study site, history of infectious mononucleosis, HLA-DR15 & HLA-A2 genotype, 25(OH)D levels, and ultraviolet radiation exposure were not associated with ASO. Including all five significant variables into one model explained 12% of the total variance in ASO.

Conclusion: We found a novel association between a history of tobacco smoking and later onset, whereas marijuana use was associated with earlier onset. Behavioral factors seem important drivers of MS onset timing although much of the variance remains unexplained.

Reported Changes in Dietary Behavior Following a First Clinical Diagnosis of Central Nervous System Demyelination

Background/objectives

Although the current evidence is insufficient to recommend a special diet for people with multiple sclerosis (MS), dietary advice for people with MS is prolific online and in the media. This study aimed to describe dietary changes made in the year following a first clinical diagnosis of central nervous system demyelination (FCD), a common precursor to MS.

Subjects/methods

We used follow-up data from the Ausimmune Study, a multicentre matched case-control study examining the environmental risk factors for a FCD. A total of 244 cases (60 male, 184 female) completed a 1-year follow-up interview, which included a question about dietary changes. We described the number and proportion (%) of participants who reported making dietary changes and the type of change made. We investigated independent predictors of making a dietary change using a multivariable logistic regression model.

Results

A total of 38% (n = 92) of participants at the 1-year follow-up reported making at least one dietary change over the last year. There were no statistically significant independent associations between any participant characteristic and odds of making a dietary change. Of those who made at least one dietary change, the most common changes were increasing fruit and/or vegetable intake (27%, n = 25) and following a low-fat diet (25%, n = 23).

Conclusion

A considerable proportion of the study population reported making at least one dietary change in the year following a FCD, with the majority of changes being toward a healthier diet. Further research is warranted to investigate the reasons behind any dietary changes adopted by people with a FCD or with MS, and whether making a dietary change has benefits for the progression of demyelinating diseases, e.g., to a diagnosis of MS, as well as for general health and well-being.

Sun Exposure across the Life Course Significantly Modulates Early Multiple Sclerosis Clinical Course

Background

Low vitamin D and/or sun exposure have been associated with increased risk of multiple sclerosis (MS) onset. However, comparatively, few studies have prospectively examined associations between these factors and clinical course.

Objectives

To evaluate the association of sun exposure parameters and vitamin D levels with conversion to MS and relapse risk in a prospectively monitored cohort of 145 participants followed after a first demyelinating event up to 5-year review (AusLong Study).

Methods

Sun exposure prior to and after onset measured by annual questionnaire; ultraviolet radiation (UVR) "load" estimated by location of residence over the life course and ambient UVR levels. Serum 25-hydroxyvitamin D [25(OH)D] concentrations measured at baseline, 2/3-year, and 5-year review. MS conversion and relapse assessed by neurologist assessment and medical record review.

Results

Over two-thirds (69%) of those followed to 5-year review (100/145) converted to MS, with a total of 252 relapses. Higher pre-MS onset sun exposure was associated with reduced risk of MS conversion, with internal consistency between measures and dose-response relationships. Analogous associations were also seen with risk of relapse, albeit less strong. No consistent associations were observed between postonset sun exposure and clinical course, however. Notably, those who increased their sun exposure during follow-up had significantly reduced hazards of MS conversion and relapse. Serum 25(OH)D levels and vitamin D supplementation were not associated with conversion to MS or relapse hazard.

Conclusion

We found that preonset sun exposure was protective against subsequent conversion to MS and relapses. While consistent associations between postonset sun exposure or serum 25(OH)D level and clinical course were not evident, possibly masked by behavior change, those participants who markedly increased their sun exposure demonstrated a reduced MS conversion and relapse hazard, suggesting beneficial effects of sun exposure on clinical course.

Genetic variation in the gene LRP2 increases relapse risk in multiple sclerosis

BACKGROUND

Due to the lack of prospective studies with longitudinal data on relapse, past genetic studies have not attempted to identify genetic factors that predict relapse risk (the primary endpoint of many pivotal clinical trials testing the efficacy of multiple sclerosis (MS) disease-modifying drugs) at a genome-wide scale.

