Season of birth is associated with multiple sclerosis and disease severity.

BACKGROUND: The latitude gradient in multiple sclerosis incidence indicates that low sun exposure and therefore vitamin D deficiency is associated with multiple sclerosis risk. OBJECTIVE: Investigation of the effect of month of birth, which influences postnatal vitamin D levels, on multiple sclerosis risk and severity in Sweden. METHODS: Patients and population-based controls were included from three nationwide cohorts. Differences in month of birth between cases and controls were analyzed using logistic regression and examined for effect modification by calendar year and geographic region at birth. RESULTS: Males had a reduced risk of multiple sclerosis if born in the winter and increased risk if born in the early fall. Individuals born before 1960 had an increased risk if born in summer or fall. Being born in late summer and early fall was associated with more severe disease. CONCLUSIONS: We identified a birth cohort effect on the association between the month of birth and multiple sclerosis, with a more significant effects for births before 1960. This coincides with a period of lower breastfeeding rates, recommended intake of vitamin D, and sun exposure, resulting in a lower vitamin D exposure during the fall/winter season for infants born in the summer.

Stressful life events are associated with the risk of multiple sclerosis.

BACKGROUND AND PURPOSE: Unexpected stressful life events may alter immune function and affect susceptibility to autoimmune diseases including multiple sclerosis (MS). Current results from epidemiological investigations examining the role of stress in MS remain inconsistent. The aim was to conduct the hitherto largest population-based case-control study on this topic. METHODS: Extensive questionnaire information collected on lifestyle environmental factors available for 2930 incident MS cases and 6170 controls were used to assess the association of 10 major life events that had occurred before disease onset with the risk of MS by unconditional logistic regressions, adjusting for potential confounders. Stratified analyses were also performed by sex and time. RESULTS: Compelling evidence was found for a link between major life events and risk of MS - most events significantly increased disease risk by 17%-30%. It was further observed that women were affected to a greater extent than men under certain stressful scenarios, and that most events that happened recently (≤5 years prior to MS onset) had significant effects on MS, indicating a critical window in disease development. CONCLUSION: Stressful life events may have an adverse effect on the risk of MS. Research into the mechanisms of this observation may give important clues to triggering pathogenetic events in MS.

Clinical course of multiple sclerosis and labour-force absenteeism: a longitudinal population-based study.

BACKGROUND AND PURPOSE: Multiple sclerosis (MS) is a chronic neurological disease associated with substantial disability and morbidity. The objective of our study was to assess the long-term consequences of MS clinical course on sick leave and disability pension. METHODS: Patients with relapsing-remitting MS (RRMS), secondary progressive MS (SPMS) and primary progressive MS (PPMS) were identified through the Swedish Multiple Sclerosis Registry. We calculated the mean annual prevalence and number of sick leave and disability pension days by clinical course, age and year pre- and post-diagnosis, and compared outcomes using Welch's t-tests and ANOVA models, mixed-effects regression and survival analysis. RESULTS: The sample included 5371 patients (4568 with RRMS, 390 with SPMS and 413 with PPMS). The mean annual number of days with sick leave and disability pension ranged from 101 at 1 year after diagnosis to 164 after 11 years for patients with RRMS. Corresponding estimates for PPMS were 188 and 311 days. Higher levels of absenteeism were observed in patients with PPMS versus RRMS 7 years before diagnosis for sick leave (P < 0.025) and 10 years before diagnosis for disability pension (P < 0.034). Differences between SPMS and PPMS were minor. CONCLUSIONS: Patients with RRMS had substantially lower levels of sick leave and disability pension over time compared with their counterparts with SPMS and PPMS, whereas labour-force absenteeism was similar for patients with SPMS and PPMS. These findings contribute to the understanding of the impact of MS on socioeconomic outcomes and help inform the discussion on the clinical classification of different courses of the disease.

Multiple sclerosis and risk of attempted and completed suicide - a cohort study.

