Incidence and Prevalence of Multiple Sclerosis in Newfoundland and Labrador

Systematic literature review and meta-analysis of the prevalence of secondary progressive multiple sclerosis in the USA, Europe, Canada, Australia, and Brazil

Background

Secondary progressive multiple sclerosis (SPMS) is a subtype of multiple sclerosis (MS), which is a chronic neurological disease, characterised by inflammation of the central nervous system. Most of MS patients eventually progress to SPMS. This study estimates the prevalence of SPMS in the United States of America, Europe, Canada, Australia, and Brazil.

Methods

A systematic literature search of the Medline and Embase databases was performed using the OVID™ SP platform to identify MS epidemiological studies published in English from database inception to September 22, 2020. Studies reporting the prevalence of MS and proportion of SPMS patients in the included population were selected. The pooled prevalence of SPMS was calculated based on the proportion of SPMS patients. The Loney quality assessment checklist was used for quality grading. A meta-analysis of the proportions was conducted in RStudio.

Results

A total of 4754 articles were retrieved, and prevalence was calculated from 97 relevant studies. Overall, 86 medium- and high-quality studies were included in the meta-analysis. Most studies were conducted in European countries (84 studies). The estimated pooled prevalence of SPMS was 22.42 (99% confidence interval: 18.30, 26.95)/100,000. The prevalence of SPMS was more in the North European countries, highest in Sweden and lowest in Brazil. A decline in SPMS prevalence was observed since the availability of oral disease-modifying therapies. We also observed a regional variation of higher SPMS prevalence in urban areas compared with rural areas.

Conclusion

High variability was observed in the estimated SPMS prevalence, and the quality of the studies conducted. The influence of latitude and other factors known to affect overall MS prevalence did not fully explain the wide range of inter-country and intra-country variability identified in the results.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-022-02820-0.

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.

High incidence and increasing prevalence of multiple sclerosis in British Columbia, Canada: findings from over two decades (1991-2010)

Province-wide population-based administrative health data from British Columbia (BC), Canada (population: approximately 4.5 million) were used to estimate the incidence and prevalence of multiple sclerosis (MS) and examine potential trends over time. All BC residents meeting validated health administrative case definitions for MS were identified using hospital, physician, death, and health registration files. Estimates of annual prevalence (1991–2008), and incidence (1996–2008; allowing a 5-year disease-free run-in period) were age and sex standardized to the 2001 Canadian population. Changes over time in incidence, prevalence and sex ratios were examined using Poisson and log-binomial regression. The incidence rate was stable [average: 7.8/100,000 (95 % CI 7.6, 8.1)], while the female: male ratio decreased (p = 0.045) but remained at or above 2 for all years (average 2.8:1). From 1991–2008, MS prevalence increased by 4.7 % on average per year (p < 0.001) from 78.8/100,000 (95 % CI 75.7, 82.0) to 179.9/100,000 (95 % CI 176.0, 183.8), the sex prevalence ratio increased from 2.27 to 2.78 (p < 0.001) and the peak prevalence age range increased from 45–49 to 55–59 years. MS incidence and prevalence in BC are among the highest in the world. Neither the incidence nor the incidence sex ratio increased over time. However, the prevalence and prevalence sex ratio increased significantly during the 18-year period, which may be explained by the increased peak prevalence age of MS, longer survival with MS and the greater life expectancy of women compared to men.

The effects of exergaming on balance, gait, technology acceptance and flow experience in people with multiple sclerosis: a randomized controlled trial

Background

Exergaming is a promising new alternative to traditional modes of therapeutic exercise which may be preferable and more effective for people with Multiple Sclerosis (MS). Impaired balance is reported as one of the most disabling aspects of MS. The purposes of this study were to examine the effects of exergaming on: (1) postural sway, (2) gait, (3) technology acceptance and (4) flow experience in people with MS. Secondary outcomes were disability: 12‐item Multiple Sclerosis Walking Scale (MSWS-12) and the World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0) questionnaire.