METHODS

We conducted a genome-wide association analysis (GWAS) to identify genetic variants that predict MS relapse risk, using a three-stage approach. First, GWAS was conducted using the southern Tasmania MS Longitudinal Study with 141 cases followed prospectively for a mean of 2.3 years. Second, GWAS was conducted using the Ausimmune Longitudinal Study with 127 cases having a classic first demyelinating event followed for 5 years from onset. Third, the top hits with p<5.0×10^-6 from the first two stages were combined with a longitudinal US paediatric MS cohort with 181 cases followed for 5 years after onset. Predictors of time to relapse were evaluated by a mixed effects Cox model. An inverse variance fixed effects model was then used to undertake a meta-analysis.

RESULTS

In the pooled results, using these three unique longitudinal MS cohorts, we discovered one novel locus (LRP2; most significant single nucleotide polymorphism rs12988804) that reached genome-wide significance in predicting relapse risk (HR=2.18, p=3.30×10^-8). LRP2 is expressed on the surface of many central nervous system cells including neurons and oligodendrocytes and is a critical receptor in axonal guidance.

CONCLUSIONS

The finding of a genetic locus that has extensive effects on neuronal development and repair is of interest as a potential modulator of MS disease course.

Environmental factors influencing multiple sclerosis in Latin America

It is generally accepted that autoimmune diseases like multiple sclerosis (MS) arise from complex interactions between genetic susceptibility and environmental factors. Genetic variants confer predisposition to develop MS, but cannot be therapeutically modified. On the other hand, several studies have shown that different lifestyle and environmental factors influence disease development, as well as activity levels and progression. Unlike genetic risk factors, these can be modified, with potential for prevention, particularly in high-risk populations. Most studies identifying particular lifestyle and environmental factors have been carried out in Caucasian patients with MS. Little or no data is available on the behavior of these factors in Latin American populations. Ethnic and geographic differences between Latin America and other world regions suggest potential regional variations in MS, at least with respect to some of these factors. Furthermore, particular environmental characteristics observed more frequently in Latin America could explain regional differences in MS prevalence. Site-specific studies exploring influences of local environmental factors are warranted.

An adverse lipid profile and increased levels of adiposity significantly predict clinical course after a first demyelinating event

OBJECTIVE

To investigate the prospective associations between adiposity and lipid-related variables and conversion to multiple sclerosis (MS), time to subsequent relapse and progression in disability.

METHODS

A cohort of 279 participants with a first clinical diagnosis of central nervous system demyelination was prospectively followed to 5-year review. Height, weight, waist and hip circumference were measured, and serum samples taken for measurement of lipids and apolipoproteins. Survival analysis was used for conversion to MS and time to relapse, and linear regression for annualised change in disability (Expanded Disability Status Scale).

RESULTS

Higher body mass index (BMI; adjusted HR (aHR): 1.22 (1.04 to 1.44) per 5 kg/m² increase), hip circumference (aHR: 1.32 (1.12 to 1.56) per 10 cm increase) and triglyceride levels (aHR: 1.20 (1.03 to 1.40) per unit increase) were associated with increased risk of subsequent relapse, while adiposity and lipid-related measures were not associated with conversion to MS. In addition, higher BMI (β: 0.04 (0.01 to 0.07) per 5 kg/m² increase), hip circumference (β: 0.04 (0.02 to 0.08) per 10 cm increase), waist circumference (β: 0.04 (0.02 to 0.07) per 10 cm increase), total cholesterol to high-density lipoprotein ratio (TC/HDL ratio; β: 0.05 (0.001 to 0.10) and non-HDL; β: 0.04 (0.001 to 0.08) at study entry) were associated with a higher subsequent annual change in disability.

CONCLUSIONS

Higher levels of adiposity, non-HDL and TC/HDL ratio were prospectively associated with a higher rate of disability progression, and higher adiposity and triglycerides were associated with relapse but not with conversion to MS. Improving the lipid profile and losing weight into the healthy range could reduce the accumulation of disability.

