A nationwide survey of the prevalence of multiple sclerosis in immigrant populations of Sweden

Multiple sclerosis in Somali Americans: Nature or nurture?

BACKGROUND

Differences in the MS course between White and Black populations is well accepted. The existence of a large Somali immigrant population in Minnesota facilitates a study of MS characteristics in this immigrant native African population. The objective of this study was to compare Somali American (SA), African American (AA), and White American (WA) persons with MS (pwMS) regarding clinical features and disease modifying therapy (DMT) use.

METHODS

This single center (Mayo Clinic) geographically-restricted retrospective cohort study (residing within 250 miles of Rochester, MN, USA) included participants seen before May 2023. Age at immigration to the USA; age at MS onset; DMT use/type; MS phase/phenotype; age at progressive MS (PMS) onset; and proportion with severe MS (expanded disability status scale-EDSS ≥6) were examined.

RESULTS

18 SApwMS, 92 AApwMS, and 94 WApwMS were included. Of the 15 SApwMS not born in USA, 3/15 immigrated pre-puberty, 3/15 peri‑puberty, 8/15 post-puberty, and 1/15 at an unknown date. SApwMS were younger at MS onset (median years, interquartile range (IQR)=25, 22-33 vs. AApwMS: 31, 25-38; p = 0.049 vs. WApwMS: 35, 27-41; p = 0.022). DMT use frequencies were 13/19 SApwMS, 69/92 AApwMS, 80/94 WApwMS (p > 0.05). SApwMS were treated with DMT earlier than AApwMS (HR 2.16, p = 0.012) and WApwMS (HR 1.86, p = 0.041). SApwMS were less commonly treated with natalizumab (SApwMS 0 %, AApwMS 13 %, WApwMS 25 %; p = 0.035) and anti-CD20 therapies (SApwMS 23 %, AApwMS 23 %, WApwMS 48 %; p = 0.005). PMS occurred in 3/19 SApwMS, 28/92 AApwMS and 29/94 WApwMS (p > 0.05). Age of PMS onset in SApwMS (47 years, 34-57) was similar to WApwMS (47 years, 31-71; p > 0.05) but older than AApwMS (41 years, 18-7; p = 0.008).

CONCLUSIONS

SApwMS that recently immigrated to the USA have similar disease course to WApwMS, and better than AApwMS from the same geographical region.

Prevalence and disease disability in immigrants with multiple sclerosis in Malmö, southern Sweden

BACKGROUND

Multiple sclerosis (MS) is the most common chronic demyelinating disease of the central nervous system and the major non-traumatic cause of permanent disability in young adults. Several migration studies have been performed over the years suggesting a pattern of higher disease disability in certain ethnic groups. To our knowledge, differences in disease progression in immigrants have not been studied in Sweden before. Thus, the aims of our study were to estimate the prevalence of multiple sclerosis among first-generation immigrants in the City of Malmö and to compare differences in disease severity with the native population.

METHODS

All persons with multiple sclerosis living in Malmö on prevalence day 31 Dec 2010 were included. Cases were classified according to the country of birth into Scandinavians, Western and non-Western.

RESULTS

The crude prevalence was 100/100,000 (95% CI, 80-124) among first-generation immigrants, 154/100,000 (95% CI, 137-173) among individuals with Scandinavian background, 123/100,000 (95% CI, 94-162) in the Western group and 76/100,000 (95% CI, 53-108) in the non-Western group. The mean Multiple Sclerosis Severity Score (MSSS) value among Scandinavians was 4.2 (SD 3.5), whereas the figures in the immigrant group were 4.6 (SD 3.3) and 5.2 (SD 3.7) among Westerns respectively non-Westerns, which differences were not statistically significant. When adjusting for gender, age at onset and initial disease course, the mean MSSS difference between the non-Western and the Scandinavian individuals was 1.7 (95% CI 0.18-3.3, p = 0.030). There were no differences on time to diagnosis or the time from diagnosis to treatment initiation between the three groups.

CONCLUSIONS

We found a lower prevalence among Western and non-Western first-generation immigrants compared to the Scandinavian population and a more severe disease in non-Western immigrants than in Scandinavians.

The role of ethnicity and native-country income in multiple sclerosis: the Italian multicentre study (MS-MigIT)

OBJECTIVE

Multiple sclerosis (MS) is a complex disorder in which environmental and genetic factors interact modifying disease risk and course. This multicentre, case-control study involving 18 Italian MS Centres investigated MS course by ethnicity and native-country economic status in foreign-born patients living in Italy.

METHODS

We identified 457 MS patients who migrated to Italy and 893 age- and sex-matched native-born Italian patients. In our population, 1225 (93.2%) subjects were White Europeans and White Northern Americans (WENA) and 89 (6.8%) patients were from other ethnical groups (OEG); 1109 (82.1%) patients were born in a high-income (HI) Country and 241 (17.9%) in a low-middle-income (LMI) Country. Medical records and patients interviews were used to collect demographic and disease data.

