Increasing prevalence and incidence of multiple sclerosis in northern Japan

Islands and Neurology: An Exploration into a Unique Association

The current study investigates the intricate connection between neurology and islands shedding light on the historical, epidemiological, and genetic aspects. Based on an elaborate literature review, we identified neurological conditions having a significant clustering in an island(s), confined to a particular island(s), named after an island, and described first in an island. The genetic factors played a crucial role, uncovering disorders like Cayman ataxia, Machado Joseph disease, SGCE-mediated dystonia-myoclonus syndrome, X-linked dystonia parkinsonism, hereditary transthyretinrelated amyloidosis, Charcot Marie Tooth 4F, and progressive myoclonic epilepsy syndromes, that exhibited remarkable clustering in diverse islands. Local customs also left enduring imprints. Practices such as cannibalism in Papua New Guinea led to Kuru, while cycad seed consumption in Guam triggered Lytico-Bodig disease. Toxin-mediated neurologic disorders exhibited intricate island connections, exemplified by Minamata disease in Kyushu islands and atypical parkinsonism in French Caribbean islands. Additionally, the Cuban epidemic of amblyopia and neuropathy was associated with severe nutritional deficiencies. This study pioneers a comprehensive review narrating the genetic, environmental, and cultural factors highlighting the spectrum of neurological disorders in island settings. It enriches the medical literature with a unique understanding of the diverse influences shaping neurological health in island environments.

The prevalence and incidence of multiple sclerosis over the past 20 years in northern Japan

OBJECTIVES

The prevalence of multiple sclerosis (MS) in East Asia is thought to be lower than in Western countries. Globally, there is a trend of increasing MS prevalence. We investigated the changes in the prevalence and clinical phenotype of MS in the Tokachi province of Hokkaido in northern Japan, from 2001 to 2021.

METHODS

Data processing sheets were sent to all related institutions inside and outside the Tokachi area of Hokkaido island in Japan and were collected from April to May 2021. The prevalence according to the Poser's diagnostic criteria for MS was determined on March 31, 2021.

RESULTS

In 2021, the crude MS prevalence in northern Japan was 22.4/100,000 (95% confidence interval, 17.6-28.0). The prevalences of MS standardized by the Japanese national population in 2001, 2006, 2011, 2016, and 2021 were 6.9, 11.5, 15.3, 18.5, and 23.3, respectively. The female/male ratio was 4.0 in 2021, increased from 2.6 in 2001. We checked the prevalence using the 2017 revised McDonald criteria, and found only additional male patient who had not fulfilled Poser's criteria. The age- and sex-adjusted incidence of MS per 100,000 individuals increased from 0.09 in 1980-1984 to 0.99 in 2005-2009; since then, it has remained stable. The proportions of primary-progressive, relapsing-remitting, and secondary-progressive MS types in 2021 were 3%, 82%, and 15%, respectively.

CONCLUSION

Our results demonstrated a consistent increase in the prevalence of MS among the northern Japanese over 20 years, particularly in females, and consistently lower rates of progressive MS in northern Japan than elsewhere in the world.

Global, regional, and national burden of multiple sclerosis from 1990 to 2019: Findings of global burden of disease study 2019

BACKGROUND

The global rising prevalence and incidence of multiple sclerosis (MS) has been reported during the past decades. However, details regarding the evolution of MS burden have not been fully studied. This study aimed to investigate the global, regional, and national burden and temporal trends in MS incidence, deaths, and disability-adjusted life years (DALYs) from 1990 to 2019 using the age-period-cohort analysis.

METHODS

We performed a secondary comprehensive analysis of incidence, deaths, and DALYs of MS by calculating the estimated annual percentage change from 1990 to 2019 obtained from the Global Burden of Disease (GBD) 2019 study. The independent age, period, and birth cohort effects were evaluated by an age-period-cohort model.

RESULTS

In 2019, there were 59,345 incident MS cases and 22,439 MS deaths worldwide. The global number of incidences, deaths, and DALYs of MS followed an upward trend, whereas the age-standardized rates (ASR) slightly declined from 1990 to 2019. High socio-demographic index (SDI) regions had the highest ASR of incidences, deaths, and DALYs in 2019, while the rate of deaths and DALYs in medium SDI regions are the lowest. Six regions which include high-income North America, Western Europe, Australasia, Central Europe, and Eastern Europe had higher ASR of incidences, deaths, and DALYs than other regions in 2019. The age effect showed that the relative risks (RRs) of incidence and DALYs reached the peak at ages 30-39 and 50-59, respectively. The period effect showed that the RRs of deaths and DALYs increased with the period. The cohort effect showed that the later cohort has lower RRs of deaths and DALYs than the early cohort.

CONCLUSION

The global cases of incidence, deaths, and DALYs of MS have all increased, whereas ASR has declined, with different trends in different regions. High SDI regions such as European countries have a substantial burden of MS. There are significant age effects for incidence, deaths, and DALYs of MS globally, and period effects and cohort effects for deaths and DALYs.

[Epidemiology of neuromyelitis optica spectrum disorder]

Neuromyelitis optica spectrum disorder (NMOSD) is a group of rare and mostly severe autoimmune demyelinating central nervous system disorders which prevalence is 0.7-1 per 100.000 population and incidence is 0.037-0.73 per 100.000 person-years. NMOSD may present as a combination of uni- or bilateral optic neuritis, transverse myelitis or lesions of brain stem and other brain regions. The symptoms are mostly relapsing (up to 97.5%) and progressive. Occurrence of relapses is associated with seropositivity for aquaporin-4 (up to 80% of NMOSD patients) and bears a less favorable prognosis (mortality up to 32%). Women seropositive for aquaporin 4 constitute 90% of NMOSD patients. Compared to other demyelinating disorders, NMOSD is characterized by late onset (mean age is about 39 years) and association with other autoimmune disorders, including systemic lupus erythematosus, myasthenia gravis and Sjogren's syndrome. A genetic predisposition was found among Blacks and Asians, with HLA-DRB1*03:01 gene associated with higher risk of NMOSD in Asians. The course of the disease tends to be more severe in Blacks. There are clusters of an increased incidence of NMOSD in the Carribeans and in the Far East. Continued increase of prevalence and incidence of NMOSD worldwide compels continued epidemiological research in order to provide early diagnosis and treatment for this disorder.

Joinpoint Regression Analysis of Trends in Multiple Sclerosis Incidence in Kuwait: 1980-2019

BACKGROUND

Multiple sclerosis (MS) is a chronic inflammatory demyelinating and neurodegenerative disease of the central nervous system with unknown precise etiology. Temporally, a tendency for increasing MS incidence has been recorded worldwide. This cross-sectional cohort study sought to quantify trends in the age-standardized incidence rates (ASIRs) (per million person-years) of MS in Kuwait from 1980 to 2019, overall and by subcohorts defined by age at MS onset, sex, and nationality.