Variation within MBP gene predicts disease course in multiple sclerosis

OBJECTIVE

Prognosis following a first demyelinating event is difficult to predict, with no genetic markers of MS progression currently identified. Myelin basic protein (MBP) is a major component of the myelin sheath of CNS neurons and may play a central role in demyelinating diseases such as MS. However, genetic variation in MBP has not been implicated in MS onset risk in large genome-wide association studies. We hypothesized that genetic variations in MBP may be a determinant of MS clinical course.

MATERIALS AND METHODS

We investigated whether variations in the MBP gene altered clinical course (conversion to MS and/or relapse, and annualized change in disability), using a prospectively collected longitudinal cohort study of 127 persons who had had a first demyelinating event, followed up to the 5-year review.

RESULTS

We found one variant, rs12959006, predicted worse clinical outcomes. The risk genotype (CT + TT) was significantly associated with hazard of relapse (HR = 1.74, 95% CI = 1.19-2.56, p = .005) and of greater annualized disability progression (β = 0.18, 95% CI = 0.06-0.30, p = .004). We also found a significant interaction between the risk genotype and baseline anti-HHV6 IgG in predicting MS (p_interaction = 0.05) and relapse (p_interaction = 0.02). Functional prediction analysis showed this variant is the target of many transcription factors and the binding sites of miR-218 and miR-188-3p.

CONCLUSIONS

Our results provide novel insights into the role of genetic variation within the MBP gene predicting MS clinical course, both directly and by interaction with known environmental MS risk factors.

Population attributable fractions and joint effects of key risk factors for multiple sclerosis

AIM

We examined the combined effect of having multiple key risk factors and the interactions between the key risk factors of multiple sclerosis (MS).

METHODS

We performed an incident case-control study including cases with a first clinical diagnosis of central nervous system demyelination (FCD) and population-based controls.

RESULTS

Compared to those without any risk factors, those with one, two, three, and four or five risk factors had increased odds of being an FCD case of 2.12 (95% confidence interval (CI), 1.11-4.03), 4.31 (95% CI, 2.24-8.31), 7.96 (95% CI, 3.84-16.49), and 21.24 (95% CI, 5.48-82.40), respectively. Only HLA-DR15 and history of infectious mononucleosis interacted significantly on the additive scale (Synergy index, 3.78; p = 0.03). The five key risk factors jointly accounted for 63.8% (95% CI, 43.9-91.4) of FCD onset. High anti-EBNA IgG was another important contributor.

CONCLUSIONS

A high proportion of FCD onset can be explained by the currently known risk factors, with HLA-DR15, ever smoking and low cumulative sun exposure explaining most. We identified a significant interaction between HLA-DR15 and history of IM in predicting an FCD of CNS demyelination, which together with previous observations suggests that this is a true interaction.

Analytical Bias in the Measurement of Serum 25-Hydroxyvitamin D Concentrations Impairs Assessment of Vitamin D Status in Clinical and Research Settings