BACKGROUND AND PURPOSE: Patients with multiple sclerosis (MS) are known to have an elevated suicide risk, but attempted suicide is incompletely investigated. The relation between education level and suicidality has not been investigated in MS patients. Our objective was to estimate attempted suicide and completed suicide risks amongst MS patients. METHODS: A total of 29 617 Swedish MS patients were identified through the Swedish Patient Register and matched with 296 164 people without MS from the general population. Cox regression analysis estimated hazard ratios (HRs) with 95% confidence intervals (CIs) for the association of MS with attempted and completed suicide, with adjustment for age, sex, education and calendar period. RESULTS: The adjusted HR for attempted suicide amongst MS patients is 2.18 (95% CI 1.97-2.43) compared with the general population cohort. For completed suicide the HR is 1.87 (95% CI 1.53-2.30). In both groups women are at higher risk of attempting suicide, whilst men are at higher risk of completing suicide. Education level is inversely associated with completed suicide amongst the non-MS cohort (0.68, 0.51-0.91), but not amongst MS patients (1.10, 0.60-2.04). CONCLUSION: Multiple sclerosis patients are at higher risk of both attempted and completed suicide. No evidence was found of an inverse association between educational level and risk of completed suicide amongst MS patients.

Genetic analysis of the isolated Faroe Islands reveals SORCS3 as a potential multiple sclerosis risk gene.

BACKGROUND: In search of the missing heritability in multiple sclerosis (MS), additional approaches adding to the genetic discoveries of large genome-wide association studies are warranted. OBJECTIVE: The objective of this research paper is to search for rare genetic MS risk variants in the genetically homogenous population of the isolated Faroe Islands. METHODS: Twenty-nine Faroese MS cases and 28 controls were genotyped with the HumanOmniExpressExome-chip. The individuals make up 1596 pair-combinations in which we searched for identical-by-descent shared segments using the PLINK-program. RESULTS: A segment spanning 63 SNPs with excess case-case-pair sharing was identified (0.00173 < p > 0.00212). A haplotype consisting of 42 of the 63 identified SNPs which spanned the entire the Sortilin-related vacuolar protein sorting 10 domain containing receptor 3 (SORCS3) gene had a carrier frequency of 0.34 in cases but was not present in any controls (p = 0.0008). CONCLUSION: This study revealed an oversharing in case-case-pairs of a segment spanning 63 SNPs and the entire SORCS3. While not previously associated with MS, SORCS3 appears to be important in neuronal plasticity through its binding of neurotrophin factors and involvement in glutamate homeostasis. Although additional work is needed to scrutinise the genetic effect of the SORCS3-covering haplotype, this study suggests that SORCS3 may also be important in MS pathogenesis.

Comparative analysis of first-year fingolimod and natalizumab drug discontinuation among Swedish patients with multiple sclerosis.

BACKGROUND: Natalizumab (NTZ) and fingolimod (FGL) are mainly used second line in relapsing-remitting multiple sclerosis (MS), although pivotal trials included mainly treatment-naïve patients. OBJECTIVE: This study aims to provide real-world data on safety and discontinuation rates. METHODS: Using IMSE, a drug monitoring registry for all newer MS drugs in Sweden, we analysed differences in baseline characteristics and 1-year drug survival for patients registered 2011-2013, initiating treatment with NTZ (n=640) or FGL (n=876). Among FGL initiators, n=383 (44%) had previously used NTZ (FGL(afterNTZ)). RESULTS: Compared with NTZ, the FGL cohort was older and more often male (36/38 years, 24%/33% males). Baseline Expanded Disability Status Scale was similar across groups, but MS Severity Score was higher in NTZ patients, and Symbol Digit Modalities Test and MS Impact Scale (MSIS-29) was higher in FGL(afterNTZ) versus FGL(NTZ-naïve) patients. Proportion on drug after 1 year was high, NTZ=87%, FGL(NTZ-naïve)=83% and FGL(afterNTZ)=76%. Adverse events was the most frequent reason for discontinuing FGL (FGL(NTZ-naïve)=9%, FGL(afterNTZ)=12%), and was significantly higher than on NTZ (3%). In contrast, the proportion of patients stopping treatment due to lack of effect was more similar: NTZ=4%, FGL(NTZ-naïve)=3%, FGL(afterNTZ)=8%. CONCLUSION: FGL and NTZ were both well tolerated, but FGL less so than NTZ, especially in patients switching to FGL from NTZ. Group differences were not explained by differences in recorded baseline characteristics.