Methods

Fifty-six adults (mean age = 52 years, SD = 5.8; 38 women) with a clinical diagnosis of MS and able to walk 100 meters with or without use of a walking aid were included in this study and randomized into 3 groups. Group 1 received balance training using the Nintendo Wii Fit™ (exergaming) and Group 2 undertook traditional balance training (non-exergaming). Group 3 acted as a control group, receiving no intervention. Exergaming and traditional balance training groups received four weeks of twice weekly balance-orientated exercise. Postural sway was measured using a Kistler™ force platform. Spatiotemporal parameters of gait were measured using a GAITRite™ computerised walkway. Technology acceptance and flow experience were measured using the Unified Theory of Acceptance and Use of Technology and the Flow State Scale questionnaires, respectively.

Results

There were significant improvements in bipedal postural sway in both intervention groups when compared to the control group; and no effects of either intervention on gait. There were no significant differences between the interventions in technology acceptance but on several dimensions of flow experience the Wii Fit™ was superior to traditional balance training. Both interventions showed improvements in disability compared to control.

Conclusions

In terms of the physical effects of exergaming, the Wii Fit™ is comparable to traditional balance training. These findings would support the use of the Wii Fit™ as an effective means of balance and gait training for people with MS, which is both accepted and intrinsically motivating to MS users.

Trial registration

Controlled Trials ISRCTN13924231.

Prevalence of Multiple Sclerosis in Canada: A Systematic Review

Background:

Studies of the prevalence of multiple sclerosis (MS) in Canada have generally been isolated to specific regions. Given the importance of multiple sclerosis as a cause of disability in adults, a comprehensive review of Canadian MS prevalence examining current data, interregional variation, deficiencies in knowledge and frontiers for research is timely.

Methods:

A systematic review of all studies addressing the prevalence of MS in Canada or regions within Canada, published in English or French since 1985, was conducted. Studies were identified using MEDLINE, EMBASE and bibliographic review. Ten studies were evaluated for methodological rigour and a test of heterogeneity across studies was performed and a measure of consistency (I2) estimated.

Results:

Studies were generally of high quality. Nine were restricted to regions within Canada and one provided an estimated national prevalence based on self-reported cases. All reported a high prevalence (>50 per 100 000). Latitude and longitude gradients were not striking while assessment of heterogeneity confirmed that regional differences were unlikely to be the result of sampling variability.

Conclusions:

This review confirms Canada as a country of very high MS prevalence and it is the first study to demonstrate that variation in regional estimates represents true differences in prevalence within Canada. Avenues for future MS prevalence research, including adoption of a national MS registry, are proposed.

The Liberation Procedure Decision-Making Experience for People With Multiple Sclerosis

Despite the absence of scientific evidence demonstrating the efficacy of the "liberation procedure" in treating multiple sclerosis (MS), thousands of MS patients worldwide have undergone the procedure. The study objective was to explore the experience of liberation procedure decision making for individuals with MS. Fifteen adults in Newfoundland and Labrador, Canada, each participated in an in-depth interview. The data analysis revealed three groups of people: "waiters," "early embracers," and "late embracers." Using van Manen's hermeneutic phenomenological approach, we identified three themes each in the stories of the early and late embracers and four themes in the waiters' stories. A characteristic of the late embracers and waiters was skepticism, whereas desperation set the embracers apart from the waiters. With a deeper understanding of the experience, nurses can be more attuned to the perspectives of MS patients while helping them make informed decisions about undergoing the liberation procedure.

The Incidence and Prevalence of Multiple Sclerosis in Nova Scotia, Canada

Background:

Estimates of incidence and prevalence are needed to determine disease risk and to plan for health service needs. Although the province of Nova Scotia, Canada is located in a region considered to have a high prevalence of multiple sclerosis (MS), epidemiologic data are limited.

Objective:

We aimed to validate an administrative case definition for MS and to use this to estimate the incidence and prevalence of MS in Nova Scotia.

Methods:

We used provincial administrative claims data to identify persons with MS. We validated administrative case definitions using the clinical database of the province's only MS Clinic; agreement between data sources was expressed using a kappa statistic. We then applied these definitions to estimate the incidence and prevalence of MS from 1990 to 2010.

