Faster progression to multiple sclerosis disability is linked to neuronal pathways associated with neurodegeneration: An ethnicity study

Although the causes of multiple sclerosis are largely unknown, genetic and environmental components play an important role. Geographic distribution, varying with latitude, reflects both genetic and environmental influences. We conducted a retrospective exploratory observational study to characterize the disability progression of 2396 Jewish patients with relapsing-remitting multiple sclerosis, followed at the Sheba Multiple Sclerosis Center, Tel-Aviv, Israel; 188 patients who originated in Iraq and 2207 patients who originated in northern Europe. Peripheral blood microarray gene expression analysis was performed in a subgroup of patients to identify molecular pathways associated with faster disability progression. During a follow-up period of 18.8 and 19.8 years, respectively, 51.6% of patients with an Iraqi origin progressed to moderate disability defined as expanded disability status scale (EDSS) score of 3.0 to 5.5, compared to 44.2% of patients with a northern European origin (odds ratio 1.347, 95% CI 1.0-1.815, p = 0.049). An Iraqi origin was associated with increased risk of progression to moderate disability adjusted for sex, disease duration, age at onset, and treatment with immunomodulatory drugs (hazard ratio 1.323; 95% CI, 1.049-1.668, p = 0.02), but not to severe disability defined as EDSS score > = 6.0 (i.e., walking aids are required for a distance of 100 meters, (hazard ratio 1.311; 95% CI, 0.918-1.874, p = 0.136). Gene expression analysis disclosed 98 differentially expressed genes (79 over-expressed and 19 under-expressed) between relapsing-remitting multiple sclerosis patients of Iraqi origin (N = 17) and northern European (N = 34) origin. Interestingly, this gene expression was enriched with genes related to neuronal pathways associated with morphology of axons, branching of neurites, proliferation of neocortical neurons, and formation of myelin sheath, suggesting an augmented process of neurodegeneration in relapsing-remitting multiple sclerosis patients with an Iraqi origin. The study results suggest that relapsing-remitting multiple sclerosis patients with an Iraqi origin progress faster to disability possibly due to an enhanced process of neurodegeneration.

Impact of Vitamin D Supplementation on Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease affecting a large number of people every year. The exact causal factor for this disease is unclear, but it commonly affects middle-aged women, with known triggers like stress, childbirth, infections, poor diet, lack of sleep, etc.

Many epidemiological studies have indicated that various genetic abnormalities are also critical drivers of the onset of MS. The major risk factors of MS identified include hypovitaminosis D while environmental protective factors include allele HLA DRB1 1501, obesity, Epstein-Barr virus infection, sexual hormones, and smoking.

Our article explores the correlation between the deficiency of vitamin D and the onset and progression of MS. The study uses a systematic review methodology by researching and reviewing scholarly articles exploring the topic. We conducted online searches of literature on Google Scholar and PubMed using the keywords "vitamin D deficiency" and "multiple sclerosis" and accessed the relevant secondary literature sources for review. The variables under study included vitamin D insufficiency as the dependent variable while MS was the independent variable. Causal variables included environmental, genetic, and protective factors.

We hypothesized that there is indeed a correlation between vitamin D deficiency and MS. The findings from our review indicate a strong correlation between the insufficiency of vitamin D and the onset and progression of MS. These results are essential in devising interventions to accomplish primary and secondary prevention of MS, as well as integrating vitamin D supplementation in current treatment protocols for MS.

Prevalence of Multiple Sclerosis in Rosario, Argentina

BACKGROUND

The prevalence and incidence of Multiple Sclerosis have been increasing worldwide over the last decades. Most of the publications during the last years outstand the prevalence in Europe, North America and Latin America. In Argentina, data published on this topic is scarce and most of the studies took place in Buenos Aires. In a recent publication, we reported an MS prevalence rate of 30.3/100,000 in the overall extension of Santa Fe, Argentina, and in that study, we noticed that MS seemed to be more frequent in the southern region of the province.

OBJECTIVE

In this study we aimed to estimate the prevalence of MS in Rosario (the third most populated district of Argentina), placed in the southeastern part of Santa Fe province.