RESULTS

We included 1350 individuals (973 women and 377 men); mean (SD) age was 45.0 (11.7) years. At onset, 25.45% OEG patients vs 12.47% WENA (p = 0.039) had > 3 STIR spine lesions. At recruitment, the same group featured mean (SD) EDSS score of 2.85 (2.23) vs 2.64 (2.28) (p = 0.044) reached in 8.9 (9.0) vs 12.0 (9.0) years (p = 0.018) and underwent 1.10 (4.44) vs. 0.99 (0.40) annual MRI examinations (p = 0.035). At disease onset, patients from LMI countries had higher EDSS score than HI patients (2.40 (1.43) vs 1.99 (1.17); p = 0.032).

DISCUSSION

Our results suggested that both ethnicity and socio-economic status of native country shape MS presentation and course and should be considered for an appropriate management of patients. To the best of our knowledge, this is the first study reporting on the impact of ethnicity in MS at an individual level and beyond an ecological population-perspective.

Towards a global view of multiple sclerosis genetics

Multiple sclerosis (MS) is a neuroimmunological disorder of the CNS with a strong heritable component. The genetic architecture of MS susceptibility is well understood in populations of European ancestry. However, the extent to which this architecture explains MS susceptibility in populations of non-European ancestry remains unclear. In this Perspective article, we outline the scientific arguments for studying MS genetics in ancestrally diverse populations. We argue that this approach is likely to yield insights that could benefit individuals with MS from all ancestral groups. We explore the logistical and theoretical challenges that have held back this field to date and conclude that, despite these challenges, inclusion of participants of non-European ancestry in MS genetics studies will ultimately be of value to all patients with MS worldwide.

High-resolution HLA class II sequencing of Swedish multiple sclerosis patients

Multiple sclerosis (MS) is a chronic neurological disease believed to be caused by autoimmune pathogenesis. The aetiology is likely explained by a complex interplay between inherited and environmental factors. Genetic investigations into MS have been conducted for over 50 years, yielding >100 associations to date. Globally, the strongest linkage is with the human leukocyte antigen (HLA) HLA-DRB5*01:01:01-DRB1*15:01:01-DQA1*01:02:01-DQB1*06:02:01 haplotype. Here, high-resolution sequencing of HLA was used to determine the alleles of DRB3, DRB4, DRB5, DRB1, DQA1, DQB1, DPA1 and DPB1 as well as their extended haplotypes and genotypes in 100 Swedish MS patients. Results were compared to 636 population controls. The heterogeneity in HLA associations with MS was demonstrated; among 100 patients, 69 extended HLA-DR-DQ genotypes were found. Three extended HLA-DR-DQ genotypes were found to be correlated to MS; HLA-DRB5*01:01:01-DRB1*15:01:01-DQA1*01:02:01-DQB1*06:02:01 haplotype together with (A) HLA-DRB4*01:01:01//DRB4*01:01:01:01-DRB1*07:01:01-DQA1*02:01//02:01:01-DQB1*02:02:01, (B) HLA-DRBX*null-DRB1*08:01:01-DQA1*04:01:01-DQB1*04:02:01, and (C) HLA-DRB3*01:01:02-DRB1*03:01:01-DQA1*05:01:01-DQB1*02:01:01. At the allelic level, HLA-DRB3*01:01:02 was considered protective against MS. However, when combined with HLA-DRB3*01:01:02-DRB1*03:01:01-DQA1*05:01:01-DQB1*02:01:01, this extended haplotype was considered a predisposing risk factor. This highlights the limitations as included with investigations of single alleles relative to those of extended haplotypes/genotypes. In conclusion, with 69 genotypes presented among 100 patients, high-resolution sequencing was conducted to underscore the wide polymorphisms present among MS patients. Additional studies in larger cohorts will be of importance to define MS among the patient group not associated with HLA-DRB5*01:01:01-DRB1*15:01:01-DQA1*01:02:01-DQB1*06:02:01.

Age-dependent VDR peak DNA methylation as a mechanism for latitude-dependent multiple sclerosis risk

BACKGROUND

The mechanisms linking UV radiation and vitamin D exposure to the risk of acquiring the latitude and critical period-dependent autoimmune disease, multiple sclerosis, is unclear. We examined the effect of vitamin D on DNA methylation and DNA methylation at vitamin D receptor binding sites in adult and paediatric myeloid cells. This was accomplished through differentiating CD34+ haematopoietic progenitors into CD14+ mononuclear phagocytes, in the presence and absence of calcitriol.

RESULTS

Few DNA methylation changes occurred in cells treated with calcitriol. However, several VDR-binding sites demonstrated increased DNA methylation in cells of adult origin when compared to cells of paediatric origin. This phenomenon was not observed at other transcription factor binding sites. Genes associated with these sites were enriched for intracellular signalling and cell activation pathways involved in myeloid cell differentiation and adaptive immune system regulation.

CONCLUSION

These results suggest vitamin D exposure at critical periods during development may contribute to latitude-related differences in autoimmune disease incidence.