Measured serum 25-hydroxyvitamin D concentrations vary depending on the type of assay used and the specific laboratory undertaking the analysis, impairing the accurate assessment of vitamin D status. We investigated differences in serum 25-hydroxyvitamin D concentrations measured at three laboratories (laboratories A and B using an assay based on liquid chromatography-tandem mass spectrometry and laboratory C using a DiaSorin Liaison assay), against a laboratory using an assay based on liquid chromatography-tandem mass spectrometry that is certified to the standard reference method developed by the National Institute of Standards and Technology and Ghent University (referred to as the 'certified laboratory'). Separate aliquots from the same original serum sample for a subset of 50 participants from the Ausimmune Study were analysed at the four laboratories. Bland-Altman plots were used to visually check agreement between each laboratory against the certified laboratory. Compared with the certified laboratory, serum 25-hydroxyvitamin D concentrations were on average 12.4 nmol/L higher at laboratory A (95% limits of agreement: -17.8,42.6); 12.8 nmol/L higher at laboratory B (95% limits of agreement: 0.8,24.8); and 10.6 nmol/L lower at laboratory C (95% limits of agreement: -48.4,27.1). The prevalence of vitamin D deficiency (defined here as 25-hydroxyvitamin D <50 nmol/L) was 24%, 16%, 12% and 41% at the certified laboratory, and laboratories A, B, and C, respectively. Our results demonstrate considerable differences in the measurement of 25-hydroxyvitamin D concentrations compared with a certified laboratory, even between laboratories using assays based on liquid chromatography-tandem mass spectrometry, which is often considered the gold-standard assay. To ensure accurate and reliable measurement of serum 25-hydroxyvitamin D concentrations, all laboratories should use an accuracy-based quality assurance system and, ideally, comply with international standardisation efforts.

Serum phosphorylated neurofilament-heavy chain levels in multiple sclerosis patients

OBJECTIVES

We evaluated whether the measurement of serum phosphorylated neurofilament heavy chain (pNF-H) titre is likely to be a valid biomarker of axonal injury in multiple sclerosis (MS).

METHODS

Serum pNF-H concentrations were measured by ELISA in cases with relapsing-remitting (RR)-MS (n=81), secondary progressive (SP) MS (n=13) and primary progressive (PP)-MS; n=6) MS; first demyelinating event (FDE; n=82); and unaffected controls (n=135). A subset of MS cases (n=45) were re-sampled on one or multiple occasions. The Multiple Sclerosis Severity Score (MSSS) and MRI measures were used to evaluate associations between serum pNF-H status, disease severity and cerebral lesion load and activity.

RESULTS

We confirmed the presence of pNF-H peptides in serum by ELISA. We showed that a high serum pNF-H titre was detectable in 9% of RR-MS and FDE cases, and 38.5% of SP-MS cases. Patients with a high serum pNF-H titre had higher average MSSS scores and T2 lesion volumes than patients with a low serum pNF-H titre. Repeated sampling of a subset of MS cases showed that pNF-H levels can fluctuate over time, likely reflecting temporal dynamics of axonal injury in MS.

CONCLUSIONS

A subset of FDE/MS cases was found to have a high serum pNF-H titre, and this was associated with changes in clinical outcome measures. We propose that routine measurement of serum pNF-H should be further investigated for monitoring axonal injury in MS.

UV and dietary predictors of serum 25-hydroxyvitamin D concentrations among young shift-working nurses and implications for bone density and skin cancer

OBJECTIVE

In 2011, the U.S. Institute of Medicine updated the definition of vitamin D inadequacy to serum 25-hydroxyvitamin D (25(OH)D) concentration of 30-<50 nmol/l and of deficiency to serum 25(OH)D < 30 nmol/l. We describe the prevalence of these conditions according to these definitions, seasonal variation in 25(OH)D and predictors of serum 25(OH)D concentrations among working, white women.

DESIGN

Participants recorded lifestyle factors and dietary intake and provided fasting blood samples for measurement of serum 25(OH)D in both summer and winter. Predictors of serum 25(OH)D variation were analysed using linear regression and generalized linear mixed models.

SETTING

Kingston General Hospital in Kingston, Ontario, Canada, from April 2008 to July 2009.

SUBJECTS

Female premenopausal nurses (n 83) working full-time rotating shifts.

RESULTS

Deficient or inadequate vitamin D status was observed in 9% of participants following summer/autumn and in 13% following winter/spring. Predictors of serum 25(OH)D concentration were vitamin D supplement use, tanning bed use and season. Tanning bed use increased serum 25(OH)D by 23.24 nmol/l (95% CI 8.78, 37.69 nmol/l, P = 0.002) on average.