METHODS

This is a population based, cross-sectional study. We studied the members of the Province´s medical Care Program, a health maintenance organization of the public-sector employees that offers medical and health services to 567,819 members in the province 163,513 of whom have permanent residence in Rosario department, being a large representative sample. The selected prevalence date was 30 June 2019. Cases of MS were detected with a thorough search in the electronic databases of affiliates, linking and aggregating datasets.

RESULTS

Seventy-nine MS cases were detected. The mean age was 47.7 (SD 13.5); female to male ratio was 3 to 1; the most frequent phenotype was relapsing-remitting (82.3%) followed by secondary-progressive (15.2%) and primary-progressive (2.5%). The crude prevalence rate of MS in Rosario as on 30 June 2019 was 48.3/100,000 inhabitants (95% CI: 48.28 - 48.35), 63.7/100,000 for females and 28.3/100,000 for males. The age-standardised MS prevalence rate was 43.4/100,000 inhabitants (95% CI:43.37 - 43.43) while the sex-standardised prevalence was estimated at 46.7/100,000 inhabitants (95% CI: 46.68 - 46.74). Making a proportional and linear projection to the total number of inhabitants, we deemed a total of 578 MS cases in Rosario, according to the 2010 census, and projected 620 cases by July 2019.

CONCLUSION

This is the first study that provides epidemiological data of MS prevalence for Rosario. It confirms that there are differences in the distribution of MS in Santa Fe that favour the aggregation of cases in the southern part of the province. It also supplies updated and relevant data on the distribution of MS in Argentina and Latin America.

Usage trend of oral drugs for multiple sclerosis patients in Argentina

INTRODUCTION

Over the past decade, numerous disease modifying drugs (DMDs) for relapsing- remitting multiple sclerosis (RRMS) have been approved in Argentina. The use of oral DMDs (oDMDs) has increased in recent years, although real-life data in our region is limited. We aimed to describe the tendency in the use of oDMDs (as first treatment option or after switch) in relationship with their approval in Argentina.

METHODS

A retrospective study in a cohort of MS patients from five Argentinian MS centers was conducted. Regarding the availability of different oDMDs in Argentina, we define three periods (P1-3): P1: 2012 - 2014; P2: 2015 - 2017 and P3: 2018 - 2020. An analysis was performed comparing between these three periods to assess the tendency for oDMDs use over time.

RESULT

The most frequently prescribed treatment as first DMD was: interferon beta 1a (40%) in P1, fingolimod (37.3%) in P2 and also fingolimod (35%) in P3. We found an increase in the use of oDMTs as initial treatment over time (P1: 17.7%, P2: 63.9% and P3: 65.0%; Chi-square = 41.9 p <0.01). We also found a tendency to increase the use of oDMTs after a first switch (P1: 45.5%, P2: 60.1% and P3 78.3%). Multivariate analysis showed that disease evolution (OR=1.06, p=0.04), and year of treatment initiation (OR=1.01 p<0.01) were independently associated with choice of oDMTs.

CONCLUSION

This study identified an increasing tendency for the use of oDMDs as initial treatment of RMS in relationship with their approval in Argentina.

Epstein-Barr virus infection as a predisposing factor for multiple sclerosis. An update from molecular biology, immunology and epidemiology

Introduction: Epstein-Barr virus is an infectious agent used to immortalize and induce polyclonal activation of B cells. It has been widely described that this virus produces changes in the cells it infects and in the immune response, and stimulates the development of autoimmune diseases.Objective: To characterize the association between Epstein-Barr virus and multiple sclerosis described in current scientific literature.Materials and methods: A 59-years range literature search was conducted in the PubMed, ScienceDirect, Redalyc and SciELO databases using the following MeSH terms: “Epstein-Barr virus, multiple sclerosis autoimmune diseases, autoimmune diseases of the nervous system”.Results: Many studies describe the association between Epstein-Barr virus and multiple sclerosis. It is believed that acute infection and viral reactivation promote the development of multiple sclerosis.Conclusions: It is necessary to conduct further research on the pathogenesis and morphophysiological and neuroimmunological changes –at the ecological, molecular, cellular, tissue, organic and systemic level– induced by the immune response and that favor the development of multiple sclerosis.

Increasing Incidence and Prevalence of Multiple Sclerosis in Puerto Rico (2013-2016)

BACKGROUND

The incidence of multiple sclerosis (MS) has been increasing worldwide over the past decades. However, this upward trend has not been examined at the country level in Latin America and the Caribbean (LAC). The aims of this study are to examine trends of MS incidence over 4 years and to provide age- and gender-standardized incidence rate estimates for a Caribbean island.