Nature Exposure and Its Effects on Immune System Functioning: A Systematic Review

Given the drastic changes in our lifestyles and ecosystems worldwide, the potential health effects of natural environments have grown into a highly pervasive topic. Recent scientific findings suggest beneficial effects from nature exposure on human immune responses. This review aims at providing a comprehensive overview of literature published on immunomodulatory effects of nature exposure by inhalation of natural substances. A systematic database search was performed in SCOPUS and PubMed. The quality and potential bias of included studies (n = 33) were assessed by applying the EPHPP (Effective Public Health Practice Project) tool for human studies and the ARRIVE (Animal Research: Reporting of In Vivo Experiments) and SYRCLE (Systematic Review Centre for Laboratory Animal Experimentation) tools for animal studies. The synthesis of reviewed studies points to positive effects of nature exposure on immunological health parameters; such as anti-inflammatory, anti-allergic, anti-asthmatic effects or increased NK (natural killer) cell activity. Decreased expression of pro-inflammatory molecules, infiltration of leukocytes and release of cytotoxic mediators are outcomes that may serve as a baseline for further studies. However, partially weak study designs evoked uncertainties about outcome reproducibility and key questions remain open concerning effect sizes, duration of exposure and contributions of specific vegetation or ecosystem types.

Vitamin D and its Effects on DNA Methylation in Development, Aging, and Disease

DNA methylation is increasingly being recognized as a mechanism through which environmental exposures confer disease risk. Several studies have examined the association between vitamin D and changes in DNA methylation in areas as diverse as human and animal development, genomic stability, chronic disease risk, and malignancy. In many cases, they have demonstrated clear associations between vitamin D and DNA methylation in candidate disease pathways. Despite this, a clear understanding of the mechanisms by which these factors interact is unclear. This paper reviews the current understanding of the effects of vitamin D on DNA methylation. In light of current knowledge in the field, the potential mechanisms mediating vitamin D effects on DNA methylation are discussed, as are the limiting factors and future avenues for research into this exciting area.

Multiple sclerosis among first- and second-generation immigrant groups in Sweden

OBJECTIVES

Risk of multiple sclerosis (MS) is low among first-generation immigrants in Sweden. We aimed to study incident MS in first- and second-generation immigrant groups.

MATERIALS & METHODS

We included adults aged 18 years and older in Sweden in first-generation (n = 6 042 891) and second-generation (n = 4 860 469) sub-studies. MS was defined via two diagnoses in the Swedish National Patient Register. MS risk was estimated by Cox regression, with hazard ratios (HRs) and 95% confidence intervals (CI), in different immigrant groups, using Swedish-born as referents in first-generation sub-study, and individuals with Swedish-born parents in the second-generation. Full models were adjusted for age, geographic residence in Sweden, educational level, marital status, neighborhood socioeconomic status, and co-morbidity.

RESULTS

MS was diagnosed among 10 746 individuals in the first-generation sub-study, (men 3055 and women 7691), and 11 737 in the second-generation sub-study (men 3549 and women 8188) in the period 1998-2015. The annual incidence rate was higher in Swedish-born compared to foreign-born, 11.5 vs 6.3 per 100 000 person-years (age-standardized to the European standard population). Fully adjusted HRs were lower in first-generation immigrant men (HR 0.72, 0.64-0.82) and women (HR 0.67, 0.62-0.73), and in second-generation immigrant men (HR 0.88, 0.79-0.97) and women (HR 0.79; 0.73-0.84). Among first-generation immigrants, lower HRs were found in most groups.

SIGNIFICANCE

The MS risk was lower in first- and second-generation immigrants compared to Swedish-born or individuals with Swedish-born parents.

Changes in multiple sclerosis epidemiology in Finland over five decades

Finland is a high-risk region for multiple sclerosis (MS) with several epidemiological studies on the subject published since 1964, but these have not been comprehensively scrutinized. The objective of this study was to review previous studies of Finnish MS epidemiology, introduce new data on MS prevalence in western parts of Finland and do further analyses on data from previous studies. We performed a systematic search on articles regarding MS epidemiology in Finland in PubMed database, and all relevant articles were included in this review. MS prevalences in the western hospital districts of Vaasa, South Ostrobothnia and Pirkanmaa were calculated in 1980-2007 by using previously unpublished data obtained from a retrospective search from hospital administrative registries. To enhance comparability of the epidemiological figures, we calculated age-standardized prevalence of MS from the new data from western hospital districts and previous data from North Ostrobothnia, Southwest Finland and North Karelia. Marked regional differences in MS epidemiology were confirmed with concentration of the disease in the western and south-western parts of the country. The highest regional age-standardized MS prevalence of 288/100 000 was reported in South Ostrobothnia in 2007. A clear and stable increase in MS prevalence was observed through the decades, but the only marked increase in incidence happened in 1990s. Methodological differences hampered direct comparisons of different studies, highlighting the importance of common principles of reporting and standardizing the epidemiological figures. More comprehensive studies on MS epidemiology are still warranted to yield important information concerning the aetiology of the disease.