METHODS

MS incidence data from 1980 to 2019 were obtained from the Kuwait National MS Registry (KNMSR). Using midyear relevant Kuwait population as denominator and the World Standard Population as a reference, MS ASIRs overall and by subcohorts defined by age at onset (0-19, 20-39, and 40+ years), sex (male and female), and nationality (Kuwaiti and non-Kuwaiti) were computed. Joinpoint regression analysis was conducted to estimate average annual percent change (AAPC) and its 95% confidence interval (CI) overall and by subcohorts.

RESULTS

During 1980-2019, a total of 1,764 MS incident cases of 95.6 million person-years at-risk were diagnosed and registered in KNMSR. The overall MS ASIR (per million person-years) during the study period was 34.1 (95% CI: 16.1, 52.1). Between 1980 and 2010, in the total cohort, ASIRs of MS significantly increased by 13% (AAPC = 13.0; 95% CI: 10.8, 15.3; p < 0.001), followed by statistically nonsignificant declining trend during the ensuing period (AAPC = -3.8; 95% CI: -14.8, 8.8; p = 0.522). Joinpoint regression analysis revealed that 2 subcohorts of Kuwaiti females each with one joinpoint had significant increasing trends in MS ASIRs (0- to 19-year-old Kuwaiti females, AAPC: 1980-2009, 81.0; 95% CI: 58.2, 107.0; p = 0.001; 20- to 39-year-old Kuwaiti females, AAPC: 1980-1999, 131.7; 95% CI: 26.9, 322.8; p = 0.021). Additionally, of remaining 10, 6 subcohorts had significantly (p < 0.05) increasing trends in MS ASIRs from 1980 to 2019.

CONCLUSIONS

From 1980 to 2010, Kuwait has an overall significantly increasing trend in MS ASIRs followed by a nonsignificant declining drift in the ensuing period. The increasing trend in MS risk appeared to be driven by increased risk among Kuwaiti females younger than 40 years. The underlying factors modulating MS risk in Kuwait need further studies.

Age and sex-adjusted incidence and yearly prevalence of multiple sclerosis (MS) in Mazandaran province, Iran: An 11-years study

INTRODUCTION

The incidence rate of MS is a valuable indicator of the recent changes in the risk of this disease, and it is widely implicated for health planning purposes.

OBJECTIVES

This study aims to determine the MS incidence over the past eleven years in Mazandaran province and to compare it with the other parts of Iran and the world.

MATERIALS AND METHODS

This retrospective study is conducted in Mazandaran province by using registered data in the files of the patients with their consent. The yearly crude incidence rates, age, and sex-specific incidence rates and directly standardized incidence rates of this population are calculated, and the temporal changes in the incidence rates are analyzed.

RESULTS

662 (26%) male patients with the mean (SD) age of 32.6 (9.48) and 1884 (74%) female patients with the mean (SD) age of 31.9 (9.15) are studied. The direct standardized incidence rate of MS was 3.28 in 100.000 in 2008 and reached 4.17 in 100.000 in 2018, and this increase was significant (p<0.05). Also, the yearly prevalence of MS increased from 24.4 to 72.5 in this period.

CONCLUSIONS

The MS incidence has increased in Mazandaran. The potential role of some genetic or environmental factors needs further investigation.

The changing course of multiple sclerosis: rising incidence, change in geographic distribution, disease course, and prognosis

PURPOSE OF REVIEW

This review provides a brief update of new research findings on the changing epidemiology, disease course, and prognosis of multiple sclerosis (MS).

RECENT FINDINGS

Evidence not only continues to support the female predominance in incidence and prevalence of the disease but also supports an increase in incidence of MS in geographic areas that were previously considered to be low incidence for the disease.

SUMMARY

An increased interest in population-based registries and databases will provide more valid epidemiological measures and observational studies conducted in well-defined study populations. Such studies are crucial for an accurate description of both changing prognosis of MS and differential characteristics of the various MS phenotypes.

Cell death and mitochondrial dysfunction induced by the dietary non-proteinogenic amino acid L-azetidine-2-carboxylic acid (Aze)

In addition to the 20 protein amino acids that are vital to human health, hundreds of naturally occurring amino acids, known as non-proteinogenic amino acids (NPAAs), exist and can enter the human food chain. Some NPAAs are toxic through their ability to mimic protein amino acids and this property is utilised by NPAA-containing plants to inhibit the growth of other plants or kill herbivores. The NPAA L-azetidine-2-carboxylic acid (Aze) enters the food chain through the use of sugar beet (Beta vulgaris) by-products as feed in the livestock industry and may also be found in sugar beet by-product fibre supplements. Aze mimics the protein amino acid L-proline and readily misincorporates into proteins. In light of this, we examined the toxicity of Aze to mammalian cells in vitro. We showed decreased viability in Aze-exposed cells with both apoptotic and necrotic cell death. This was accompanied by alterations in endosomal-lysosomal activity, changes to mitochondrial morphology and a significant decline in mitochondrial function. In summary, the results show that Aze exposure can lead to deleterious effects on human neuron-like cells and highlight the importance of monitoring human Aze consumption via the food chain.

Prevalence of multiple sclerosis in an urban population of Sivas province in Turkey

Background/aim

Multiple sclerosis (MS) is a common neurological disorder that can be a leading cause of nontraumatic disability in several countries. Recent reports have indicated a moderate to high risk of MS in European countries. In this study, we examined the prevalence of MS in a well-defined urban population of provincial center in Sivas Province in Turkey.

Materials and methods

This study sampled all registered residents of urban areas of provincial center in Sivas Province in April 2017 and 2018 January. All the included patients met the McDonald 2010 criteria. Medical records were reviewed, including all available previously acquired magnetic resonance imaging data. All patients were subsequently subjected to neurologic examination to confirm the MS diagnosis.

Results

We identified 21 possible MS patients, with MS diagnosis confirmed in 19. The prevalence of MS was 288 per 100,000 inhabitants.

Conclusion

For future studies, these high ratio results can be used in regional and national comparisons to determine cofactors contributing to the high prevalence of MS in our region and can help health-decision makers to better plan healthcare policies to improve neurological services and awareness about multifaceted clinical presentations of MS.