Results:

We selected the case definition using ≥7 hospital or physician claims when >3 years of data were available, and ≥3 claims where less data were available. Agreement between data sources was moderate (kappa = 0.56), while the positive predictive value was high (89%). In 2010, the age-standardized prevalence of MS per 100,000 population was 266.9 (95% CI: 257.1- 277.1) and incidence was 5.17 (95% CI: 3.78-6.56) per 100,000 persons/year. From 1990-2010 the prevalence of MS rose steadily but incidence remained stable.

Conclusions:

Administrative data provide a valid and readily available means of estimating MS incidence and prevalence. MS prevalence in Nova Scotia is among the highest in the world, similar to recent prevalence estimates elsewhere in Canada.

BG-12 (dimethyl fumarate): a review of mechanism of action, efficacy, and safety

BACKGROUND

Multiple sclerosis (MS) is a chronic inflammatory disease, affecting more than 2.5 million people worldwide with more 400,000 cases in the United States alone. There has been considerable improvement in the treatment of MS, with the introduction of disease-modifying drugs; however, new oral therapies may provide additional benefit by providing an alternative treatment modality and the potential for improved adherence by avoiding the injection-associated side effects and anxiety encountered with some first-line agents. BG-12 (dimethyl fumarate) is an oral agent approved in the United States for the treatment of relapsing forms of MS.

SCOPE

We review published literature about what is known about the mechanism of action of BG-12, and key efficacy and safety findings from three clinical studies in patients with relapsing-remitting MS (RRMS).

FINDINGS

Data from preclinical studies have demonstrated that BG-12 may promote anti-inflammatory and cytoprotective activities that are mediated, at least in part, by the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) antioxidant response pathway. Studies in animals have shown a protective effect of BG-12 on neuronal, axonal and myelin integrity. Results from a phase 2 study and two randomized double-blind placebo-controlled phase 3 studies, CONFIRM and DEFINE, have shown that BG-12 provides clinical and radiologic efficacy in patients with RRMS. At 2 years, BG-12 240 mg twice and three times daily reduced annualized relapse rate (CONFIRM primary endpoint) by 44% and 51% and the risk of relapse (DEFINE primary endpoint) by 49% and 50%, respectively, compared with placebo (all p < 0.001). BG-12 was generally well tolerated and had an acceptable safety profile, with a similar incidence of adverse events across treatment groups.

CONCLUSIONS

BG-12 may have cytoprotective and anti-inflammatory properties that contribute to its efficacy among patients with RRMS. Findings from phase 2 and 3 studies further support BG-12 as an effective initial therapy. ClinicalTrials.gov ID: NCT00168701; NCT00420212: NCT00451451.

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.

Development of oral immunomodulatory agents in the management of multiple sclerosis

The emergence of oral disease-modifying therapies in multiple sclerosis (MS) will have a significant impact on the evolving scenario of immunomodulatory treatments in MS where current therapies are all injectable. Reducing relapses in trials translates for individuals with MS into a therapeutic aim of stopping future events. Thus the possible absence of any perceived benefits to the individual together with the long disease course, variable outcome, and a younger age group affected in MS makes side effects the major issue. The use of disease-modifying therapies as a whole needs to be placed in the context of a widening therapeutic indication where the use of these therapies is being justified at an increasingly early stage and in pre-MS syndromes such as clinically isolated and radiologically isolated syndromes where no fixed disability is likely to have accumulated. The five oral therapies discussed (cladribine, fingolimod, laquinimod, BG-12, and teriflunomide) have just completed Phase III studies and some have just been licensed. New oral drugs for MS need to be placed within this evolving marketplace where ease of delivery together with efficacy and side effects needs to be balanced against the known issues but also the known long-term safety of standard injectables.

Prevalence of multiple sclerosis in Dubai, United Arab Emirates

BACKGROUND

The prevalence of multiple sclerosis (MS) is rapidly changing.

OBJECTIVES

To determine the prevalence and incidence of MS in Dubai, UAE.