Multiple sclerosis among first- and second-generation immigrants in Denmark: a population-based cohort study

Multiple sclerosis is a disease with a highly variable incidence worldwide. While knowledge about multiple sclerosis risk factors has grown over the years, the aetiology of multiple sclerosis has still not been fully established. We examined multiple sclerosis incidence rates among first-generation immigrants in Denmark, a high-incidence country, and their Danish-born children (second-generation immigrants), to evaluate the importance and timing of exposure to environmental factors in the aetiology of multiple sclerosis. By means of the Danish Civil Registration System we identified 9 121 187 individuals living in Denmark between 1968 and 2015, including 1 176 419 first-generation and 184 282 second-generation immigrants. Study participants were followed for multiple sclerosis in the Danish Multiple Sclerosis Registry from 1968 to 2015. The relative risk (RR) of multiple sclerosis according to immigration status was estimated by means of multiple sclerosis incidence rate ratios obtained in log-linear Poisson regression analysis. Altogether, 16 905 cases of multiple sclerosis were identified in the study cohort, 578 among first-generation and 106 among second-generation immigrants. Multiple sclerosis risk among first-generation immigrants whose parents were born in low, intermediate and high multiple sclerosis risk areas were 21% (RR = 0.21; 95% CI: 0.16-0.28), 43% (RR = 0.43; 95% CI: 0.36-0.50) and 75% (RR = 0.75; 95% CI: 0.67-0.83), respectively, of that among ethnic Danes (test for trend P < 0.0001). First-generation immigrants arriving in Denmark before age 15 years had a multiple sclerosis risk higher than that in their country of birth but lower than that in Denmark, reaching on average 69% of the multiple sclerosis risk among ethnic Danes (RR = 0.69; 95% CI: 0.55-0.87). Multiple sclerosis risk among individuals who came to Denmark at a later age remained closer to that of their country of birth, corresponding to 45% of the multiple sclerosis risk among ethnic Danes (RR = 0.45; 95% CI: 0.41-0.49). Our study supports the idea that environmental factors exerting their role in childhood or adolescence may be of aetiological relevance in multiple sclerosis.

MS risk in immigrants in the McDonald era: A population-based study in Ontario, Canada

OBJECTIVE

To determine risk factors for multiple sclerosis (MS) in immigrants and to compare MS risk in immigrants and long-term residents in Ontario, Canada.

METHODS

We applied a validated algorithm to linked, population-based immigration and health claims data to identify incident cases of MS in immigrants and long-term residents between 1994 and 2016. We conducted 2 multivariable Cox proportional hazards regression analyses: 1 analysis limited to the immigrant cohort assessing potential risk factors for developing MS, and 1 analysis comparing MS risk between immigrants and matched long-term residents (1:3 match).

RESULTS

We identified 2,304,302 immigrants for the immigrant-only analysis, of whom 1,526 (0.066%) developed MS. Risk was greatest in those <15 years old at landing (referent <15 years; 16-30 years: hazard ratio [HR] 0.73, 95% confidence interval [CI] 0.63-0.85; 31-45 years: HR 0.55, 95% CI 0.47-0.64). Immigrants from the Middle East (HR 1.22, 95% CI 1.06-1.40) were at greater MS risk than immigrants from Western nations; all other regions had lower risk (p < 0.0001). The matched analysis included 2,207,751 immigrants and 6,362,169 long-term residents. Immigrants were less likely to develop MS than long-term residents (p < 0.0001), although this lower risk was attenuated with longer residence in Canada.

CONCLUSIONS

MS incidence in immigrants to Ontario, Canada, varied widely by region of origin, with greatest risk seen in those from the Middle East. Longer residence in Canada was associated with increased risk, even with migration in adulthood, suggesting that environmental exposures into adulthood contribute to MS risk.

Changing patterns of multiple sclerosis in Korea: Toward a more baseline MRI lesions and intrathecal humoral immune responses

BACKGROUND

The environmental risks of multiple sclerosis (MS), including adolescent obesity and vitamin D deficiency, are increasing in Korea. We aimed to determine whether the patterns and/or severity of MS in Korea can change according to the year of birth or disease onset.

METHODS

Two hundred and sixty-six patients with adult-onset MS, including 164 with an available baseline magnetic resonance imaging (MRI), were retrospectively included from 17 nationwide referral hospitals in Korea. The demographics, MRI T2 lesion burden at disease onset, cerebrospinal fluid markers, and prognosis were assessed.

RESULTS

The birth year, time from disease onset to first MRI, and female sex were associated with a higher number of baseline MRI T2 lesions. The birth year was also associated with the presence of oligoclonal band in the cerebrospinal fluid and high immunoglobin G index. An increased female/male ratio was observed among those with a more recent year of birth and/or disease onset.

CONCLUSIONS

In Korea, the disease pattern of adult-onset MS may be changing toward a more baseline T2 MRI lesions, intrathecal humoral immune responses, and also higher female ratio.

Changing epidemiology of immune-mediated inflammatory diseases in immigrants: A systematic review of population-based studies

BACKGROUND

Immune-mediated inflammatory diseases (IMIDs) are systemic diseases of multifactorial etiology that share aberrant immune responses as the common final pathway. With rising globalization, their incidence is increasing in developing countries and among immigrants. Our primary objective was to systematically review the epidemiology of IMIDs in immigrants and conduct a meta-analysis to estimate the risk of IMIDs in immigrant populations according to their origin and destination countries.