Multiple Sclerosis in the Asia Pacific Region: A Systematic Review of a Neglected Neurological Disease

Background: Multiple sclerosis is thought to be relatively uncommon in the Asia Pacific region with prevalence estimated between 0 and 20 per 100,000. There is reason to doubt these estimates due to the lack of data from many countries and the growing evidence of variability in prevalence across small geographic areas. This study was conducted to systematically review the population prevalence, incidence, mortality and disability progression estimates of MS within the Asia Pacific region. Methods: The systematic review was conducted on articles from 1985 till 31st July 2017 within the PubMed/MEDLINE, EMBASE, SCOPUS, and The Cochrane Library databases. The review included articles that were population-based studies conducted on patients with MS in the Asia Pacific region that reported either incidence, prevalence, mortality, or disease progression. Hospital-based studies and non-research articles were excluded to ensure that only information representative of the population was included for analysis. Data appraisal and extraction was done by independent reviewers. This review was registered with PROSPERO (ID: CRD42017082760). Findings: Of the 2,757 articles found, 16 studies were included. Information on 6 (18.75%) of 32 Asia Pacific countries was found, with data representing 8% of the total population. Prevalence estimates were available for 6 countries while estimates for incidence (3 countries), mortality (4 countries), and disease progression (2 countries) were limited. Interpretation: The lack of epidemiological data available in the Asia Pacific region creates a blind spot in the surveillance of MS which obscures the true burden of MS, causing patients to struggle to receive the resources and funding that they need.

Treatment and comorbidities of multiple sclerosis in an employed population in Japan: analysis of health claims data

Aim: Use real-world data to investigate the treatment, comorbidities and prevalence of multiple sclerosis (MS) in an employed Japanese population. Methods: Data from the Japanese Medical Data Center health insurance claims database were analyzed (January 2005–November 2014). Patients with claims associated with an MS diagnosis were identified (n = 494) and comorbidities and prescribed treatments were investigated. MS prevalence within the database was calculated for each calendar year (2011–2013) Results: IFN-β and prednisolone were the most commonly prescribed treatments. Common comorbidities included astigmatism and gastric ulcer. Within the database, MS prevalence increased from 0.015 to 0.016%. Conclusion: MS prevalence increased from 2011 to 2013. Some comorbidities were considered unrelated to MS owing to how physicians use disease codes for reimbursement.

The burden of multiple sclerosis in Japan

AIMS

Multiple sclerosis (MS) is a disabling autoimmune disease affecting the central nervous system. Few studies have examined the effect of MS on patient outcomes in Japan. The study aim was to quantify MS burden in Japan by comparing MS respondents to matched controls on patient outcomes.

MATERIALS AND METHODS

Data from seven administrations of the nationally representative Japan National Health and Wellness Survey (2009-2014 and 2016) were used (n = 181,423). Respondents self-reporting MS diagnosis were compared with respondents not reporting MS. Matched controls were selected using propensity scores. Respondents with MS and matched controls were compared on health-related quality-of-life (HRQoL), work productivity and activity impairment, healthcare resource utilization, and costs. Comparisons were made using Chi-square tests or one-way ANOVAs.

RESULTS

A total of 96 respondents with MS and 480 matched controls were included in the analyses. MS respondents reported worse mental (44.35 vs 47.51, p < .05), physical (33.11 vs 49.04, p < .001), and role (37.78 vs 47.11, p < .001) component summary scores (minimally important difference is 3.0). Additionally, MS respondents reported decrements on every health profile sub-scale (p < .001) and 5-Level EuroQoL-5 Dimensions outcome (p < .01). MS respondents also reported more healthcare provider visits (13.78 vs 6.13) and hospitalizations (3.02 vs 0.70; both, p < .001), leading to higher direct costs. For work productivity and activity impairment, MS respondents reported more absenteeism (17.50% vs 5.57%), presenteeism (38.11% vs 21.62%), overall work impairment (46.68% vs 25.27%), and activity impairment (46.88% vs 24.90%, all, p < .001), leading to higher indirect costs.

LIMITATIONS

Japan NHWS data are cross-sectional, and causal relationships cannot be established. Due to the self-reported nature of the data, responses could not be independently verified.

CONCLUSIONS

Results suggest MS in Japan is associated with poorer HRQoL and greater work and activity impairment, healthcare resource use, and costs. Improved MS management could benefit both patients and society.

Prevalence and clinical features of neuromyelitis optica spectrum disorders in northern Japan

Objective:

To clarify the prevalence and clinical characteristics of neuromyelitis optica spectrum disorders (NMOSD) in Japan and compare them with those in other ethnic populations.

Methods:

Data processing sheets were sent to all related institutions in northern Japan and were collected from April to May 2016. Prevalence was determined on March 31, 2016, using the 2015 International Panel for NMO Diagnosis criteria.

Results:

The crude prevalence was 4.1/100,000 (95% confidence interval 2.2–6.9) for NMOSD in northern Japan, with a significantly higher number of female than male patients (female: male 12:2). The positivity for anti-aquaporin-4 antibody was 78.6%, and the mean age at onset was 45.2 years. All patients were subjected to preventive therapy in the form of treatment with steroids or immunosuppressive agents.

Conclusions:

Our results showed that the prevalence of NMOSD in the Japanese population is similar to that in Caucasians.

Impact of combined sodium chloride and saturated long-chain fatty acid challenge on the differentiation of T helper cells in neuroinflammation

BACKGROUND

There has been a marked increase in the incidence of autoimmune diseases like multiple sclerosis (MS) in the last decades which is most likely driven by a change in environmental factors. Here, growing evidence suggests that ingredients of a Western diet like high intake of sodium chloride (NaCl) or saturated fatty acids may impact systemic immune responses, thus increasing disease susceptibility. Recently, we have shown that high dietary salt or long-chain fatty acid (LCFA) intake indeed aggravates T helper (Th) cell responses and neuroinflammation.

METHODS

Naïve CD4⁺ T cells were treated with an excess of 40 mM NaCl and/or 250 μM lauric acid (LA) in vitro to analyze effects on Th cell differentiation, cytokine secretion, and gene expression. We employed ex vivo analyses of the model disease murine experimental autoimmune encephalomyelitis (EAE) to investigate whether salt and LCFA may affect disease severity and T cell activation in vivo.

RESULTS

LCFA, like LA, together with NaCl enhance the differentiation of Th1 and Th17 cells as well as pro-inflammatory cytokine and gene expression in vitro. In cell culture, we observed an additive effect of LA and hypertonic extracellular NaCl (NaCl + LA) in Th17 differentiation assays as well as on IL-17, GM-CSF, and IL-2 gene expression. In contrast, NaCl + LA reduced Th2 frequencies. We employed EAE as a model of Th1/Th17 cell-mediated autoimmunity and show that the combination of a NaCl- and LA-rich diet aggravated the disease course and increased T cell infiltration into the central nervous system (CNS) to the same extent as dietary NaCl.

CONCLUSIONS

Our findings demonstrate a partially additive effect of NaCl and LA on Th cell polarization in vitro and on Th cell responses in autoimmune neuroinflammation. These data may help to better understand the pathophysiology of autoimmune diseases such as MS.

Prevalence, treatments and medical cost of multiple sclerosis in Japan based on analysis of a health insurance claims database

Objective

To understand, through an analysis of health insurance claims data, the current treatment status and medical cost of multiple sclerosis (MS) in Japan.