CONCLUSIONS

According to the 2011 Institute of Medicine bone health guidelines, over 10% of nurses had deficient or inadequate vitamin D status following winter. Higher serum concentrations were associated with use of tanning beds and vitamin D supplements. As health promotion campaigns and legal restrictions are successful in reducing tanning bed use among women, our data suggest that increased prevalence of vitamin D inadequacy and deficiency may be a consequence, and that low vitamin D status will need to be countered with supplementation.

A novel approach for prediction of vitamin d status using support vector regression

BACKGROUND

Epidemiological evidence suggests that vitamin D deficiency is linked to various chronic diseases. However direct measurement of serum 25-hydroxyvitamin D (25(OH)D) concentration, the accepted biomarker of vitamin D status, may not be feasible in large epidemiological studies. An alternative approach is to estimate vitamin D status using a predictive model based on parameters derived from questionnaire data. In previous studies, models developed using Multiple Linear Regression (MLR) have explained a limited proportion of the variance and predicted values have correlated only modestly with measured values. Here, a new modelling approach, nonlinear radial basis function support vector regression (RBF SVR), was used in prediction of serum 25(OH)D concentration. Predicted scores were compared with those from a MLR model.

METHODS

Determinants of serum 25(OH)D in Caucasian adults (n = 494) that had been previously identified were modelled using MLR and RBF SVR to develop a 25(OH)D prediction score and then validated in an independent dataset. The correlation between actual and predicted serum 25(OH)D concentrations was analysed with a Pearson correlation coefficient.

RESULTS

Better correlation was observed between predicted scores and measured 25(OH)D concentrations using the RBF SVR model in comparison with MLR (Pearson correlation coefficient: 0.74 for RBF SVR; 0.51 for MLR). The RBF SVR model was more accurately able to identify individuals with lower 25(OH)D levels (<75 nmol/L).

CONCLUSION

Using identical determinants, the RBF SVR model provided improved prediction of serum 25(OH)D concentrations and vitamin D deficiency compared with a MLR model, in this dataset.

Adherence to MRI protocol consensus guidelines in multiple sclerosis: an Australian multi-centre study

INTRODUCTION

Multiple sclerosis (MS) is a debilitating disease that causes significant morbidity within a young demographic. Diagnostic guidelines for MS have evolved, and imaging has played an increasingly important role in diagnosis over the last two decades. For imaging to contribute to diagnosis in a meaningful way, it must be reproducible. Consensus guidelines for MRI in MS exist to define correct sequence type and imaging technique, but it is not clear to what extent they are followed. This study reviewed MRI studies performed on Australian individuals presenting with a first clinical diagnosis of central nervous system demyelination (FCD) for adherence to published guidelines and discussed practical implementation of MS guidelines in light of recent updates.

METHODS

The Ausimmune study was a prospective case control study of Australian participants presenting with FCD from 2003 to 2006. Baseline cranial and spinal cord MRI studies of 226 case participants from four separate Australian regions were reviewed. MRI sequences were classified according to anatomical location, slice plane, tissue weighting and use of gadolinium-containing contrast media. Results were compared with the 2003 Consortium of Multiple Sclerosis Centres MRI protocol for the diagnosis of MS.

RESULTS

The composition of core cranial MRI sequences performed varied across the 226 scans. Of the studies, 91% included sagittal fluid attenuated inversion recovery (FLAIR) sequences. Cranial axial T2-weighted, axial FLAIR and axial proton density-weighted sequences were performed in 88%, 60% and 16% (respectively) of scans. Only 25% of the studies included a T1-weighted contrast-enhanced sequence. Concordance with the guidelines in all sequences was very low (2).

CONCLUSION

Only a small number of MRI investigations performed included all of the sequences stipulated by consensus guidelines. This is likely due to poor awareness in the imaging community of the guidelines and the rationale behind certain sequences. Radiologists with a sub-speciality interest in neuroradiology should take ownership of this issue and ensure that recommended imaging guidelines are followed.