METHODS

We systematically searched five biomedical databases and reviewed population-based studies, from inception through August 2018, that reported incidence or prevalence data of inflammatory bowel disease (IBD), multiple sclerosis (MS), type 1 diabetes (T1D), systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), ankylosing spondylitis (AS) or psoriasis and psoriatic arthritis (PPA) among immigrants and the host population.

RESULTS

The incidence and prevalence of IMIDs among immigrants differ from host populations, and evolve over subsequent generations. The risk of IBD among immigrants approximates that in hosts, especially among South Asians, with ulcerative colitis incidence changing prior to Crohn's disease incidence. MS risk is highest in Iranian immigrants, T1D in African immigrants and SLE in African and Iraqi immigrants. Data on other IMIDs are sparse. Significant heterogeneity between the studies precluded meta-analysis.

CONCLUSION

Based on our systematic review, the epidemiology of IMIDs among immigrants varies according to native and host countries, immigrant generation, and IMID type. The rapid evolution suggests a role for non-genetic factors and gene-environment interactions. Future studies should focus on these pattern shifts, given implications of rising global burden of IMIDs and immigration.

Lifestyle and Environmental Factors in Multiple Sclerosis

Lifestyle and environmental factors potently influence the risk of multiple sclerosis (MS), because genetic predisposition only explains a fraction of the risk increase. There is strong evidence for associations of Epstein-Barr virus (EBV) infection, smoking, sun exposure/vitamin D, and adolescent obesity to risk of MS. There is also circumstantial evidence on organic solvents and shift work, all associate with greater risk, although certain factors like nicotine, alcohol, and a high coffee consumption associate with a reduced risk. Certain factors, smoking, EBV infection, and obesity interact with human leukocyte antigen (HLA) risk genes, arguing for a pathogenic pathway involving adaptive immunity. There is a potential for prevention, in particular for people at greater risk such as relatives of individuals with MS. All of the described factors for MS may influence adaptive and/or innate immunity, as has been argued for MS risk gene variants.

Cross-Domain and Viral Interactions in the Microbiome

The importance of the microbiome to human health is increasingly recognized and has become a major focus of recent research. However, much of the work has focused on a few aspects, particularly the bacterial component of the microbiome, most frequently in the gastrointestinal tract. Yet humans and other animals can be colonized by a wide array of organisms spanning all domains of life, including bacteria and archaea, unicellular eukaryotes such as fungi, multicellular eukaryotes such as helminths, and viruses. As they share the same host niches, they can compete with, synergize with, and antagonize each other, with potential impacts on their host. Here, we discuss these major groups making up the human microbiome, with a focus on how they interact with each other and their multicellular host.

Signaling pathways and therapeutic perspectives related to environmental factors associated with multiple sclerosis

Multiple sclerosis (MS) is an immune-mediated demyelinating disorder of unknown etiology. Both genetic-susceptibility and environment exposures, including vitamin D deficiency, Epstein-Barr viral and Herpesvirus (HHV-6) infections are strongly implicated in the activation of T cells and MS-pathogenesis. Despite precise knowledge of how these factors could be operating alone or in combination to facilitate and aggravate the disease progression, it is clear that prolonged induction of inflammatory molecules and recruitment of other immune cells by the activated T cells results in demyelination and axonal damage. It is imperative to understand the risk factors associated with MS progression and how these factors contribute to disease pathology. Understanding of the underlying mechanisms of what factors triggers activation of T cells to attack myelin antigen are important to strategize therapeutics and therapies against MS. Current review provides a detailed literature to understand the role of both pathogenic and non-pathogenic factors on the impact of MS.

Environmental factors and their interactions with risk genotypes in MS susceptibility

PURPOSE OF REVIEW

The area of multiple sclerosis (MS) epidemiology has expanded during the last few years. Established lifestyle and environmental factors influencing MS risk are Epstein-Barr virus infection, sun exposure/vitamin D, and smoking. We review these factors and a series of other potential candidates implicated in the pathogenesis of MS and how environmental factors interact with genetic susceptibility with regard to disease risk.

RECENT FINDINGS

On top of established MS-associated factors, there is now strong evidence for influence of adolescent obesity, exposure to organic solvents and shift work, all demonstrating increased risk of disease. Other factors, such as nicotine, alcohol, and high coffee consumption are associated with decreased MS risk. A number of lifestyle/environmental factors, including smoking and obesity, seem to interact with MS risk human leukocyte antigen genes, conferring much stronger effects on disease risk among those exposed to both factors. Furthermore, an interaction between two environmental factors, obesity and infectious mononucleosis, with regard to MS risk, has been demonstrated in two independent studies.

SUMMARY

MS is a complex disease for which both genetic susceptibility and lifestyle/environmental factors are important, and where the latter may be of great importance. Lifestyle and environmental factors can often be modified and may denote pathogenic pathways.

Prevalence and clinical aspects of immigrants with myasthenia gravis in northern Europe

INTRODUCTION

Multiethnic studies can provide etiological clues toward the genetic and environmental influence of a disease. The aim of this study was to determine prevalence and clinical features of myasthenia gravis (MG) in immigrants compared with native patients in 2 population-based cohorts.