METHODS

Data for all MS patients fulfilling McDonald criteria and registered in the Neurology Department, Rashid Hospital, Dubai between January 01, 2000 to December 12, 2007 were analyzed.

RESULTS

Two hundred and eighty-four MS patients were identified of which 158 (55.6%) were Dubai Natives and 126 (44.4%) Immigrants. In the Dubai Native population, the female to male ratio was 2.85:1. Motor manifestation was the commonest presentation 72.78% followed by sensory symptom 48.41%. The median and mean expanded disability status scale (EDSS) was 1.5 and 2.38 respectively. The mean age of onset was 26.66 ± 6.6 years. The prevalence of MS in 2007 was 54.77/100,000 (95% C.I. 46.99-62.55) with an annual incidence rate of 6.8/100,000 (95% C.I. 3.8-9.87) during 2000-2007.

CONCLUSION

Dubai should be considered as one of the regions with medium to high risk for MS, with prevalence rate higher than what has been previously believed. This high MS incidence and prevalence in Dubai is surprising and it may represent a true increase. Central MS registry and long-term follow-up epidemiological studies are recommended.

Understanding and meeting injection device needs in multiple sclerosis: a survey of patient attitudes and practices

BACKGROUND

All established disease-modifying drugs for multiple sclerosis require parenteral administration, which can cause difficulties for some patients, sometimes leading to suboptimal adherence. A new electronic autoinjection device has been designed to address these issues.

METHODS

Patients with relapsing multiple sclerosis currently receiving subcutaneous or intramuscular interferon beta-1a, interferon beta-1b, or glatiramer acetate completed an online questionnaire (July 4-25, 2008) that surveyed current injection practices, experiences with current injection methods, and impressions and appeal of the new device.

RESULTS

In total, 422 patients completed the survey, of whom 44% used autoinjectors, 43% prefilled syringes, and 13% syringes and vials; overall, 66% currently self-injected. Physical and psychological barriers to self-injection included difficulty with injections, needle phobia, and concerns over correct injection technique. Only 40% of respondents were "very satisfied" with their current injection method. The new electronic autoinjector was rated as "very appealing" by 65% of patients. The benefits of the new device included the ability to customize injection settings and to review dosing history.

CONCLUSION

New technologies may help patients overcome physical and psychological barriers to self-injection. The combination of a reliable and flexible autoinjection device with dose-monitoring technology may improve communication between health care professionals and patients, and improve treatment adherence.

Gender issues in multiple sclerosis: an update

Although multiple sclerosis (MS) affects both women and men, women are more susceptible to MS than men. Accumulating evidence indicates that the incidence and prevalence of MS is increasing, more so in women than in men. Owing to pregnancy, differing hormonal states and distinct social roles, the impact of MS differs between women and men. Since Patricia K Coyle published a review on gender issues in MS, multiple studies have added to the body of knowledge. This update will summarize the current thinking on gender-related issues in MS and we will address incidence and prevalence, hormonal factors, pregnancy and breastfeeding, genetics, course and prognosis, imaging, treatment and psychosocial aspects. Future progression within this field will help elucidate the cause of and define the treatment of 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.

The prevalence of multiple sclerosis in central Italy

Background: The prevalence of multiple sclerosis varies considerably throughout the world.

Objective: To better define the prevalence of MS in central Italy.

Methods: This is a population-based study conducted in the province of Frosinone, which is situated in the Lazio region, central Italy. The selected prevalence day was 1 January 2007. A total of 467 patients, with a definite diagnosis of multiple sclerosis, were considered for crude, age- and sex-specific prevalence estimation.

Results: The overall crude prevalence rate was 95.0 cases per 100,000 (95% confidence interval (CI) 86.6—104.0). A significantly higher prevalence rate was recorded in females (134.9, 95% CI 121.0—150.1) than in males (53.3, 95% CI 44.4—63.3) ( p = 0.001). Age-specific prevalence peaked in the 25—34 year, 35—44 year and 45—54 year age groups; moreover, it was found to increase up to the 35—44 year age group in males and the 45—54 year age group in females, decreasing thereafter. The female to male ratio was 2.6.