Vitamin D status: multifactorial contribution of environment, genes and other factors in healthy Australian adults across a latitude gradient

Vitamin D deficiency is common and implicated in risk of several human diseases. Evidence on the relative quantitative contribution of environmental, genetic and phenotypic factors to vitamin D status (assessed by the serum concentration of 25-hydroxyvitamin D, 25(OH)D) in free-living populations is sparse. We conducted a cross-sectional study of 494 Caucasian adults aged 18-61years, randomly selected from the Australian Electoral Roll according to groups defined by age, sex and region (spanning 27°-43°South). Data collected included personal characteristics, sun exposure behaviour, biomarkers of skin type and past sun exposure, serum 25(OH)D concentration and candidate single nucleotide polymorphisms. Ambient ultraviolet radiation (UVR) levels in the month six weeks before blood sampling best predicted vitamin D status. Serum 25(OH)D concentration increased by 10nmol/L as reported time in the sun doubled. Overall, 54% of the variation in serum 25(OH)D concentration could be accounted for: 36% of the variation was explained by sun exposure-related factors; 14% by genetic factors (including epistasis) and 3.5% by direct measures of skin phenotype. Novel findings from this study are demonstration of gene epistasis, and quantification of the relative contribution of a wide range of environmental, constitutional and genetic factors to vitamin D status. Ambient UVR levels and time in the sun were of prime importance but it is nonetheless important to include the contribution of genetic factors when considering sun exposure effects. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Early-life hygiene-related factors affect risk of central nervous system demyelination and asthma differentially

The increasing prevalence of immune-related diseases, including multiple sclerosis, may be partly explained by reduced microbial burden during childhood. Within a multi-centre case-control study population, we examined: (i) the co-morbid immune diseases profile of adults with a first clinical diagnosis of central nervous system demyelination (FCD) and (ii) sibship structure in relation to an autoimmune (FCD) and an allergic (asthma) disease. FCD cases (n = 282) were aged 18-59 years; controls (n = 558) were matched on age, sex and region. Measures include: history of doctor-diagnosed asthma; sibling profile (number; dates of birth); and regular childcare attendance. FCD cases did not differ from controls with regard to personal or family history of allergy, but had a greater likelihood of chronic fatigue syndrome [odds ratio (OR) = 3·11; 95% confidence interval (CI) 1·11, 8·71]. Having any younger siblings showed reduced odds of FCD (OR = 0·68; 95% CI: 0·49, 0·95) but not asthma (OR = 1·47; 95% CI: 0·91, 2·38). In contrast, an increasing number of older siblings was associated with reduced risk of asthma (P trend = 0·04) but not FCD (P trend = 0·66). Allergies were not over-represented among people presenting with FCD. Sibship characteristics influence both FCD and asthma risk but the underlying mechanisms differ, possibly due to the timing of the putative 'sibling effect'.

The physical anthropometry, lifestyle habits and blood pressure of people presenting with a first clinical demyelinating event compared to controls: The Ausimmune study

Introduction:

Lifestyle factors prior to a first clinical demyelinating event (FCD), a disorder often preceding the development of clinically definite multiple sclerosis (MS), have not previously been examined in detail. Past tobacco smoking has been consistently associated with MS.

Methods:

This was a multicentre incident case-control study. Cases ( n = 282) were aged 18–59 years with an FCD and resident within one of four Australian centres (from latitudes 27°S to 43°S), from 1 November 2003 to 31 December 2006. Controls ( n = 558) were matched to cases on age, sex and study region, without CNS demyelination. Exposures measured included current and past tobacco and marijuana, alcohol and beverage use, physical activity patterns, blood pressure and physical anthropometry.

Results:

A history of smoking ever was associated with FCD risk (AOR 1.89 (95%CL 1.82, 3.52)). Marijuana use was not associated with FCD risk after adjusting for confounders such as smoking ever but the estimates were imprecise because of a low prevalence of use. Alcohol consumption was common and not associated with FCD risk. No case-control differences in blood pressure or physical anthropometry were observed.

Conclusions:

Past tobacco smoking was positively associated with a risk of FCD but most other lifestyle factors were not. Prevention efforts against type 2 diabetes and cardiovascular disease by increasing physical activity and reducing obesity are unlikely to alter MS incidence, and more targeted campaigns will be required.