METHODS

This cross-sectional study included 843 MG patients (375 from Norway and 468 from the Netherlands). Ethnic background was defined by questionnaires.

RESULTS

Among the participating MG patients, 163 of 843 (19.3%) were first or second generation immigrants, mainly from Europe, Asia, and South America. No marked prevalence differences were found between immigrants and native ethnic groups. MG with muscle specific kinase antibodies and MG with thymoma were more frequent in Asian MG immigrants compared with other ethnic groups (8% vs. 0-4%; P < 0.001 and 21% vs. 6-10%; P < 0.001), respectively.

CONCLUSIONS

Our findings indicate that Asian immigrant MG patients carry genetic factors or environmental/lifestyle factors which contribute to their specific phenotype, even after migration. Muscle Nerve 55: 819-827, 2017.

Multiple Sclerosis Epidemiology in Europe

Multiple sclerosis is characterized by a non-homogeneous distribution around the world. Some authors in past described a latitude gradient, with increasing risk from the equator to North and South Poles, but this theory is still controversial. Regarding Europe, there are many articles in the literature concerning the epidemiology of this disease but, unfortunately, they are not always comparable due to different methodologies, they do not cover all countries in the continent, and most of them reported data of small areas and rarely at a national level. In 2012 there were 20 national registries that could help to describe the epidemiology of the disease and, in addition, there is an European Register for Multiple Sclerosis that collect data from already existing national or regional MS registries and databases. Another valid alternative to obtain epidemiological data, also at national level, in a routinely and cost-saving way is through administrative data that are of increasing interest in the last years.

Interactions between genetic, lifestyle and environmental risk factors for multiple sclerosis

Genetic predisposition to multiple sclerosis (MS) only explains a fraction of the disease risk; lifestyle and environmental factors are key contributors to the risk of MS. Importantly, these nongenetic factors can influence pathogenetic pathways, and some of them can be modified. Besides established MS-associated risk factors - high latitude, female sex, smoking, low vitamin D levels caused by insufficient sun exposure and/or dietary intake, and Epstein-Barr virus (EBV) infection - strong evidence now supports obesity during adolescence as a factor increasing MS risk. Organic solvents and shift work have also been reported to confer increased risk of the disease, whereas factors such as use of nicotine or alcohol, cytomegalovirus infection and a high coffee consumption are associated with a reduced risk. Certain factors - smoking, EBV infection and obesity - interact with HLA risk genes, pointing at a pathogenetic pathway involving adaptive immunity. All of the described risk factors for MS can influence adaptive and/or innate immunity, which is thought to be the main pathway modulated by MS risk alleles. Unlike genetic risk factors, many environmental and lifestyle factors can be modified, with potential for prevention, particularly for people at the greatest risk, such as relatives of individuals with MS. Here, we review recent data on environmental and lifestyle factors, with a focus on gene-environment interactions.

The Standards of Reporting of Neurological Disorders (STROND) checklist: Application to multiple sclerosis

Background:

Descriptive epidemiological studies documenting the incidence and prevalence of multiple sclerosis (MS) and studies that report morbidity, mortality, and economic burden provide essential information for patients, healthcare providers, and policymakers. However, the quality of reporting of observational studies is often poor, limiting the ability to evaluate the validity of the findings. The Standards of Reporting of Neurological Disorders (STROND) reporting guideline comprises recommendations and a 15-item checklist of reporting items to aid high-quality reporting of incidence and prevalence studies of neurological disorders.

Methods:

We explain the basic reporting items of the STROND checklist for the methods, results, and discussion sections in the context of the MS literature and searched for examples of good reporting of those items.

Results:

We identified examples of good reporting of the basic reporting items from previous systematic reviews of the descriptive epidemiologic literature in MS.

Conclusion:

The adoption of the STROND reporting guidelines should improve the quality of reporting of descriptive epidemiological studies in MS. Along with efforts to improve methodological aspects of epidemiological studies and harmonization of data collection efforts, improved reporting could contribute to furthering our understanding of the epidemiology of MS.

Prevalence of multiple sclerosis in Iranian emigrants: review of the evidence

Iran has the highest prevalence of multiple sclerosis (MS) in the Middle East and Asia. Rate of emigration has been significantly raised among Iranians and though, multiple studies have been published on prevalence of MS among Iranian emigrants. Here we systematically reviewed these publications. We performed a comprehensive literature search was performed on April 30, 2015 in data bases of MEDLINE, EMBASE, Scopus and Google Scholar for the terms 'multiple sclerosis', 'incidence', 'prevalence', 'epidemiology', 'migration', 'emigrant', 'immigrant', 'Iran', 'Parsis' and 'Persian'. Study location, prevalence day or period, and age of at disease onset were recorded for all the included publications. Nine publications from Sweden, Canada, Norway, UK, and India were included. Only three reported age-adjusted prevalence and six reported age of disease onset. MS prevalence among Iranian emigrants varied from 21 per 100,000 people in Bombay, India in 1985 to 433 per 100,000 people in British Columbia, Canada in 2012. Five studies reported the prevalence in the region of interest, ranging from 1.33 in Bombay, India to 240 in British Columbia, Canada. Five studies also reported the prevalence of MS in the population of the destination country, and in all of them, the prevalence of MS was higher in Iranian immigrants compared to native people. Prevalence studies performed in Iran and also on Iranian emigrants indicate roles for both genetic and environmental factors in MS susceptibility. Data might indicate that living in a high-risk area increases the susceptibility to MS.