Conclusions: The results confirm that MS occurs more frequently in central Italy than might be expected on the basis of the geographic-related distribution model, thus supporting the view that this is a high-risk area for the disease.

Factors associated with delay to medical recognition in two Canadian multiple sclerosis cohorts

Long referral and diagnostic delays can impact both the opportunity for early therapeutic intervention and estimates of MS incidence and prevalence. We investigated factors associated with diagnostic or referral delays within two geographically distinct MS Canadian cohorts and the association between referral delay and disability at first clinic visit. Adult-onset MS patients were selected from the population-based British Columbian MS (BCMS) (n=5705) and the clinic-based Hôpital Notre-Dame, Quebec (CHUM) (n=1489) databases. Referral delay (BCMS) and diagnostic delay (CHUM) were examined by sex, onset age, disease course (primary progressive (PPMS) vs. relapsing at onset), onset symptoms (BCMS only) and year of first clinic visit/diagnosis. Cohorts were analyzed separately by stratified analyses and multivariable linear modeling. The relationship between referral delay and initial disability was examined by multiple ordinal regression in the BCMS cohort. Younger at onset patients or those with PPMS exhibited significantly longer delays (p<0.001). Delays decreased over the 20+ year period, but reductions varied by clinical course, onset age and sex. Long referral delays were associated with greater disability at first clinic visit (p<0.001). If early intervention at mild disability levels is warranted in MS, then the extended delays to medical recognition for young adult-onset and PPMS patients must be addressed.

Explaining multiple sclerosis prevalence by ultraviolet exposure: a geospatial analysis

BACKGROUND

Epidemiologic studies have shown a positive correlation of multiple sclerosis (MS) prevalence with latitude. However, there has not been a causal association found. Increased dietary intake and increased serum levels of vitamin D showed to be protective for the development of MS. Ultraviolet (UV) radiation plays an important role in vitamin D synthesis and could potentially explain both latitude differences in MS prevalence and the low levels of vitamin D in individuals with MS.

OBJECTIVE

To evaluate the relationship between UV radiation and MS prevalence using geospatial analysis.

METHODS

Geospatial analysis was performed on North American regions and separately for the continental United States. The correlation of UV radiation (measured as UV index [UVI]) versus MS prevalence and UV radiation versus case-control ratios was calculated. In addition, the relative risk (RR) of MS was determined for regions/states with low UV radiation exposure.

RESULTS

Case-control ratios by US state and MS prevalence by North American region showed a strong negative (inverse) correlation with UVI (R = -0.72 and -0.86, respectively). The RR for the five highest risk states/lowest UVI versus the five lowest risk states/highest UVI was increased (RR = 1.8-5.4). The RR for MS, when comparing North American regions with lowest and highest UVI, was 3.78 and within US regions was 1.52.

CONCLUSION

This analysis suggests a strong association between UV radiation and MS distribution, and an increase in risk for MS in those areas with a low UVI.

Contribution of incidence to increasing prevalence of multiple sclerosis in Alberta, Canada

Alberta Health Care Insurance Plan (AHCIP) data were used to calculate prevalence and incidence rates for multiple sclerosis (MS) in the general population of Alberta from 1990 to 2004. Multiple sclerosis prevalence rose steadily each year over this time period, from 217.6/100,000 individuals in 1990 to 357.6/100,000 in 2004. Multiple sclerosis incidence fluctuated with a slight increase from 1990 to 2004, at 20.9/100,000 and 23.9/100,000, respectively. Age-specific prevalence rates were higher between ages 30 and 60 in 2004 than in 1990. The pattern of age-specific incidence rates was similar in 1990 and 2004, with a slight shift toward diagnosis in younger years. Gender-specific prevalence rates were higher for females in both 1990 and 2004, with a greater increase in females (43%) than males (29%). Gender-specific incidence rates were higher for females than males in both years, but there was no differential increase in incidence by gender from 1990 to 2004. The 2004 Alberta MS prevalence rate remains among the highest reported worldwide. Both increasing incidence and longer duration have likely contributed to increasing MS prevalence in the province.

