[show abstract][hide abstract] ABSTRACT: Using the ImmunoChip custom genotyping array, we analyzed 14,498 subjects with multiple sclerosis and 24,091 healthy controls for 161,311 autosomal variants and identified 135 potentially associated regions (P < 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 subjects with multiple sclerosis and 26,703 healthy controls. In these 80,094 individuals of European ancestry, we identified 48 new susceptibility variants (P < 5.0 × 10(-8)), 3 of which we found after conditioning on previously identified variants. Thus, there are now 110 established multiple sclerosis risk variants at 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 catalog of multiple sclerosis risk variants and illustrates the value of fine mapping in the resolution of GWAS signals.
[show abstract][hide abstract] ABSTRACT: 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.
[show abstract][hide abstract] ABSTRACT: 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 18-61 years, 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.
The Journal of steroid biochemistry and molecular biology 02/2013; · 2.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: This article describes the rationale, methodology and major findings of the Tasmanian Multiple Sclerosis Longitudinal (MSL) Study, a prospective cohort studying seeking to evaluate the behavioural, environmental and genetic factors associated with the clinical course of established multiple sclerosis. Originally developed to evaluate the previously demonstrated association between personal sun exposure and vitamin D with relapse and disability progression using a prospective cohort design, the MSL study has since produced a large of scientific output, not least its demonstration of an inverse association between serum vitamin D and subsequent relapse risk, but also evidence that the interferon-beta medication exerts its effects in MS via vitamin D, and found links between human herpesvirus 6 exposure and relapse risk, cigarette smoking and disability progression, sun exposure and fatigue and depression, and modulating effects of PRKC alleles and relapse risk in MS.
[show abstract][hide abstract] ABSTRACT: Multiple sclerosis (MS) is a chronic disabling disease of the central nervous system commonly affecting young adults. Pathologically, there are patches of inflammation (plaques) with demyelination of axons and oligodendrocyte loss. There is a global latitude gradient in MS prevalence, and incidence of MS is increasing (particularly in females). These changes suggest a major role for environmental factors in causation of disease. We have reviewed the evidence and potential mechanisms of action for three exposures: vitamin D, Epstein Barr virus and cigarette smoking. Recent advances supporting gene-environment interactions are reviewed. Further research is needed to establish mechanisms of causality in humans and to explore preventative strategies.
International Journal of Molecular Sciences 01/2012; 13(9):11718-52. · 2.46 Impact Factor
[show abstract][hide abstract] ABSTRACT: Some of the strongest associations with MS onset are for human herpesviruses, particularly Epstein-Barr virus (EBV) and human herpesvirus 6 (HHV-6). Their role in MS clinical course is less clear, however.
Prospective cohort of 198 persons with clinically definite MS, followed 2002-5, and serum samples obtained from all subjects at study entry to measure anti-HHV-6 and anti-EBV (Epstein-Barr nuclear antigen [EBNA] and viral capsid antigen [VCA]) IgG titers. Association with relapse evaluated using survival analysis; association with disability/progression evaluated using linear regression or multilevel mixed-effects linear regression.
For the 145 persons with relapsing-remitting MS followed beyond one review, anti-HHV-6 IgG titer was positively associated with the hazard of relapse with a dose-dependent trend (p = 0.003), not affected by adjustment for anti-EBV IgG titers, neither of which were independently associated with relapse. There was no significant association between anti-human herpesvirus IgG titers and baseline-measured disability scores, or change in disability scores; however, anti-HHV-6 IgG titers were 2.8 times higher among progressive-course females than progressive-course males.
These findings suggest that, in addition to a potential etiological role in MS, HHV-6 infection or the immune response to HHV-6 antigens may have an effect on the risk of MS relapses and possibly on progressive courses of MS. The observed effect was directly related to anti-HHV-6 IgG titers and may indicate that either HHV-6 infection or factors associated with an altered humoral immune response to HHV-6 may have an effect on MS clinical course. Anti-HHV-6 IgG titer may be a useful prognostic factor in relapsing-remitting MS clinical course.