Socio-economic factors and immigrant population studies of multiple sclerosis

The uneven geographical distribution of multiple sclerosis (MS) and the differences in disease severity observed between different ethnic groups indicate a complex interplay between genetic and environmental risk factors involved in the disease pathogenesis. Changes in MS risk after migration suggest influence of environmental factors on disease susceptibility. Whether the risk of MS is affected by socio-economic status (SES) is still controversial. In the present review, the combined knowledge from studies of migration and SES in MS is discussed.

Comments on the review article 'Time trends in the incidence and prevalence of multiple sclerosis in Norway during eight decades'

This article is a commentary to the Review article by Grytten et al, published in Supplement 132:29–36 (DOI: 10.1111/ane.12428).

Microbiota, immunoregulatory old friends and psychiatric disorders

Regulation of the immune system is an important function of the gut microbiota. Increasing evidence suggests that modern living conditions cause the gut microbiota to deviate from the form it took during human evolution. Contributing factors include loss of helminth infections, encountering less microbial biodiversity, and modulation of the microbiota composition by diet and antibiotic use. Thus the gut microbiota is a major mediator of the hygiene hypothesis (or as we prefer, "Old Friends" mechanism), which describes the role of organisms with which we co-evolved, and that needed to be tolerated, as crucial inducers of immunoregulation. At least partly as a consequence of reduced exposure to immunoregulatory Old Friends, many but not all of which resided in the gut, high-income countries are undergoing large increases in a wide range of chronic inflammatory disorders including allergies, autoimmunity and inflammatory bowel diseases. Depression, anxiety and reduced stress resilience are comorbid with these conditions, or can occur in individuals with persistently raised circulating levels of biomarkers of inflammation in the absence of clinically apparent peripheral inflammatory disease. Moreover poorly regulated inflammation during pregnancy might contribute to brain developmental abnormalities that underlie some cases of autism spectrum disorders and schizophrenia. In this chapter we explain how the gut microbiota drives immunoregulation, how faulty immunoregulation and inflammation predispose to psychiatric disease, and how psychological stress drives further inflammation via pathways that involve the gut and microbiota. We also outline how this two-way relationship between the brain and inflammation implicates the microbiota, Old Friends and immunoregulation in the control of stress resilience.

Prevalence of multiple sclerosis among immigrants in Norway

BACKGROUND

Multiple sclerosis (MS) prevalence is unevenly distributed worldwide. Immigration to Norway from countries with a lower MS prevalence is increasing. The aim of this study was to investigate MS prevalence in different immigrant populations in Norway and evaluate the effect of migrating from low- to high-risk regions of MS.

METHOD

First- and second-generation immigrants from the largest immigrant populations were identified from the 2012 Norwegian prevalence study. Prevalence of MS in different ethnic groups was compared using the standardized prevalence ratio (SPR).

RESULTS

European and North-American immigrants had the highest prevalence of MS, whereas African and Asian immigrants had the lowest. The prevalence of first-generation Iranian immigrants was not significantly different from the total Norwegian population (SPR 0.70, 95% CI: 0.46-1.03). Second-generation immigrants from Pakistan (SPR 1.62, 95% CI: 0.88-2.76) had a strong increase in prevalence compared to the first generation (SPR 0.13, 95% CI: 0.05-0.28).

CONCLUSION

MS prevalence among immigrants in Norway in general reflects the uneven distribution worldwide. The sharp increase in prevalence in immigrants seen in one generation suggests strong environmental factors affecting the MS risk in Norway.

Multiple sclerosis in the Iranian immigrant population of BC, Canada: prevalence and risk factors

Background:

There is a well-documented increase in the risk of multiple sclerosis (MS) when migrating from a region of low prevalence to one of high prevalence.

Objective:

We present here an investigation of MS prevalence and candidate environmental and genetic risk factors among Iranian immigrants to British Columbia (BC), Canada.

Methods:

MS cases of Iranian ancestry were ascertained from a population-based Canadian study. We collected blood samples for genetic and serological analyses, and administered a personal history questionnaire to the cases.

Results:

The crude prevalence of MS in this population of Iranian ancestry was 287/100,000 (95% CI: 229 – 356/100,000). MS cases were more likely to have a history of infectious mononucleosis (odds ratio (OR) = 7.5; p = 0.005) and smoking (OR = 17.0; p < 0.0001), as compared to healthy controls from previous studies in Iran. Cases were also more likely than controls to have been born between April and September (OR = 2.1; p = 0.019).

Conclusion:

The prevalence of MS among Iranian immigrants to Canada is greater than the overall prevalence of MS in Iran by a factor of at least four, and is similar to that recently observed among Iranian immigrants in other western nations. No major genetic susceptibility variants were identified, suggesting the environment in Canada may be what is increasing the risk of MS in this population.