The Swedish MS registry ­ clinical support tool and scientific resource.

The Swedish MS registry (SMSreg) is designed to assure quality health care for patients with multiple sclerosis (MS). It has been active since 2001 and web-based since 2004. It runs on government funding only and is used in all Swedish neurology departments. The SMSreg currently includes data on 14,500 of Sweden's estimated 17,500 prevalent patients with MS. One important function of SMSreg, to which participation is voluntary, is to serve as a tool for decision support and to provide an easy overview of the patient information needed at clinical visits. This is its core feature and explains why the majority of Swedish MS specialists contribute data. Another success factor for SMSreg is that entered data can be readily accessed, either through a query function into Excel format or through a set of predesigned tables and diagrams in which parameters can be selected. Recent development includes a portal allowing patients to view a summary of their registered data and to report a set of patient-reported outcomes. SMSreg data have been used in close to 100 published scientific reports. Current projects include an incidence cohort (EIMS), post-marketing cohorts of patients on novel disease-modifying drugs (IMSE), and a prevalence cohort (GEMS). As these studies combine physical sampling and questionnaire data with clinical documentation and possible linkage to other public registries, together they provide an excellent platform for integrated MS research.

All-cause mortality following a cancer diagnosis amongst multiple sclerosis patients: a Swedish population-based cohort study.

BACKGROUND AND PURPOSE: A reduced cancer risk amongst patients with multiple sclerosis (MS) has been reported. Theoretically, this could represent a genuine reduction in risk or, alternatively, 'diagnostic neglect', where cancer is undiagnosed when symptoms are misattributed to MS. OBJECTIVE: Assess all-cause mortality risk following a cancer diagnosis in patients with MS compared with a cohort without MS. PATIENTS: A cohort of MS patients (n = 19,364) and a cohort of the general population (n = 192,519) were extracted from national Swedish registers from 1969 to 2005. All-cause mortality after cancer in MS was compared with the general population. Poisson regression analysis was conducted in the MS and non-MS cohorts separately. The models were adjusted for follow-up duration, year at entry, sex, region and socioeconomic index. The two cohorts were combined and differences in mortality risk were assessed using interaction testing. RESULTS: The adjusted relative risk (and 95% confidence interval) for all-cause mortality following a cancer diagnosis in MS patients (compared with MS patients without cancer) is 3.06 (2.86-3.27; n = 1768) and amongst those without MS 5.73 (5.62-5.85; n = 24,965). This lower magnitude mortality risk in the MS patients was confirmed by multiplicative interaction testing (P < 0.001). CONCLUSIONS: A consistent pattern of lower magnitude of all-cause mortality risk following cancer in MS patients for a range of organ-specific cancer types was found. It suggests that cancer diagnoses tend not to be delayed in MS and diagnostic neglect is unlikely to account for the reduced cancer risk associated with MS. The lower magnitude cancer risk in MS may be due to disease-associated characteristics or exposures.

Obesity interacts with infectious mononucleosis in risk of multiple sclerosis.

BACKGROUND AND PURPOSE: The possible interaction between adolescent obesity and past infectious mononucleosis (IM) was investigated with regard to multiple sclerosis (MS) risk. METHODS: This report is based on two population-based case-control studies, one with incident cases (1780 cases, 3885 controls) and one with prevalent cases (4502 cases, 4039 controls). Subjects were categorized based on adolescent body mass index (BMI) and past IM and compared with regard to occurrence of MS by calculating odds ratios with 95% confidence intervals (CIs) employing logistic regression. A potential interaction between adolescent BMI and past IM was evaluated by calculating the attributable proportion due to interaction. RESULTS: Regardless of human leukocyte antigen (HLA) status, a substantial interaction was observed between adolescent obesity and past IM with regard to MS risk. The interaction was most evident when IM after the age of 10 was considered (attributable proportion due to interaction 0.8, 95% CI 0.6-1.0 in the incident study, and attributable proportion due to interaction 0.7, 95% CI 0.5-1.0 in the prevalent study). In the incident study, the odds ratio of MS was 14.7 (95% CI 5.9-36.6) amongst subjects with adolescent obesity and past IM after the age of 10, compared with subjects with none of these exposures. The corresponding odds ratio in the prevalent study was 13.2 (95% CI 5.2-33.6). CONCLUSIONS: An obese state both impacts the cellular immune response to infections and induces a state of chronic immune-mediated inflammation which may contribute to explain our finding of an interaction between adolescent BMI and past IM. Measures taken against adolescent obesity may thus be a preventive strategy against MS.