[show abstract][hide abstract] ABSTRACT: Multiple sclerosis is a common disease of the central nervous system in which the interplay between inflammatory and neurodegenerative processes typically results in intermittent neurological disturbance followed by progressive accumulation of disability. Epidemiological studies have shown that genetic factors are primarily responsible for the substantially increased frequency of the disease seen in the relatives of affected individuals, and systematic attempts to identify linkage in multiplex families have confirmed that variation within the major histocompatibility complex (MHC) exerts the greatest individual effect on risk. Modestly powered genome-wide association studies (GWAS) have enabled more than 20 additional risk loci to be identified and have shown that multiple variants exerting modest individual effects have a key role in disease susceptibility. Most of the genetic architecture underlying susceptibility to the disease remains to be defined and is anticipated to require the analysis of sample sizes that are beyond the numbers currently available to individual research groups. In a collaborative GWAS involving 9,772 cases of European descent collected by 23 research groups working in 15 different countries, we have replicated almost all of the previously suggested associations and identified at least a further 29 novel susceptibility loci. Within the MHC we have refined the identity of the HLA-DRB1 risk alleles and confirmed that variation in the HLA-A gene underlies the independent protective effect attributable to the class I region. Immunologically relevant genes are significantly overrepresented among those mapping close to the identified loci and particularly implicate T-helper-cell differentiation in the pathogenesis of multiple sclerosis.
[show abstract][hide abstract] ABSTRACT: There is a striking latitudinal gradient in multiple sclerosis (MS) prevalence, but exceptions in Mediterranean Europe and northern Scandinavia, and some systematic reviews, have suggested that the gradient may be an artefact. The authors sought to evaluate the association between MS prevalence and latitude by meta-regression.
Studies were sourced from online databases, reference mining and author referral. Prevalence estimates were age-standardised to the 2009 European population. Analyses were carried out by means of random-effects meta-regression, weighted with the inverse of within-study variance. The authors included 650 prevalence estimates from 321 peer-reviewed studies; 239 were age-standardised, and 159 provided sex-specific data. The authors found a significant positive association (change in prevalence per degree-latitude) between age-standardised prevalence (1.04, p<0.001) and latitude that diminished at high latitudes. Adjustment for prevalence year strengthened the association with latitude (2.60, p<0.001). An inverse gradient in the Italian region reversed on adjustment for MS-associated HLA-DRB1 allele distributions. Adjustment for HLA-DRB1 allele frequencies did not appreciably alter the gradient in Europe. Adjustment for some potential sources of bias did not affect the observed associations.
This, the most comprehensive review of MS prevalence to date, has confirmed a statistically significant positive association between MS prevalence and latitude globally. Exceptions to the gradient in the Italian region and northern Scandinavia are likely a result of genetic and behavioural-cultural variations. The persistence of a positive gradient in Europe after adjustment for HLA-DRB1 allele frequencies strongly supports a role for environmental factors which vary with latitude, the most prominent candidates being ultraviolet radiation (UVR)/vitamin D.
Journal of neurology, neurosurgery, and psychiatry 04/2011; 82(10):1132-41. · 4.87 Impact Factor
[show abstract][hide abstract] ABSTRACT: Hobart, Tasmania, has been the site of two major studies of multiple sclerosis (MS) frequency, in 1951-1961 and 1971-1981. Since then, there have been no studies of MS frequency in Hobart.
Using a prevalent cohort of 226 cases in 2001 and 265 in 2009, the authors undertook a two-stage survey of MS frequency in Hobart. Combined with the published data from the two preceding studies, the authors conducted a time-trend analysis of MS epidemiology over 1951-2009.
The age-standardised prevalence in 2001 was 96.6/100 000, and 99.6/100 000 in 2009, a significant increase from the 1961 prevalence of 32.5/100 000 (p<0.001). Female prevalence increased over each time point; male prevalence increased between 1961 and 2001 but was unchanged thereafter. Incidence over 2001-2009 was 3.7/100 000, significantly increased from the 1951-1961 incidence of 2.2/100 000 (p=0.004), though the majority of this was between 1951-1961 and 1971-1981. Mortality fell by half from 2.4/100 000 in 1951-1959 to 1.0/100 000 in 2001-2009-this decreased mortality and an older cohort contribute to the increase in prevalence. Neither prevalence (p=0.48) nor incidence (p=0.18) sex ratios changed significantly between 1951 and 2009.