Methods

We analyzed claims data (January 2005-January 2016) from the Japan Medical Data Center Co., Ltd., identifying MS patients, except those with neuromyelitis optica, using an algorithm based on diagnosis codes. Prescription drug usage and medical costs for MS patients were analyzed.

Results

A total of 713 MS patients were identified in the database. Between 2011 and 2015, the age-adjusted prevalence of MS in the database increased from 0.015% to 0.019%, and the female-to-male ratio increased from 1.70 to 2.03. The prescription rate for disease-modifying therapy drugs was higher in larger care settings. Prescriptions for fingolimod increased from 2011, with a concomitant decrease in prescriptions for interferon. The per patient per month cost for MS was ¥124 337 (US$1190 or €1084, as of October 2016). This was higher than the costs for Parkinson's disease (¥84 410), myasthenia gravis (¥82 944) and rheumatoid arthritis (¥53 843). However, the total per member per month cost for MS, which represents the population-based economic impact, was ¥25.2, which was lower than the parallel costs for Parkinson's disease (¥123.0) and rheumatoid arthritis (¥311.6) because of the low prevalence of MS in Japan.

Conclusions

Using real-world data, we obtained up-to-date prevalence, treatment status and medical cost information for MS in Japan. The present results showed the efficacy of a real-world database to obtain the latest national trends for rare diseases, such as MS; this could have important implications for clinicians and policymakers.

Seasonality and autoimmune diseases: The contribution of the four seasons to the mosaic of autoimmunity

Autoimmune diseases (ADs) are a heterogeneous groups of diseases that occur as a results of loss of tolerance to self antigens. While the etiopathogeneis remain obscure, different environmental factors were suggested to have a role in the development of autoimmunity, including infections, low vitamin D levels, UV radiation, and melatonin. Interestingly, such factors possess seasonal variation patterns that could influence disease development, severity and progression. Vitamin D levels which reach a nadir during late winter and early spring is correlated with increased disease activity, clinical severity as well as relapse rates in several disease entities including multiple sclerosis (MS), non-cutaneous flares of systemic lupus erythematosus (SLE), psoriasis, and rheumatoid arthritis (RA). Additionally, immunomodulatory actions of melatonin secretion ameliorate the severity of several ADs including MS and SLE. Melatonin levels are lowest during spring, a finding that correlates with the highest exacerbation rates of MS. Further, melatonin is postulated to be involved in the etiopathogenesis of inflammatory bowel diseases (IBD) through it influence on adhesion molecule and therefore transcription factor expression. Moreover, infections can mount to ADs through pro-inflammatory cytokine release and human antigen mimicry. Seasonal patterns of infectious diseases are correlated with the onset and exacerbation of ADs. During the winter, increased incidence of Epstein-Barr virus (EBV) infectious are associated with MS and SLE flares/onset respectively. In addition, higher Rotavirus infections during the winter precedes type 1 diabetes mellitus onset (T1DM). Moreover, Escherichia coli (E. coli) infection prior to primary biliary cirrhosis (PBC) and T1DM disease onset subsequent to Coxachievirus infections are seen to occur during late summer, a finding that correlate with infectious agents' pattern of seasonality. In this review, the effects of seasonality on the onset, relapses and activity of various ADs were discussed. Consideration of seasonal variation patterns of ADs can possibly provide clues to diseases pathogenesis and lead to development of new approaches in treatment and preventative care.

Prevalence of Multiple Sclerosis in the Middle Black Sea Region of Turkey and Demographic Characteristics of Patients

INTRODUCTION

Multiple sclerosis (MS), a demyelinating disease of the central nervous system, is increasing in prevalence worldwide. Other than small-scale studies, there is a scarcity of data on the prevalence of MS in Turkey. The present study aimed to elucidate the prevalence of MS in the Middle Black Sea Region and the demographic characteristics of patients.

METHODS

Patients living in the Middle Black Sea Region and who were diagnosed with MS were included. The study was designed based hospital of Turkey.

RESULTS

A total of 1,787 patients were interviewed, and a diagnosis of MS was confirmed in 1,584. The prevalence of MS was found to be 43.2/100,000 in the Middle Black Sea Region; this was calculated based on the total population and number of patients in the provinces and districts in this region. The mean age at the disease onset was 29.39±7.6 years. Among the patients, 1,299 (81.9%) had relapsing-remitting MS, 74 had secondary progressive MS, 77 had relapsing-progressive MS, 47 had primary progressive MS, and 87 had clinically isolated syndrome.

CONCLUSION

The Middle Black Sea Region was found to have a high risk for the prevalence of MS. This study is the most comprehensive epidemiologic study having the largest geographical distribution on the prevalence of MS in Turkey.

Environmental factors in autoimmune diseases and their role in multiple sclerosis

An increase in autoimmune diseases poses a socioeconomic challenge worldwide. Predisposing genetic risk has been identified, yet environmental factors make up a significant part of the risk in disease initiation and propagation. Next to improved hygiene and a gross reduction of infections, changes in dietary habits are one of the most evident Western lifestyle factors potentially associated with the increase in autoimmune diseases. Growing evidence suggests that particularly a typical 'Western diet', rich in saturated fat and salt and related pathologies can have a profound impact on local and systemic immune responses under physiologic and autoimmune conditions such as in multiple sclerosis (MS). In this review, we discuss recent findings on environmental factors influencing autoimmunity with an emphasis on the impact of 'Western diet' on immune homeostasis and gut microbiota in MS.

Efficacy, safety, and pharmacokinetics of natalizumab in Japanese multiple sclerosis patients: A double-blind, randomized controlled trial and open-label pharmacokinetic study

BACKGROUND

Natalizumab, an anti-α4 integrin monoclonal antibody, has demonstrated efficacy in phase 2 and 3 studies of predominantly Caucasian patients with relapsing-remitting multiple sclerosis (RRMS).

OBJECTIVE

To evaluate the efficacy, safety, pharmacokinetics (PK), and pharmacodynamics (PD) of natalizumab in Japanese RRMS patients.

METHODS

This multicenter, phase 2 study included an open-label PK/PD study in 12 patients (part A) and a double-blind, placebo-controlled, randomized (computer-generated sequence) study in 94 patients (part B). For part B, patients received intravenous natalizumab 300mg (n=47) or placebo (n=47) every 4 weeks. The primary efficacy endpoint was the rate of development of new active lesions (gadolinium-enhancing or new/enlarging T2 lesions) over 24 weeks. Clinical relapses and safety were also assessed.