METHODS

Data from the Puerto Rico (PR) MS Foundation's registry was used to identify all newly diagnosed MS cases between 2013 and 2016. MS patients were 18 years and older and met the 2010 revised McDonald criteria. Age- and gender-standardized incidence rates were estimated.

RESULTS

A total of 583 new MS cases were diagnosed in PR from 2013 to 2016. The age- and gender-standardized MS incidence rate for PR increased from 6.1/100,000 in 2013 to 6.7/100,000 in 2016. The annual age-standardized MS incidence rates for females rose from 8.4/100,000 in 2013 to 9.8/100,000 in 2016 and were higher than males, which remained around 3.7/100,000.

CONCLUSION

Incidence estimates for PR were higher than other LAC countries but consistent with MS increases in other world regions. Our findings tend to rule out several prior potential environmental explanations for high MS incidence rates.

Environmental factors influencing multiple sclerosis in Latin America

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

Multiple sclerosis epidemiology in Latin America: An updated survey

Novel epidemiological data have appeared in recent years in Latin America (LATAM). The objective of this study was to perform an updated systematic review of the epidemiology of the disease reported in LATAM.

Incidence of Multiple Sclerosis in Puerto Rico, 2014: A Population-Based Study

BACKGROUND

Multiple sclerosis (MS) affects millions of people worldwide. The estimates for MS incidence are difficult to obtain but are important for understanding MS etiology, developing prevention strategies, and service planning. This study is aimed at estimating the 2014 incidence of MS in Puerto Rico (PR).

METHODS

The PR MS Foundation's registry was used as the data source. Neurologists, specialty pharmacies, MRI centers, health insurance companies, and the PR Department of Health identified MS cases missed by the registry. MS patients were 18 years and older and met the 2010 revised McDonald criteria. Age-standardized MS incidence rates and their corresponding 95% CIs were computed.

RESULTS

A total of 144 new MS cases were diagnosed in 2014. The age-standardized MS incidence rate was 5.1/100,000 (95% CI 4.3-5.9). The incidence rate was 7.1/100,000 (95% CI 5.7-8.5) for females and 2.9/100,000 (95% CI 2.0-3.8) for males. MS cases were mostly females (72.9%) with a mean age of 41.0 years (±1.0).

CONCLUSION

According to the country estimates, PR has a higher MS incidence than other Caribbean and Latin American countries, but a lower incidence compared to countries at higher latitudes. Our findings provide insights into the MS etiology in the Hispanic population that require additional research.

Gender ratio trends over time in multiple sclerosis patients from Argentina

Several studies in multiple sclerosis (MS) suggest a trend of increasing disease frequency in women during the last decades. A direct comparison of gender ratio trends among MS populations from Argentina remains to be carried out. The objective of the study was to compare gender ratio trends, over a 50-year span in MS populations from Argentina.

METHODS

multicenter study that included patients from 14 MS Centers of Argentina. Patients with definite MS with birth years ranging from 1940 to 1989 were included. Gender ratios were calculated by five decades based on year of birth and were adjusted for the F/M born-alive ratio derived from the Argentinean national registry of births. The F/M ratios were calculated using a multivariate logistic regression per five decades by the year of birth approach. Analyses were performed using Stata 10.1.

RESULTS

1069 patients were included. Gender ratios showed a significant increase from the first to the last decade in the whole MS sample (from 1.8 to 2.7; p value for trend=0.023). The Gender ratio did not show differences considering MS subtype.

CONCLUSION

our study showed a modest increase of the F/M ratio (from 1.8 to 2.7) over time among patients affected by MS in Argentina.

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.

Effects of sensory cueing in virtual motor rehabilitation. A review

OBJECTIVES

To critically identify studies that evaluate the effects of cueing in virtual motor rehabilitation in patients having different neurological disorders and to make recommendations for future studies.

METHODS

Data from MEDLINE®, IEEExplore, Science Direct, Cochrane library and Web of Science was searched until February 2015. We included studies that investigate the effects of cueing in virtual motor rehabilitation related to interventions for upper or lower extremities using auditory, visual, and tactile cues on motor performance in non-immersive, semi-immersive, or fully immersive virtual environments. These studies compared virtual cueing with an alternative or no intervention.