Between 1951 and 2009, the age-standardised prevalence of MS in Hobart increased threefold, and the incidence nearly doubled. Part of the increase in prevalence was due to an increased longevity, decreased mortality and increased incidence. Differences in patterns by birthplace may be explained by the Australian assisted-migration programme of 1945-1981. These data do not demonstrate the strong and significant changes in sex ratio observed elsewhere.
Journal of neurology, neurosurgery, and psychiatry 02/2011; 82(2):180-7. · 4.87 Impact Factor
[show abstract][hide abstract] ABSTRACT: A protective association between higher vitamin D levels and the onset of multiple sclerosis (MS) has been demonstrated; however, its role in modulating MS clinical course has been little studied. We investigated whether higher levels of serum 25-hydroxyvitamin D (25-OH-D) were associated with a lower risk of relapses in people with MS.
We conducted a prospective cohort study of 145 participants with relapsing-remitting MS from 2002 to 2005. Serum 25-OH-D levels were measured biannually, and the hazard of relapse was assessed using survival analysis.
There was an inverse linear relationship between 25-OH-D levels and the hazard of relapse over the subsequent 6 months, with hazard ratio (HR) 0.91 (95% confidence interval [CI]: 0.85-0.97) per 10 nmol/l increase in 25-OH-D level (p = 0.006). When variation due to timing of blood collection was removed by estimating 25-OH-D at the start of each season, this association persisted, with HR 0.90 (95% CI, 0.83-0.98) per 10 nmol/l increase (p = 0.016). Taking into account the biological half-life of 25-OH-D, we estimated 25-OH-D at monthly intervals, resulting in a slightly enhanced association, with HR 0.88 (95% CI, 0.82-0.95) per 10 nmol/l increase (p = 0.001). Adjusting for potential confounders did not alter these findings.
In this prospective population-based cohort study, in a cohort largely on immunomodulatory therapy, higher 25-OH-D levels were associated with a reduced hazard of relapse. This occurred in a dose-dependent linear fashion, with each 10 nmol/l increase in 25-OH-D resulting in up to a 12% reduction in risk of relapse. Clinically, raising 25-OH-D levels by 50 nmol/l could halve the hazard of a relapse.
Annals of Neurology 08/2010; 68(2):193-203. · 11.19 Impact Factor
[show abstract][hide abstract] ABSTRACT: Demyelinating acute transverse myelitis may be the first presentation of multiple sclerosis or remain a clinically isolated syndrome. North Canterbury, New Zealand provides a well circumscribed population to study acute transverse myelitis. Objective: to identify prognostic features, clinical outcomes and incidence of ATM in North Canterbury, New Zealand. All patients with acute transverse myelitis as a first neurological presentation diagnosed from January 2001 to December 2005 at a single institution providing all neurological care for North Canterbury were assessed for clinical data, MRI findings, cerebrospinal fluid results and clinical outcomes. CHAMPS, Barkhof/Tintore and Swanton criteria were applied to brain MRI. Sixty-one patients were identified with a mean duration of follow-up of 30 +/- 17 months. Fifty percent of patients with ATM with brain lesions by CHAMPS criteria converted to clinically definite multiple sclerosis. No patients with idiopathic acute transverse myelitis converted to clinically definite multiple sclerosis. There was a strong association with conversion to clinically definite multiple sclerosis and abnormal brain MRI by CHAMPS criteria (hazard ratio, 5.63; 1.83-17.3), Barkhof/Tintore criteria (hazard ratio, 6.43; 2.31-17.9) and Swanton criteria (hazard ratio, 4.53; 1.67-12.3). The age standardized annual incidence of acute transverse myelitis was 24.6 (18.2-31.1) per million, of definite and possible idiopathic acute transverse myelitis was 6.2 (2.9-9.6) per million, and of acute transverse myelitis with brain lesions was 4.7 (1.9-7.6) per million. Patients with idiopathic acute transverse myelitis are at low risk for conversion to clinically definite multiple sclerosis. Abnormal brain MRI by CHAMPS criteria is a sensitive predictor of conversion to clinically definite multiple sclerosis. The annual incidence of acute transverse multiple sclerosis in North Canterbury, New Zealand is significantly higher than previously reported.