RESULTS

New active lesions developed at a significantly lower mean rate in natalizumab-treated patients (0.06 lesions/24 weeks) than in placebo-treated patients (0.35 lesions/24 weeks) (p<0.001). The annualized relapse rate was 0.53 for natalizumab and 1.73 for placebo (p<0.001). Twice as many natalizumab-treated patients (79%) as placebo-treated patients (38%) were relapse-free (p<0.001). The safety, PK, and PD profiles of natalizumab in this study were consistent with data in Caucasian RRMS patients.

CONCLUSIONS

In Japanese RRMS patients, natalizumab treatment every 4 weeks for 24 weeks was well tolerated and reduced the development of new brain lesions and relapses (Funded by Biogen; ClinicalTrials.gov identifier: NCT01440101).

Ongoing increase in incidence and prevalence of multiple sclerosis in Newcastle, Australia: A 50-year study

BACKGROUND

Since 1959, multiple sclerosis (MS) prevalence has been estimated for the east coast Australian city of Newcastle. Previous surveys, conducted in 1988 and 2003, have described an increase in the prevalence and incidence of MS.

OBJECTIVES

In this study, we evaluated whether these trends continue and provide 50 years of MS epidemiological follow-up for this southern hemisphere city.

METHODS

Expressed per 100,000 people, prevalence of MS in Newcastle was calculated for those with a confirmed diagnosis of MS on 9 August 2011 and incidence based on the number of cases with MS diagnosis made during the preceding decade. Data were age-standardised to the total Australian population. Statistical comparisons were undertaken using Poisson regression analysis.

RESULTS

In 2011, the estimate of MS prevalence was 124.2, with female-to-male ratio reaching 3.1, a 53% increase in female predominance since 1996. MS incidence increased to 6.7, with a significantly higher proportion of new female cases since the previous survey.

CONCLUSION

Prevalence of MS in Newcastle has risen linearly and is contributed to by a substantial increase in new cases over the preceding decade. Female predominance of MS cases continues to increase with a new diagnosis three times more likely in women.

Epidemiology of Multiple Sclerosis

The epidemiology of multiple sclerosis (MS) includes a consideration of genetic and environmental factors. Comparative studies of different populations have revealed prevalence and incidence rates that vary with geography and ethnicity. With a prevalence ranging from 2 per 100,000 in Japan to greater than 100 per 100,000 in Northern Europe and North America, the burden of MS is similarly unevenly influenced by longevity and comorbid disorders. Well-powered genome-wide association studies have investigated the genetic substrate of MS, providing insight into autoimmune mechanisms involved in the etiopathogenesis of MS and elucidating possible avenues of biological treatment.

Increasing prevalence of multiple sclerosis in Västerbotten County of Sweden

OBJECTIVES

To update the incidence and prevalence of multiple sclerosis (MS) in Västerbotten County, Sweden, and to compare this to previous investigations in the same area.

BACKGROUND

Northern Sweden is a high-risk area for developing MS. Västerbotten County has previously been surveyed in detail regarding the occurrence of MS. In several countries, increases in MS prevalence and incidence as well as a change in the sex ratio have been reported.

MATERIALS AND METHODS

Multiple sources were used to identify MS cases in Västerbotten that either had their onset of the disease from 1998 to 2010 and/or lived in Västerbotten, the two dates chosen for prevalence calculation: the 31st of December 2005 and 2010.

RESULTS

The mean yearly incidence of MS in Västerbotten during the entire period 1998-2010 was 6.0/100,000. The female to male ratio was 2.1. The prevalence of MS in Västerbotten was 188/100,000 on 31st of December 2005 and 215/100,000 on 31st of December 2010. The MS prevalence increased over time from 1990 to 2010.

CONCLUSIONS

The prevalence of MS in Västerbotten County has increased between 1990 and 2010, while no statistically significant increase in incidence was seen.

Incidence of Multiple Sclerosis and Related Disorders in Asian Populations of British Columbia

BACKGROUND

Global variation in the incidence of multiple sclerosis (MS) is generally ascribed to differences in genetic and environmental risk factors. Here we investigate temporal trends in the incidence of MS and related disorders in British Columbia, Canada, from 1986 to 2010, focusing particularly on the Asian ethnic subpopulation.

METHODS

A longitudinal database was screened to identify newly diagnosed cases of MS and related disorders, including neuromyelitis optica and clinically isolated syndromes. Age-standardized, sex-specific mean annual incidence was calculated for the Asian and non-Asian population of British Columbia for 5-year intervals from 1986 to 2010. Temporal changes and cohort differences in incidence rates and demographic characteristics were evaluated.

RESULTS

During this period, the incidence of MS and related disorders in the non-Asian population remained relatively unchanged, from 10.41 (95% confidence interval [CI]: 9.87-10.97) to 9.91 (95% CI: 9.46-10.39) per 100,000 (p=0.167). In contrast, incidence in the Asian population doubled during the same period. This increase was driven by a precipitous rise in the incidence of MS in females from 0.71 (95% CI: 0.01-1.50) to 2.08 (95% CI: 1.43-2.91) per 100,000 (p=0.004), including both Canadian-born and immigrant Asians. The incidence of neuromyelitis optica did not change significantly during this period.

CONCLUSIONS

The incidence of MS may be increasing among females in the Asian ethnic population of British Columbia.

The co-occurrence of multiple sclerosis and type 1 diabetes: shared aetiologic features and clinical implication for MS aetiology

We reviewed the evidence for the co-occurrence of type 1 diabetes mellitus (T1D) and multiple sclerosis (MS), and assessed the clinical significance of this association and the shared aetiological features of the two diseases. T1D and MS contribute considerably to the burden of autoimmune diseases in young adults. The co-occurrence of MS and T1D has been reported by a number of studies, suggesting that the two conditions share one or more aetiological components. Both conditions have been associated with distinct human leukocyte antigen (HLA) haplotypes but share a number of similarities in clinical, epidemiological and immunological features, leading to suggestions of possible common mechanisms of development. While underlying genetic factors may be important for the co-occurrence of both conditions, some evidence suggests that environmental factors such as vitamin D deficiency may also modulate an individual's risk for the development of both conditions. Evidence on whether the co-occurrence of the two autoimmune conditions will affect the disease course and severity of MS is merely absent. Further studies need to be conducted to ascertain whether the neuropathology associated with T1D might influence the disease course and contribute to the severity of MS.

Is it time for a new global classification of multiple sclerosis?

BACKGROUND

The geographic distribution of multiple sclerosis (MS) is classically divided into three zones based on frequency that were established by Kurtzke in the early 1970s. In recent years, an increasing number of epidemiological studies have shown significantly higher MS prevalence and incidence rates.

OBJECTIVE

The aim of this study was to review and update the geographic distribution of MS using incidence, prevalence and disease duration from the latest epidemiology surveys.

METHODS

We conducted a systematic review of articles on MS epidemiology published between January 1, 1990 and December 31, 2012.