Impact of pregabalin treatment on synaptic plasticity and glial reactivity during the course of experimental autoimmune encephalomyelitis

BACKGROUND

Multiple sclerosis (MS) is an autoimmune and neurodegenerative disease that affects young adults. It is characterized by generating a chronic demyelinating autoimmune inflammation in the central nervous system. An experimental model for studying MS is the experimental autoimmune encephalomyelitis (EAE), induced by immunization with antigenic proteins from myelin.

AIMS

The present study investigated the evolution of EAE in pregabalin treated animals up to the remission phase.

METHODS AND RESULTS

The results demonstrated a delay in the onset of the disease with statistical differences at the 10th and the 16th day after immunization. Additionally, the walking track test (CatWalk) was used to evaluate different parameters related to motor function. Although no difference between groups was obtained for the foot print pressure, the regularity index was improved post treatment, indicating a better motor coordination. The immunohistochemical analysis of putative synapse preservation and glial reactivity revealed that pregabalin treatment improved the overall morphology of the spinal cord. A preservation of circuits was depicted and the glial reaction was downregulated during the course of the disease. qRT-PCR data did not show immunomodulatory effects of pregabalin, indicating that the positive effects were restricted to the CNS environment.

CONCLUSIONS

Overall, the present data indicate that pregabalin is efficient for reducing the seriousness of EAE, delaying its course as well as reducing synaptic loss and astroglial reaction.

Regulation of the immune system by biodiversity from the natural environment: an ecosystem service essential to health

Epidemiological studies suggest that living close to the natural environment is associated with long-term health benefits including reduced death rates, reduced cardiovascular disease, and reduced psychiatric problems. This is often attributed to psychological mechanisms, boosted by exercise, social interactions, and sunlight. Compared with urban environments, exposure to green spaces does indeed trigger rapid psychological, physiological, and endocrinological effects. However, there is little evidence that these rapid transient effects cause long-term health benefits or even that they are a specific property of natural environments. Meanwhile, the illnesses that are increasing in high-income countries are associated with failing immunoregulation and poorly regulated inflammatory responses, manifested as chronically raised C-reactive protein and proinflammatory cytokines. This failure of immunoregulation is partly attributable to a lack of exposure to organisms ("Old Friends") from mankind's evolutionary past that needed to be tolerated and therefore evolved roles in driving immunoregulatory mechanisms. Some Old Friends (such as helminths and infections picked up at birth that established carrier states) are almost eliminated from the urban environment. This increases our dependence on Old Friends derived from our mothers, other people, animals, and the environment. It is suggested that the requirement for microbial input from the environment to drive immunoregulation is a major component of the beneficial effect of green space, and a neglected ecosystem service that is essential for our well-being. This insight will allow green spaces to be designed to optimize health benefits and will provide impetus from health systems for the preservation of ecosystem biodiversity.

Microbial 'Old Friends', immunoregulation and stress resilience

Chronic inflammatory diseases (autoimmunity, allergy and inflammatory bowel diseases) are increasing in prevalence in urban communities in high-income countries. One important factor is reduced exposure to immunoregulation-inducing macro- and microorganisms and microbiota that accompanied mammalian evolution (the hygiene hypothesis or 'Old Friends' mechanism). Reduced exposure to these organisms predisposes to poor regulation of inflammation. But inflammation is equally relevant to psychiatric disorders. Inflammatory mediators modulate brain development, cognition and mood, and accompany low socioeconomic status and some cases of depression in developed countries. The risk of all these conditions (chronic inflammatory and psychiatric) is increased in urban versus rural communities, and increased in immigrants, particularly if they move from a low- to a high-income country during infancy, and often the prevalence increases further in second generation immigrants, suggesting that critical exposures modulating disease risk occur during pregnancy and infancy. Diminished exposure to immunoregulation-inducing Old Friends in the perinatal period may enhance the consequences of psychosocial stressors, which induce increased levels of inflammatory mediators, modulate the microbiota and increase the risk for developing all known psychiatric conditions. In later life, the detrimental effects of psychosocial stressors may be exaggerated when the stress occurs against a background of reduced immunoregulation, so that more inflammation (and therefore more psychiatric symptoms) result from any given level of psychosocial stress. This interaction between immunoregulatory deficits and psychosocial stressors may lead to reduced stress resilience in modern urban communities. This concept suggests novel interpretations of recent epidemiology, and novel approaches to the increasing burden of psychiatric disease.

From the Gothenburg cohort to the Swedish multiple sclerosis registry

An overview of prevalence and incidence studies performed in Swedish centres is provided, showing improving coverage and methodology, notably the development in Gothenburg of the representative incidence cohort design. A common database for major Swedish centres was established in 1995, implementing the terminology of predictors from the Gothenburg cohort. By 2001, these databases were merged into the web-based national multiple sclerosis (MS) registry, which has had an ever-increasing coverage, although with still moderate data density. The registry now contains records on 13,000 Swedish patients with MS. It has the status of a national quality registry and exerts nation-wide pharmacological surveillance. In addition, it has been, and is being, used in nearly 100 scientific studies, including large epidemiological and genetic projects.