High inbreeding in the Faroe Islands does not appear to constitute a risk factor for multiple sclerosis.

BACKGROUND: Large population-based genome-wide association studies have identified several multiple sclerosis (MS) genetic risk variants, but the existing missing heritability warrants different strategies. Isolated populations offer an alternative way of searching for rare genetic variants and evaluating the possible role of consanguinity in the development of MS. Studies of consanguinity and MS risk have yielded conflicting results. OBJECTIVES: In this study we investigated the role of consanguinity on MS risk in the relatively isolated Faroe Islands, which have a presumed high level of inbreeding. METHODS: A total of 29 cases and 28 matched controls were genotyped and assessed for inbreeding coefficients, number of runs of homozygosity (ROH) at different lengths and observed number of homozygotes as measures of relatedness. Parametric and non-parametric statistical models were applied. RESULTS: Both cases and controls exhibited considerable relatedness demonstrated by very high inbreeding coefficients, large number of observed homozygotes and many long ROH. However, apart from the number of ROH ≥ 2.5 mega base pairs, no significant differences between the two groups were observed. CONCLUSIONS: Overall, no significant difference between cases and controls were found, indicating that consanguinity in itself does not appear to be an important risk factor for MS in the population of the Faroe Islands.

Multiple sclerosis clinical course and cardiovascular disease risk - Swedish cohort study.

BACKGROUND AND PURPOSE: Cardiovascular disease (CVD) risk amongst multiple sclerosis (MS) patients appears raised, but few studies have examined CVD risk amongst an unselected MS patient group. MS course may be relevant for CVD risk. Our aim was to assess CVD risk and variation by course in MS patients. METHODS: The Multiple Sclerosis Register identified 7667 patients who received an MS diagnosis between 1964 and 2005. They were matched by age, period, region and sex with 76 045 members of the general population without MS using Swedish registers. Poisson regression compared the two cohorts to estimate the relative risk for CVD, overall, as well as grouped and individual CVD diagnoses. RESULTS: MS patients had an increased adjusted relative risk (with 95% confidence intervals; number of MS cohort events) for CVD of 1.31 (1.22-1.41; n = 847), with some variation by course: relapsing-remitting 1.38 (1.17-1.62; n = 168); secondary progressive 1.30 (1.18-1.53; n = 405) and primary progressive 1.15 (0.93-1.41; n = 108). The association for the relapsing-remitting course was not significant after excluding the first year of follow-up. Overall incidence rates per 1000 person-years for CVD are 11.8 (11.06-12.66) for the MS cohort and 8.8 (8.60-9.05) for the non-MS cohort. The most pronounced association was for deep vein thrombosis: relapsing-remitting 2.16 (1.21-3.87; n = 14), secondary progressive 3.41 (2.45-4.75; n = 52) and primary progressive 3.57 (1.95-6.56; n = 15). MS was associated with ischaemic stroke but largely during the first year of follow-up. MS was associated with a decreased relative risk for angina pectoris and atrial fibrillation. CONCLUSIONS: There is a significantly increased relative risk for CVD in MS, particularly for venous thromboembolic disorders in progressive MS, suggesting immobility as a possible factor. An increased frequency of ischaemic stroke in MS is most probably due to surveillance bias resulting from diagnostic investigations for MS. There is no increased relative risk for ischaemic heart disease in MS and atrial fibrillation appears to be less common than amongst the general population.

Variability in the CIITA gene interacts with HLA in multiple sclerosis.