RESULTS

MS studies were grouped by continent: the Americas, Europe, Asia, Australia/New Zealand, and Africa. A total of 101 studies were identified according to the inclusion criteria, and 58 reported incidence estimates. Globally, the median estimated incidence of MS was 5.2 (range: 0.5-20.6) per 100,000 p-yrs, the median estimated prevalence of MS was 112.0 (with a range of 5.2-335) per 100,000 p-yrs, and the average disease duration was 20.2 years (range: 7.6-36.2).

CONCLUSION

In the past few decades, the global prevalence and incidence patterns of MS have changed dramatically. Regardless of the reason of increasing prevalence and incidence rate, we suggest the need for a novel classification system based on global MS disease burden. Adopting such a system would improve economic efficiency and prioritization in health policy planning for MS.

Role of "Western diet" in inflammatory autoimmune diseases

Developed societies, although having successfully reduced the burden of infectious disease, constitute an environment where metabolic, cardiovascular, and autoimmune diseases thrive. Living in westernized countries has not fundamentally changed the genetic basis on which these diseases emerge, but has strong impact on lifestyle and pathogen exposure. In particular, nutritional patterns collectively termed the "Western diet", including high-fat and cholesterol, high-protein, high-sugar, and excess salt intake, as well as frequent consumption of processed and 'fast foods', promote obesity, metabolic syndrome, and cardiovascular disease. These factors have also gained high interest as possible promoters of autoimmune diseases. Underlying metabolic and immunologic mechanisms are currently being intensively explored. This review discusses the current knowledge relative to the association of "Western diet" with autoimmunity, and highlights the role of T cells as central players linking dietary influences to autoimmune pathology.

Increasing prevalence and incidence rates of multiple sclerosis in Kuwait

Background:

Kuwait was considered as low to intermediate risk area for MS.

Objectives:

To determine the prevalence and incidence rates of MS among Kuwaiti nationals based on 2011 population census.

Methods:

This cross-sectional study was conducted between October 2010 and April 2013 using the newly developed national MS registry in Kuwait. Patients with a diagnosis of MS according to 2010 revised McDonald criteria were identified. The crude, age- and sex-specific prevalence and incidence rates among Kuwaiti patients were calculated.

Results:

1176 MS patients were identified of which 927 (78.8%) were Kuwaitis and 249 (21.2%) were expatriates. Among Kuwaiti patients, female to male ratio was 1.8:1 with a mean age of 35.40 ± 10.99 years. The prevalence rate of MS was 85.05 per 100,000 persons (95% CI: 82.80 – 87.04). There was a peak in prevalence among patients aged 30–39 years. The incidence of MS was 6.88 per 100,000 persons (95% CI 5.52–8.55). Between 2003 and 2011, the incidence increased 3.22 and 2.54 times in women and men respectively.

Conclusion:

Kuwait is considered a high-risk area for MS. The significant increase in prevalence and incidence rates may represent a true increase despite the improvement in case ascertainment and case definition.

Burden of disease of multiple sclerosis in Korea

OBJECTIVES

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. There are few reports on the burden of disease of MS, worldwide. The authors aim to estimate burden of disease and estimate the epidemiologic indexes of MS in Korea using available epidemiologic data.

METHODS

Epidemiologic indexes were computed using DISMOD II software based on prevalence from nationwide survey, incidence estimated from extrapolation, mortality from National Statistics Office, and duration of disease from literature as input indexes. We calculated disability-adjusted life year (DALY) as a measure of premature mortality and disability, equivalent to years of healthy life lost due to a given condition.

RESULTS

The incidence of MS in Korea was 0.1 per 100,000, higher in female than in male. The highest incidence was estimated in the age group between 35 and 44 years in male and age group between 25 and 29 years in female. Total burden of disease of MS was 1,394 DALY, comprised of 292 (21%) years of life lost and 1,101 (79%) years lived with disability. The mean age at onset of MS was 33 years old in men and 32 years old in female. Estimated duration of disease was 35 years in men and 40 years in female. Most of the DALY of MS occurred in the adult population between 25 and 54 years of age.

CONCLUSION

Although MS is a rare disease in Korea, most of the DALY arises from young people, which results in a major financial burden on the patient, family, health system and society.

Anti-aquaporin-4 antibody-positive definite neuromyelitis optica in a patient with thymectomy for myasthenia gravis

BACKGROUND

Since serum anti-aquaporin-4 (AQP4) antibody/neuromyelitis optica (NMO)-IgG has been detected as a specific biomarker for NMO), new diagnostic criteria have been proposed. Recently, a rare coexistence of NMO and myasthenia gravis (MG) has been documented. Here, we provide further evidence of the association of these 2 immunologic disorders and review the literature.

CASE REPORT

A 60-year-old woman, who had a history of optic neuritis at age 43, developed longitudinally extended transverse myelitis (LETM). She had repeated optic neuritis and longitudinally extended transverse myelitis attacks, which have been treated by corticosteroid pulse therapy. She was diagnosed as having definite NMO, because serum anti-aquaporin-4 antibody was positive. She had also been suffering from generalized MG since age 30 and underwent thymectomy at age 40. There have been 14 patients with NMO associated with MG, most of whom developed NMO years after thymectomy. Our patient is the seventh patient with seropositive NMO who underwent thymectomy for MG.

CONCLUSIONS

The coexistence of MG with thymectomy and seropositive NMO suggests an etiopathogenic link between these 2 disorders but remains underrecognized by neurologists. Neurologists should consider this possible association when encountering atypical presentations of either MG or NMO.

Environmental risk factors for multiple sclerosis: a review with a focus on molecular mechanisms

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.

Increased prevalence, incidence, and female predominance of multiple sclerosis in northern Japan

OBJECTIVE

To carry out the third epidemiologic surveillance of multiple sclerosis (MS) in Tokachi province, on the northernmost island of Japan, and to compare the results of the present survey on the prevalence, incidence, and characteristics of MS and neuromyelitis optica (NMO) with those of previous surveys performed in 2001 and 2006.

METHODS

A data processing sheet was sent to all MS-related institutions in Tokachi province, and all sheets were collected in March 2011. The criteria of Poser were used for diagnosing MS and the criteria proposed by Wingerchuk for diagnosing NMO. We then compared the results of the present survey with those of previous surveys performed in 2001 and 2006 in the same community.

RESULTS

Fifty-seven patients diagnosed with MS according to the criteria of Poser were identified. The prevalence was 16.2/100,000 in 2011, which was higher than in the previous studies. The female/male ratio of MS was 2.63, 2.75, and 3.38 in 2001, 2006, and 2011, respectively. Three patients fulfilled the criteria for diagnosis of NMO in 2011; the prevalence of NMO was 0.9/100,000.

CONCLUSIONS

The results of this study suggest that the prevalence and the female predominance of MS have been increasing, due to an increase in the incidence after 1990, and that the prevalence of NMO is relatively low in northern Japan.