Occupational exposure and risk of central nervous system demyelination

Inconsistent evidence exists regarding the association between work-related factors and risk of multiple sclerosis (MS). We examined the association between occupational exposures and risk of a first clinical diagnosis of central nervous system demyelination (FCD), which is strongly associated with progression to MS, in a matched case-control study of 276 FCD cases and 538 controls conducted in Australia (2003-2006). Using a personal residence and work calendar, information on occupational history and exposure to chemicals and animals was collected through face-to-face interviews. Few case-control differences were noted. Fewer cases had worked as professionals (≥6 years) than controls (adjusted odds ratio (AOR) = 0.60, 95% confidence interval (CI): 0.37, 0.96). After further adjustment for number of children, cases were more likely to have ever been exposed to livestock than controls (AOR = 1.54, 95% CI: 1.03, 2.29). Among women, there was an increase in FCD risk associated with 10 or more years of exposure to livestock (AOR = 2.78, 95% CI: 1.22, 6.33) or 6 or more years of farming (AOR = 2.00, 95% CI: 1.23, 3.25; also adjusted for number of children). Similar findings were not evident among men. Thus, farming and exposure to livestock may be important factors in the development of FCD among women, with this finding further revealed after the confounding effect of parity or number of children is considered.

Design, methodological issues and participation in a multiple sclerosis case-control study

OBJECTIVES

This study was conducted to determine whether the risk of developing multiple sclerosis (MS) was associated with certain environmental exposures or genetic factors previously reported to influence MS risk. This paper describes the methodological issues, study design and characteristics of the study population.

MATERIALS AND METHODS

Individuals with definite MS were identified from a prevalence study conducted in three geographic areas. The target number of cases was not reached, so an additional study area was added. Identifying clinic controls was inefficient, so controls were recruited using random digit dialing. All study participants completed a detailed questionnaire regarding environmental exposures using computer-assisted telephone interviewing, and blood was collected for genetic analysis.

RESULTS

In total, 276 cases and 590 controls participated, but participation rates were low, ranging from 28.4% to 38.9%. Only one-third (33.6%) of individuals identified in the prevalence study agreed to participate in the case-control study. Cases were more likely to be non-Hispanic white and older than their source populations as identified in the preceding prevalence study (P < 0.05). Most participants provided a blood sample for genotyping (91%; n = 789).

CONCLUSIONS

Epidemiological studies play a key role in identifying genetic and environmental factors that are associated with complex diseases like MS. Methodological issues arise in every study, and investigators need to be able to detect, respond to and correct problems in a timely and scientifically valid manner.

Sunlight exposure and sun sensitivity associated with disability progression in multiple sclerosis

BACKGROUND

Sunlight and vitamin D have been inversely associated with the risk of multiple sclerosis (MS).

OBJECTIVE

We investigated sunlight exposure and sun sensitivity in relation to disability progression in MS.

METHODS

We conducted a survey among persons with MS, registered by the Flemish MS society, Belgium, and stratified data according to relapsing-onset and progressive-onset MS. We used Kaplan-Meier survival and Cox proportional hazard regression analyses with time to Expanded Disability Status Scale (EDSS) 6 as outcome measure. Hazard ratios for the time from onset and from birth were calculated for the potentially predictive variables, adjusting for age at onset, gender and immunomodulatory treatment.

RESULTS

704 (51.3%) of the 1372 respondents had reached EDSS 6. In relapsing-onset MS, respondents reporting equal or higher levels of sun exposure than persons of the same age in the last 10 years had a decreased risk of reaching EDSS 6. In progressive-onset MS, increased sun sensitivity was associated with an increased hazard of reaching EDSS 6.

CONCLUSION

The association of higher sun exposure with a better outcome in relapsing-onset MS may be explained by either a protective effect or reverse causality. Mechanisms underlying sun sensitivity might influence progression in progressive-onset MS.