The human leukocyte antigen (HLA) is the main genetic determinant of multiple sclerosis (MS) risk. Within the HLA, the class II HLA-DRB1*15:01 allele exerts a disease-promoting effect, whereas the class I HLA-A*02 allele is protective. The CIITA gene is crucial for expression of class II HLA molecules and has previously been found to associate with several autoimmune diseases, including MS and type 1 diabetes. We here performed association analyses with CIITA in 2000 MS cases and up to 6900 controls as well as interaction analysis with HLA. We find that the previously investigated single-nucleotide polymorphism rs4774 is associated with MS risk in cases carrying the HLA-DRB1*15 allele (P=0.01, odds ratio (OR): 1.21, 95% confidence interval (CI): 1.04-1.40) or the HLA-A*02 allele (P=0.01, OR: 1.33, 95% CI: 1.07-1.64) and that these associations are independent of the adjacent confirmed MS susceptibility gene CLEC16A. We also confirm interaction between rs4774 and HLA-DRB1*15:01 such that individuals carrying the risk allele for rs4774 and HLA-DRB1*15:01 have a higher than expected risk for MS. In conclusion, our findings support previous data that variability in the CIITA gene affects MS risk, but also that the effect is modulated by MS-associated HLA haplotypes. These findings further underscore the biological importance of HLA for MS risk.

Reverse causality behind the association between reproductive history and MS.

BACKGROUND: Possible associations between childbearing patterns and multiple sclerosis (MS) risk have been studied for a long time, with conflicting results. We aimed to investigate the influence of reproductive history on MS risk. METHODS: Using a Swedish population-based case-control study involving incident cases of MS (1798 cases, 3907 controls), we calculated odds ratios (OR) for MS comparing parents with childless subjects together with 95% confidence intervals (CI) employing logistic regression. RESULTS: Overall, there was an association between having children and reduced MS risk among both sexes. Subjects who had become parents within five years prior to the index year had a substantially reduced risk of developing MS (OR 0.6, 95% CI 0.5-0.8 for women, and OR 0.4, 95% CI 0.3-0.6 for men). No association between having children and MS risk was observed when more than 10 years had passed since the birth of the last child. We found no association between increasing offspring number and MS risk. CONCLUSIONS: The observed association between reproductive history and MS risk is restricted to a limited time period preceding the index year, with similar findings in both sexes, which contradicts biologic impact of pregnancy on MS risk and argues in favor of reverse causality, i.e. that fecundity is affected by yet-undiagnosed MS.

Cytomegalovirus seropositivity is negatively associated with multiple sclerosis.

BACKGROUND: Epidemiological data suggest a role for common viruses in the pathogenesis of multiple sclerosis (MS), and recent data showed a negative association of past cytomegalovirus (CMV) infection on pediatric MS risk. OBJECTIVE: Our aim was to analyze the association of CMV infection with MS risk in an adult case-control material. A meta-analysis was performed to validate our findings. METHODS: Epidemiological Investigation in MS (EIMS) is a case-control study with incident cases and population-based controls. Anti-CMV antibody titers were measured with ELISA, and HLA-A and DRB1 genotyping was performed with SSP-PCR, in 658 MS cases, who all fulfilled the McDonald criteria for MS, and 786 controls. RESULTS: CMV seropositivity was associated with a decreased MS risk, OR = 0.73 (0.58-0.92 95% CI), p = 0.005, adjusted for index age, gender, smoking, sun exposure, EBNA1 IgG titer and HLA-A*02 and DRB1*15. When we removed all cases and controls younger than 18 years at index, the protective effect was still apparent. CONCLUSIONS: CMV is negatively associated with adult-onset MS pathology, consistent with results from a study on pediatric MS cases. It remains to be shown whether this negative association is due to a true protective effect of CMV infection on MS risk.

Hospital admission due to infections in multiple sclerosis patients.

BACKGROUND AND PURPOSE: Multiple sclerosis (MS) patients are at increased infection risk. Here the influences of susceptibility, severity and surveillance bias on infection-related hospital admission are assessed. METHODS: Swedish registers identified 20,276 patients with MS, matched with 203,951 people from the general population without MS. Risk of first hospital admission for infection and mortality over 36 years was estimated by Poisson regression. RESULTS: Multiple sclerosis was associated with an increased hospital admission risk for all infections, with an adjusted relative risk (and 95% confidence interval) of 4.26 (4.13-4.40). A proportion of this raised risk was probably due to surveillance and referral bias, although a raised risk remained when MS was compared with other immune-mediated diseases. The 1-month mortality rate following hospital admission for infection was higher in MS patients than in the comparison cohort, with a relative risk of 4.69 (4.21-5.22). There was no clear temporal trend in the results, and risks were higher in males and varied by MS phenotype. CONCLUSIONS: Higher hospital admission rates among MS patients for infection are likely to be due to a combination of surveillance bias, cautious medical management and greater susceptibility to severe infections. MS-related functional limitations may increase infection risk and this should be considered in MS management.