RESULTS

Ten studies with a total number of 153 patients were included in the review. All of them refer to the impact of cueing in virtual motor rehabilitation, regardless of the pathological condition. After selecting the articles, the following variables were extracted: year of publication, sample size, study design, type of cueing, intervention procedures, outcome measures, and main findings. The outcome evaluation was done at baseline and end of the treatment in most of the studies. All of studies except one showed improvements in some or all outcomes after intervention, or, in some cases, in favor of the virtual rehabilitation group compared to the control group.

CONCLUSIONS

Virtual cueing seems to be a promising approach to improve motor learning, providing a channel for non-pharmacological therapeutic intervention in different neurological disorders. However, further studies using larger and more homogeneous groups of patients are required to confirm these findings.

ENCOMS: Argentinian survey in cost of illness and unmet needs in multiple sclerosis

The objective of the study was to assess the cost of multiple sclerosis (MS) patients in Argentina categorized by disease severity using a societal perspective.

METHOD

Cross-sectional study including MS patients from 21 MS centers in 12 cities of Argentina. Patients were stratified by disease severity using the expanded disability status scale (EDSS) (group 1 with EDSS score between 0 and 3; group 2 with EDSS >3 and <7; group 3 with EDSS ≥7). Direct and indirect costs were analyzed for the second quarter of 2012 from public sources and converted to US Dollars.

RESULTS

266 patients were included. Mean annual cost per MS patient was USD 36,025 (95%CI 31,985-38,068) for patients with an EDSS between 0-3; USD 40,705 (95%CI 37,199-46,300) for patients with EDSS >3 and <7, and USD 50,712 (95%CI 47,825-62,104) for patients with EDSS ≥7.

CONCLUSIONS

This is the first Argentine study evaluating the costs of MS considering disease severity.

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.

Current and emerging treatments for relapsing multiple sclerosis in Argentinian patients: a review

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system. Recent developments have led to newer therapeutic options for disease treatment. A few studies have reported MS prevalence rates between 12 and 20 per 100,000 inhabitants nationwide in Argentina, and an incidence of 1.76 cases per 100,000 inhabitants per year. Considering the epidemiology of MS in Argentina, the total number of patients affected is estimated at 5,000–8,000 patients, with nearly 55%–65% of patients having a relapsing-remitting MS subtype of the disease. The aim of this review is to provide an overview of current and emerging treatments available in Argentina for patients with MS.

Epidemiology and clinical record of multiple sclerosis in selected countries: a systematic review

Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease of the central nervous system mainly affecting young adults. The aim of this paper is to review the literature concentrating the main national MS registries in selected countries of the world. We performed a systematic review to determine the MS epidemiology reported on prevalence, incidence, environmental factors, treatment, social consequences of MS and neurological disability or progression among MS-affected people. We got the information on the high-MS prevalence in Sardinia, Sweden or Sicily and on the effects of MS treatment in United States of America, Italy or Germany. We emphasized environmental factors taking into account as MS risk factors. We concluded that there were many descriptions of MS status in particular countries, but they were often insufficiently detailed and not uniform enough to compare it. The paper indicated an importance of the MS epidemiology in the light of the healthcare or quality of life of the MS patients, but further research is needed to optimize this issue.

Incidence and prevalence of multiple sclerosis in the Americas: a systematic review

BACKGROUND

The incidence and prevalence of multiple sclerosis (MS) varies considerably around the world. No previous study has performed a comprehensive review examining the incidence and prevalence of MS across the Americas. The purpose of this study was to systematically review and assess the quality of studies estimating the incidence and/or prevalence of MS in North, Central and South American regions.

METHODS

A comprehensive literature search was performed using MEDLINE and EMBASE from January 1985 to January 2011. Search terms included 'multiple sclerosis', 'incidence', 'prevalence' and 'epidemiology'. Only full-text articles published in English or French were included. Study quality was assessed using an assessment tool based on recognized guidelines and designed specifically for this study.

RESULTS

A total of 3,925 studies were initially identified, with 31 meeting the inclusion criteria. The majority of studies examined North American regions (n = 25). Heterogeneity was high among all studies, even when stratified by country. Only half of the studies reported standardized rates, making comparisons difficult. Quality scores ranged from 3/8 to 8/8.