The Gulf War era multiple sclerosis cohort: age and incidence rates by race, sex and service

We characterize here a new nationwide incident cohort of multiple sclerosis from the US military-veteran population. This cohort provides an update to the only other US nationwide incidence study of multiple sclerosis performed during the 1970s. Medical records and data from the Department of Defense and Department of Veterans Affairs for cases of multiple sclerosis who served in the military between 1990, the start of the Gulf War era, and 2007 and who were service-connected for this disorder by the Department of Veterans Affairs from 1990 on, were reviewed. A total of 2691 patients were confirmed as having multiple sclerosis: 2288 definite, 190 possible, 207 clinically isolated syndrome and six neuromyelitis optica. Overall racial categories were White, Black and other, which included all Hispanics. There were 1278 White males and 556 females; 360 Black males and 296 females; and 200 others, 153 (77%) of whom were Hispanic. Mean age at onset of 30.7 years did not differ significantly by race or sex. Age at onset was 17-50 years in 99%, the same age range as 99% of the military. Average annual age specific (age 17-50 years) incidence rates per 100 000 for the entire series were 9.6 with 95% confidence interval of 9.3-10.0. Rates for Blacks were highest at 12.1 with confidence interval 11.2-13.1, Whites were 9.3 (interval 8.9-9.8) and others 6.9 (interval 6.0-7.9). For 83 Hispanics defined for 2000-07, the rate was 8.2 (interval 6.5-10.1). Much smaller numbers gave rates of 3.3 for Asian/Pacific Islanders and 3.1 for native Americans. Rates by sex for Whites were 7.3 and 25.8 male and female, respectively, for Blacks 8.4 and 26.3, and for Hispanics 6.6 and 17.0. Rates by service were high for Air Force (10.9) and Army (10.6), medium for Navy (9.1) and Coast Guard (7.9), and low for Marines (5.3). Relative risk of multiple sclerosis was 3.39 female:male and 1.27 Black:White. These new findings indicate that females of all races now have incidence rates for multiple sclerosis some three times those of their male counterparts and that among these groups, Blacks have the highest and others (probably including Hispanics) the lowest incidence rates regardless of sex or service. The low rate for Marines is unexplained. This Gulf War era multiple sclerosis cohort provides a unique resource for further study.

Genetic and environmental backgrounds responsible for the changes in the phenotype of MS in Japanese subjects

There are two distinct phenotypes of multiple sclerosis (MS) in Asians, manifesting as opticospinal (OSMS) and conventional (CMS) forms. In Japan, the results of four nationwide surveys of MS conducted between 1972 and 2004 have revealed a four-fold increase in the estimated number of clinically definite MS patients in 2003 compared with 1972; a shift in the peak age at onset from the early 30s in 1989 to the early 20s in 2003; a successive proportional decrease in optic-spinal involvement in clinically definite MS patients; an increase in the number of CMS patients with Barkhof brain lesions with advancing birth year and a decrease in the number of OSMS patients with LESCLs. These findings suggest that MS phenotypes are drastically altered by environmental factors such as latitude and "Westernization". Helicobacter pylori infection rates, reflecting sanitary conditions in infancy, are significantly different between CMS and OSMS patients. Both phenotypes show distinct HLA class II gene associations. Therefore, changes in environmental factors may have differentially influenced susceptibility to each disease subtype, given that disease susceptibility is only partly genetically determined.

Prevalence of multiple sclerosis: door-to-door survey in three rural areas of coastal Black Sea regions of Turkey

BACKGROUND

Little information exists on multiple sclerosis (MS) in Turkey. With a door-to-door survey in an urban part of Istanbul, we recently reported a prevalence rate of 101/100,000 population. We therefore investigated three rural areas of Turkey at the same latitude.

METHODS

The same survey methods were used for total populations of two rural areas (Kandıra and Geyve) near Istanbul, and for half the population of Erbaa, all near 40° north latitude on the Black Sea coast.

RESULTS

In Kandıra, 5 of 8 suspects were diagnosed as having MS among 8,171 screened, resulting in a prevalence rate of 61/100,000. Geyve with 7 MS cases in 17,016 screened had a prevalence of 41/100,000, and Erbaa with 15 MS cases in 28,177 screened one of 53/100,000. Together they showed a prevalence of 51/100,000. Of the 27 patients, 20 were women; 25 had definite and 2 possible MS, the former all with abnormal laboratory findings. Average ages were 30.5 years at onset and 39.1 years at diagnosis. Clinical features and course were typical of European MS.

CONCLUSION

These findings indicate that Turkey is a high-risk MS area, similar to most regions of Mediterranean Europe, where all recent increases are likely due to (undefined) environmental factors.

Multiple sclerosis prevalence in Malaga, Southern Spain estimated by the capture–recapture method

Background: Although not definitively proven, there is commonly accepted to be a latitudinal gradient in the distribution of multiple sclerosis (MS), which is more frequent in temperate zones. The European Mediterranean countries are situated in a zone of median frequency, although ever increasing figures have been noted in the last decades.

Objective: The objective of this study was to assess the current prevalence rate of MS in the province of Malaga, Southern Spain.

Methods: The capture–recapture method (CRM) uses independent sources of data and permits the number of non-registered cases of a given disease to be estimated, and by doing so, to avoid ascertainment bias.

Results: Use of this method showed the estimated prevalence rate of MS in the province of Malaga, Southern Spain, to be 125/105 (95% confidence interval: 102/105–169/105), higher than the figures published previously.

Conclusions: Although we recognize that these data need to be confirmed in further studies and in other areas of the country using a similar method, we believe this study is the first to find such high figure of prevalence, being very similar to the figures reported in recent years in other southern European countries.

Multiple sclerosis in Hispanics: a study of clinical disease expression

Background: Hispanics living with multiple sclerosis (MS) in the United States are not well defined.

Objective: To describe the clinical characteristics of MS among Hispanic Whites (HW) in Southern California with those of non-Hispanic Whites (NHW).

Methods: We performed a medical chart review to identify all cases of HW with MS ( n = 125) who were treated at our institution during a 1-year period. We also identified cases of NHW with MS (100 NHW) treated at those clinics. All HW patients were interviewed to ascertain ancestry including detailed migration history. Disease progression was assessed by ambulatory disability and defined as Expanded Disability Status Scale (EDSS) score ≥6.

Results: Compared with NHW, HW were more likely to have a relapsing–remitting form of MS and a younger age of onset (28.4 ± 0.97 years) with presenting symptoms of optic neuritis and transverse myelitis. However, overall ambulatory disability did not differ between HW and NHW. Migration to the US at age >15 years was associated with increased risk of disability in HW.