Exposure to anaesthetic agents does not affect multiple sclerosis risk.

BACKGROUND AND PURPOSE: It has been hypothesized that exposure to anaesthetic agents, some of which are chemically related to organic solvents, may affect the risk of developing multiple sclerosis (MS). The aim of this study was to estimate the influence of occupational exposure to anaesthetic agents on the risk for MS. We further aimed to investigate the impact of general anaesthesia and usage of nitrous oxide. METHODS: This report is based on two population-based, case-control studies, one with incident cases (1798 cases, 3907 controls) and one with prevalent cases (5216 cases, 4701 controls). Using logistic regression, the occurrence of MS among subjects who have been exposed to anaesthetic agents was compared with that of those who have never been exposed by calculating the odds ratio with a 95% confidence interval. RESULTS: No association was found between occupational exposure to anaesthetic agents and risk of developing MS, also general anaesthesia or usage of nitrous oxide had no impact on MS risk. CONCLUSIONS: Neither occupational exposure to anaesthetic agents, nor general anaesthesia or usage of nitrous oxide has any impact on MS risk and is safe also for people with a genetic susceptibility to the disease. However, further studies would be valuable in order to clarify whether other forms of organic solvents contribute to the triggering of MS.

Nicotine might have a protective effect in the etiology of multiple sclerosis.

OBJECTIVE: The use of moist snuff is common in Sweden and leads to exposure to high doses of nicotine. Recent studies indicate that exposure to nicotine could modulate immune responses. The aim of this study was to investigate the influence of snuff use on the risk of developing multiple sclerosis (MS), taking smoking habits into consideration. METHODS: In two Swedish population-based, case-control studies (7883 cases, 9437 controls), subjects with different snuff use habits were compared regarding MS risk, by calculating odds ratios (ORs) with 95% confidence intervals (CIs). RESULTS: Snuff-takers have a decreased risk of developing MS compared with those who have never used moist snuff (OR 0.83, 95% CI 0.75-0.92), and we found clear evidence of an inverse dose-response correlation between cumulative dose of snuff use and the risk of developing the disease. We further observed that subjects who combined smoking and snuff use had a significantly lower risk for MS than smokers who had never used moist snuff, also after adjustment for amount of smoking. CONCLUSIONS: Our results add evidence to the hypothesis that nicotine exerts anti-inflammatory and immune-modulating effects in a way that might decrease the risk of developing MS.

Characterization of anti-natalizumab antibodies in multiple sclerosis patients.

BACKGROUND: A small proportion of multiple sclerosis (MS) patients treated with natalizumab develop anti-drug antibodies. OBJECTIVE: The objective of this paper is to characterize the anti-natalizumab antibody response and to investigate differences between persistently and transiently antibody-positive patients. METHODS: Screening for anti-natalizumab antibodies was performed using a standardized bridging ELISA. Antibody-positive samples were further analyzed for IgM and IgG1-4 antibodies using ELISA and ImmunoCAP®. RESULTS: Anti-natalizumab antibodies developed in 57 of 1379 (4.1%) treated patients after a median treatment duration of three months. Of the positive patients, 20 (35%) patients reverted to negative, 19 (33%) patients were confirmed persistently positive and 18 (32%) patients were unconfirmed positive. Significantly higher anti-natalizumab antibody levels were detected in persistently compared to transiently positive patients. A cutoff value predicting persistence of antibodies could be determined with a sensitivity of 0.84 and a specificity of 0.80. IgM and IgG4 antibody levels were significantly higher in persistently compared to transiently positive patients, and IgG1, IgG2 and IgG4 increased significantly over time. CONCLUSIONS: The level of total anti-natalizumab antibodies in a first positive sample can be used to predict patients at risk for persisting antibody positivity. However, neither IgM nor IgG1-4 antibodies could be used to discriminate between transiently and persistently positive patients.