CONCLUSION

This review highlights the gaps that still exist in the epidemiological knowledge of MS in the Americas, and the inconsistencies in methodologies and quality among the published studies. There is a need for future studies of MS prevalence and incidence to include uniform case definitions, employ comparable methods of ascertainment, report standardized results, and be performed on a national level. Other factors such as sex distribution, ethnic make-up and population lifestyle habits should also be considered.

Epidemiology of neurologically disabling disorders

Neurological disorders place a considerable burden upon individuals, their families, and society. Some like stroke are common, while others like amyotrophic lateral sclerosis are much rarer. Some conditions such as multiple sclerosis are reported to vary by latitude, while others such as traumatic brain injury can vary considerably by locality. Depending upon the nature of the lesion, and factors such as time since onset, the consequences to the individual may also vary considerably, not just among different disorders, but within a given disorder. Consequently the patterns of disease incidence, its prevalence, and its consequences are complex and may vary not just because of the condition itself, but also because, for example, case ascertainment may vary from study to study. The cumulative annual incidence of disabling neurological disorders is likely to exceed 1000 per 100000, or 1% of the population. The incidence is characterized by significant variation, which is mediated by genetic, geographical, demographic, and environmental factors. While useful comparisons can be made through standardization techniques, planning for local services should be based upon local epidemiology, whenever available.

The epidemiology of multiple sclerosis in Latin America and the Caribbean: a systematic review

The incidence and prevalence of multiple sclerosis (MS) varies geographically as shown through extensive epidemiological studies performed mainly in developed countries. Nonetheless, scant data is available in Latin America and the Caribbean (LAC). The objective of this review is to assess epidemiological data of MS in LAC. We conducted a systematic review of published articles and gray literature from January 1995 to May 2011. Twenty-two studies met the inclusion criteria after full-text review. Incidence data were found in only three studies and ranged from 0.3 to 1.9 annual cases per 100,000 person-years. Prevalence was reported in 10 studies and ranged from 0.83 to 21.5 cases per 100,000 inhabitants. The most prevalent subtype of MS was the relapsing–remitting form (48% to 91% of the series). No data about mortality were found. This study showed low frequency for MS in LAC compared with North American and European countries. The role of environmental and genetic factors should be well studied, providing new insights about its etiology.

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.

Optimizing outcomes in multiple sclerosis: consensus guidelines for the diagnosis and treatment of multiple sclerosis in Latin America

OBJECTIVE

The prevalence of multiple sclerosis (MS) in Latin America varies across different studies but an intermediate risk and increased frequency of the disease have been reported in recent years. The circumstances of Latin American countries are different from those of Europe and North America, both in terms of differential diagnoses and disease management.

METHODS

An online survey on MS was sent to 855 neurologists in nine Latin American countries. A panel of nine experts in MS analyzed the results.

RESULTS

Diagnostic and therapeutic recommendations were outlined with special emphasis on the specific needs and circumstances of Latin America. The experts proposed guidelines for MS diagnosis, treatment, and follow up, highlighting the importance of considering endemic infectious diseases in the differential diagnoses of MS, the identification of patients at high risk of developing MS in order to maximize therapeutic opportunities, early treatment initiation, and cost-effective control of treatment efficacy, as well as global assessment of disability.

CONCLUSIONS

The experts recommended that healthcare systems allocate a longer consultation time for patients with MS, which must be conducted by neurologists trained in the management of the disease. All drugs currently approved must be available in all Latin American countries and must be covered by healthcare plans. The expert panel supported the creation of a permanent forum to discuss future clinical and therapeutic recommendations that may be useful in Latin American countries.

Incidence of multiple sclerosis in Chile. A hospital registry study

OBJECTIVE

To study the incidence of MS in Chile by examining the hospitalizations across all geographical regions of the country and to examine whether there is a correlation between these rates and the latitude or ultraviolet radiation.

METHODS

This is a descriptive study examining the national registry of hospitalizations because of MS (code G35 in ICD-10) from January 1, 2001, to December 31, 2006. Incidence rates were calculated by gender and geographical region and standardized to the world population estimated for 2010.