Conclusions: HW living in the USA may be at risk of developing MS at an earlier age compared with NHW. Migration history can play an important role in the management of HW with MS.

A quantitative analysis of suspected environmental causes of MS

BACKGROUND

Multiple sclerosis (MS) is a disease with purported environmental causes. Consistent correlations have been found in various settings for latitude, smoking exposure, sunlight, and vitamin D deficiency. We analysed the contribution of various environmental factors to the risk of developing MS from a population perspective.

METHODS

We collated global data of MS prevalence from 54 studies over the previous ten years and calculated the degree of risk contributed by latitude, longitude, ultraviolet radiation (from NASA satellite data and formulae for available sunlight hours), population smoking rates (from WHO data), gender, study date, study demographics, and several socioeconomic factors. We report a very significant negative correlation between MS prevalence and available ultraviolet (UV) radiation.

RESULTS

The lack of available UV radiation outweighs other factors by at least 20 fold (p < 10⁻⁸) from single variate regression analysis. Multiple regression analysis revealed that latitude and longitude are also significant factors; smoking may also provide a very minimal role. The eight prevalence studies from Scandinavia produced prevalences that were lower than expected, given their global geospatial positioning.

CONCLUSIONS

The available ultraviolet radiation is a significant environmental factor, more so than all the other factors examined.

Increasing incidence of multiple sclerosis in women in Northern Finland

Background: The geographical distribution of multiple sclerosis (MS) means that prevalence rates increase with latitude north or south of the equator. Temporally, a tendency for increased incidences of MS has been observed over the past two decades.

Objectives: Since epidemiological studies of MS in areas close to the Arctic Circle are rare, we evaluated the incidence and prevalence of MS in Northern Ostrobothnia by means of a retrospective cohort study covering the period 1992–2007.

Methods: Patients with a definite clinical diagnosis of MS based on the Poser criteria and the early McDonald criteria of 2001 were identified in the region of Northern Ostrobothnia (population 386,972) and the incidence was calculated at 1-year time intervals, both overall and by gender.

Results: The overall prevalence was 103/100,000 (95% CI, 93–113), with a female/male ratio of 2.17. The mean overall incidence was 6.3/100,000 (95% CI, 5.2–7.2). The incidence shows a tendency to increase over the 16-year period due to a pronounced rise in the female incidence.

Conclusions: Our results show a high prevalence of MS in Northern Ostrobothnia and a disproportional increase in the female MS incidence. These recent epidemiological features may be associated with environmental risk factors such as a vitamin D deficit, low life-long UV radiation and the high-latitude geographical location.

The changing demographic pattern of multiple sclerosis epidemiology

The uneven distribution of multiple sclerosis (MS) across populations can be attributed to differences in genes and the environment and their interaction. Prevalence and incidence surveys could be affected by inaccuracy of diagnosis and ascertainment, and prevalence also depends on survival. These sources of error might play a part in the geographical and temporal variations. Our literature search and meta-regression analyses indicated an almost universal increase in prevalence and incidence of MS over time; they challenge the well accepted theory of a latitudinal gradient of incidence of MS in Europe and North America, while this gradient is still apparent for Australia and New Zealand; and suggest a general, although not ubiquitous, increase in incidence of MS in females. The latter observation should prompt epidemiological studies to focus on changes in lifestyle in females. New insights into gene-environment and gene-gene interactions complicate interpretations of demographic epidemiology and have made obsolete the idea of simple causative associations between genes or the environment and MS.

Relationship between Barkhof criteria and the clinical features of multiple sclerosis in northern Japan

We previously reported that the prevalence of multiple sclerosis (MS) in the Tokachi Province of Hokkaido increased from 8.6 to 13.1 per 100,000 individuals between 2001 and 2006. Here, we study the frequency of MS patients who fulfill the Barkhof criteria and identified their common features. All 47 subjects in our previous study, who fulfilled Poser's criteria, were included in this study. Of these, 33 satisfied the Barkhof criteria. In 2006, 9.2 per 100,000 MS patients fulfilled the Barkhof criteria; the percentage of patients who fulfilled these criteria was significantly higher among patients born after 1960 than among those born before 1960 (84.3% and 40.0%, respectively). The proportion of patients with conventional MS (C-MS) who fulfilled the Barkhof criteria was higher than that of patients with opticospinal MS (OS-MS) who fulfilled these criteria (93.9% and 71.4%, respectively). Longitudinally extensive spinal cord lesions (LESCLs) were not associated with the brain lesions defined in the Barkhof criteria (Barkhof brain lesions). In Tokachi Province, the increased percentage of MS patients who fulfill the Barkhof criteria was associated with increased C-MS incidence and an increase in the proportion of C-MS patients with Barkhof brain lesions among people born after 1960.

Recent insights in the epidemiology of autoimmune diseases: improved prevalence estimates and understanding of clustering of diseases

Previous studies have estimated a prevalence of a broad grouping of autoimmune diseases of 3.2%, based on literature review of studies published between 1965 and 1995, and 5.3%, based on national hospitalization registry data in Denmark. We examine more recent studies pertaining to the prevalence of 29 autoimmune diseases, and use these data to correct for the underascertainment of some diseases in the hospitalization registry data. This analysis results in an estimated prevalence of 7.6-9.4%, depending on the size of the correction factor used. The rates for most diseases for which data are available from many geographic regions span overlapping ranges. We also review studies of the co-occurrence of diseases within individuals and within families, focusing on specific pairs of diseases to better distinguish patterns that may result in insights pertaining to shared etiological pathways. Overall, data support a tendency for autoimmune diseases to co-occur at greater than expected rates within proband patients and their families, but this does not appear to be a uniform phenomenon across all diseases. Multiple sclerosis and rheumatoid arthritis is one disease pair that appears to have a decreased chance of coexistence.

High prevalence of multiple sclerosis in the Swedish county of Värmland

Previous epidemiological studies have indicated that the county of Värmland in western Sweden may be a high-risk zone for multiple sclerosis (MS). The objective of this study was to determine the prevalence in the area. Hospital and general practice medical files were scrutinized. The diagnostic criteria of Poser were used, with 31 December 2002 as prevalence day. The prevalence was 170.07 per 100,000 inhabitants. The average annual incidence was 6.39 to 6.46 per 100,000 (1991—1995, 1996—2000). Multiple sclerosis was 2.3 times more common among women than men. There was a variation in prevalence among the 16 municipalities, however it was not statistically significant. The rates seemed highest in the southwestern part of the county, roughly similar in location to findings some 70 years earlier. When the prevalence ratios by geographical units for the county in 1933 were applied to the current prevalence, the distribution from these estimated cases differed from homogeneity with very high significance (p < 0.00001 ). In conclusion, this study supports previous reports indicating that Värmland continues to be a high-risk zone for MS and shares in the diffusion of the disease at the county level which we had presented for the country as a whole.