RESULTS

A total of 6857 hospitalizations were analyzed. There were 935 individuals; 63.9% were women. The mean incidence rate for 2002-2006 period was 0,90 (95% CI: 0.75-1.05). The annualized incidence rates for regions from North to South were as follows: I Tarapaca 0.54 (95% CI: 0.0-1.21), II Antofagasta 0,93 (0.10-1.75), III Atacama 1.07 (0.0-2.31), IV Coquimbo 0.63 (0.01-1.24), V Valparaiso 0.83 (0.38-1.27), VI O'Higgins 0.72 (0.14-1.30), VII Maule 0.52 (0.06-0.98), VIII BIO BIO 0.81 (0.41-1.21), IX Araucanía 0.43 (0.0-0.86), X Los Lagos 0.91 (0.35-1.46), XI Aysen 0.99 (0.0-2.98), XII Magallanes 3.54 (0.57-6.51), and XIII Metropolitana 1.10 (0.84-1.36). There were no significant correlations between hospitalization rates and latitude, except for region XII. UV radiation levels showed significant differences only for region XII.

CONCLUSION

There is a moderate risk of MS in Chile. The southernmost region showed significantly higher incidence rates than those in the rest of the country (a cluster zone). We did not find any correlation between incidence rates and latitude or UV radiation.

Multiple sclerosis in Caucasians and Latino Americans

Epidemiological and genetic studies suggest that the prevalence, median age of onset, and specific phenotypes of multiple sclerosis (MS) are different in Caucasians and Latino Americans. Recent epidemiological studies indicate an increase in MS prevalence in Latin America (LA), where the south-north gradient of latitude described for Nordic countries does not exist. Analysis of MS epidemiological and specific aspects in LA suggests that susceptibility and clinical behavior of the disease are related to mixtures and admixtures of genes in the population. MS is not present in Amerindians with Mongoloid genes, such as occurs in other pure ethnic groups. Surely, future studies will be carried out to obtain more reliable information. In this review, we contrast and analyze the available data of MS in LA and endemic countries.

Latitudinal prevalence gradient of multiple sclerosis in Latin America

BACKGROUND

Multiple sclerosis (MS) has a unique geographical distribution that reflects both genetic and environmental factors. Many studies have shown a positive correlation between MS frequency and latitude across both large and small geographical regions. However, scarce data have been published on the epidemiology of MS in Latin America and no study has evaluated latitudinal variation.

OBJECTIVE

To evaluate the effect of latitude on MS prevalence in Latin America.

METHODS

We conducted a systematic review of MS prevalence during January 2011. Prevalence rates were collected from eligible publications. The effect of latitude on prevalence was analyzed using linear regression.

RESULTS

A total of ten studies were eligible for analysis, corresponding to six countries, spanning from Panama to Argentina. The crude prevalence of MS ranged from 0.75 to 21.5 per 100,000. We found a strong and significant association between prevalence and latitude (r(2) 0.8; p < 0.001) and determined an increase in prevalence of 0.33 per 100,000 per degree latitude.

CONCLUSION

Our findings suggest a latitudinal prevalence gradient of MS in Latin American countries between Panama and Argentina.

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.

MS prevalence in New Zealand, an ethnically and latitudinally diverse country

Background: The prevalence of multiple sclerosis (MS) is not uniform, with a latitudinal gradient of prevalence present in most studies. Understanding the drivers of this gradient may allow a better understanding of the environmental factors involved in MS pathogenesis.

Method: The New Zealand national MS prevalence study (NZMSPS) is a cross-sectional study of people with definite MS (DMS) (McDonald criteria 2005) resident in New Zealand on census night, 7 March 2006, utilizing multiple sources of notification. Capture—recapture analysis (CRA) was used to estimate missing cases.

Results: Of 2917 people with DMS identified, the crude prevalence was 72.4 per 100,000 population, and 73.1 per 100,000 when age-standardized to the European population. CRA estimated that 96.7% of cases were identified. A latitudinal gradient was seen with MS prevalence increasing three-fold from the North (35°S) to the South (48°S). The gradient was non-uniform; females with relapsing—remitting/secondary-progressive (RRMS/SPMS) disease have a gradient 11 times greater than males with primary-progressive MS ( p < 1 × 10-7). DMS was significantly less common among those of Māori ethnicity.

Conclusions: This study confirms the presence of a robust latitudinal gradient of MS prevalence in New Zealand. This gradient is largely driven by European females with the RRMS/SPMS phenotype. These results indicate that the environmental factors that underlie the latitudinal gradient act differentially by gender, ethnicity and MS phenotype. A better understanding of these factors may allow more targeted MS therapies aimed at modifiable environmental triggers at the population level.

Is hypovitaminosis D one of the environmental risk factors for multiple sclerosis?

The role of hypovitaminosis D as a possible risk factor for multiple sclerosis is reviewed. First, it is emphasized that hypovitaminosis D could be only one of the risk factors for multiple sclerosis and that numerous other environmental and genetic risk factors appear to interact and combine to trigger the disease. Secondly, the classical physiological notions about vitamin D have recently been challenged and the main new findings are summarized. This vitamin could have an important immunological role involving a number of organs and pathologies, including autoimmune diseases and multiple sclerosis. Furthermore, human requirements for this vitamin are much higher than previously thought, and in medium- or high-latitude countries, they might not be met in the majority of the general population due to a lack of sunshine and an increasingly urbanized lifestyle. Thereafter, the different types of studies that have helped to implicate hypovitaminosis D as a risk factor for multiple sclerosis are reviewed. In experimental autoimmune encephalomyelitis, vitamin D has been shown to play a significant immunological role. Diverse epidemiological studies suggest that a direct chain of causality exists in the general population between latitude, exposure to the sun, vitamin D status and the risk of multiple sclerosis. New epidemiological analyses from France support the existence of this chain of links. Recently reported immunological findings in patients with multiple sclerosis have consistently shown that vitamin D significantly influences regulatory T lymphocyte cells, whose role is well known in the pathogenesis of the disease. Lastly, in a number of studies on serum levels of vitamin D in multiple sclerosis, an insufficiency was observed in the great majority of patients, including at the earliest stages of the disease. The questionable specificity and significance of such results is detailed here. Based on a final global analysis of the cumulative significance of these different types of findings, it would appear likely that hypovitaminosis D is one of the risk factors for multiple sclerosis.

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.

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.

A systematic review of the epidemiology of multiple sclerosis in South America

Hundreds of publications dealing with the prevalence of multiple sclerosis (MS) throughout the world exist, but little data have been published from South America. Epidemiological studies of MS vary according to environmental, racial and genetic factors; a better understanding of MS in South America would help us to elucidate the disease pattern in this population. The aim of this study is to review the evidence relevant to MS epidemiology in South America. We performed a systematic review of articles of MS epidemiology in South America, with special emphasis on those providing information on the incidence and prevalence of MS (population-based studies). Six papers provided information on MS epidemiology. One paper used the capture-recapture methodology, while the remainder employed traditional methods to collect the data. Population-based studies showed an MS prevalence rate ranging from 1.48 to 17 per 100 000 inhabitants. Available data suggest that the prevalence of MS is lower in South America than in developed countries. The reason for this observation is unknown. Some investigators suggest that certain environmental factors like sun exposure and vitamin D supplementation or the called 'hygiene hypothesis' may protect this population. Future studies will contribute to elucidate the etiology of that difference.

Prevalence of multiple sclerosis in Buenos Aires, Argentina using the capture-recapture method

BACKGROUND

Scarce data exist about multiple sclerosis (MS) prevalence in South America. The objective of the study is to determine the prevalence of MS in a high populated area from Argentina (Greater Buenos Aires Metropolitan area) using the capture-recapture methodology.

METHODS

Greater Buenos Aires is the generic denomination that refers to the megalopolis comprised by the autonomous city of Buenos Aires and the surrounding conurbation of the province of Buenos Aires. The study was carried out taking July 1996 as the prevalence month. We used capture-recapture method to estimate the prevalence of MS cross matching registries from four MS Centers.

RESULTS

A total of 803 registries were obtained from the four lists. Log-linear model for capture-recapture method was used to analyze the data. The population of the area based on the 1990 census was 12,594,974; the number of MS cases estimated amongst sources interactions were between 1833 and 2359; the prevalence estimated ranged from 14 to 19.8 cases per 100,000 inhabitants.

CONCLUSIONS

This is the first study to provide epidemiological data on the prevalence of MS in a large population in Argentina (Greater Buenos Aires Metropolitan area). Further epidemiological studies will clarify the true prevalence of MS in South America.