The relation of ultraviolet radiation and multiple sclerosis in Newfoundland

BACKGROUND

It has been thought that the occurrence of multiple sclerosis (MS) could be associated with daily ultraviolet exposure. In this study we investigated the geospatial association between average daily ultraviolet B (UVB) irradiance and MS prevalence in Newfoundland and Labrador (NL), Canada.

METHODS

A complete list of patients diagnosed with MS in the province of NL was constructed. Places of habitation from birth to diagnosis were ascertained by mailout survey.

RESULTS

A 74% rate of return on the survey results was obtained. A plot of the average daily erythemal UV over the available five years (1998-2002) shows that the distribution of MS follow a north-south gradient. Average daily UVB measurements are lower in the higher latitudes. A statistically significant negative correlation of MS incidence with erythemal UVB was found that is stronger than the correlation using latitude. This correlation appears to be strongest in the first year of life and declines when subsequent years are examined up to age ten. No significant correlation was found for the subjects' locale of habitation at the time of their first MS attack.

CONCLUSIONS

This study suggests that UVB radiation may contribute to the pathogenesis of MS.

Multiple sclerosis in the province of Ferrara : evidence for an increasing trend

BACKGROUND

Epidemiological studies on the distribution of multiple sclerosis (MS) conducted in the Mediterranean area in the last two decades have disclosed a significant increase in frequency of the disease, indicating caution when a latitude-related model of MS is accepted. Previous descriptive surveys in the province of Ferrara, northern Italy, carried out by our own epidemiological research group, have established that this area is at high risk for MS.

OBJECTIVE

To confirm the above assumption and to update MS frequency estimates in this area.

DESIGN AND SETTING

We conducted a community-based intensive prevalence and incidence study, by adopting a complete enumeration approach.

RESULTS

On December 31, 2004, 423 patients (300 women and 123 men) suffering from definite or probable MS (Poser's criteria) living in the province of Ferrara, yielded a crude prevalence rate of 120.93 (95 % CI, 110.05-134.23) per 100,000, 164.26 for women and 73.59 for men. The average incidence from 1990 to 2003 was 4.35 per 100,000 (95 % CI, 3.77-4.99), 5.91 for women and 2.63 for men. The incidence rate,which was relatively stable during the previous 25 years (1965-1989) with a mean rate of 2.3 per 100,000, increased to a value of 3.39 per 100,000 in the period 1990-1994, 4.09 per 100,000 in the period 1995-1999 and 3.84 per 100,000 in the period 2000-2003.

CONCLUSIONS

These results confirm that in Ferrara MS occurs more frequently than suggested by the geographic- related distribution model and, based on other recent national surveys, support the view that northern Italy is a high-risk area for the disease. The marked increase in MS prevalence rate, in comparison with previous investigations, is in part due to the increasing survival of patients as a result of improved supportive care and the accumulation of new incidence cases owing to the reduction in diagnostic latency for better quality of neurological diagnostic procedures. The incidence in the province of Ferrara was found to slowly change with an incremental trend,which cannot only be attributed to improvements in diagnostic ability. Environmental risk factors in genetically predisposed people over time could be considered.

Prevalence of multiple sclerosis in First Nations people of Alberta

BACKGROUND

Multiple Sclerosis (MS) is reported to be uncommon among North American aboriginals despite frequent intermarriage with people of European ancestry, but few population-based studies have been conducted. The purpose of this study was to determine the prevalence of MS among First Nations aboriginal people in Alberta, Canada compared to the general population.

METHODS

All hospital in-patient and physician fee-for-service records between 1994 and 2002 where a diagnosis of MS was mentioned were extracted from government health databases in the province of Alberta. First Nations people can be identified since the federal government (Health Canada) pays health care insurance premiums on their behalf. Multiple Sclerosis prevalence per 100,000 population for both First Nations people and the general population of Alberta were calculated for each year during this time span.

RESULTS

Among First Nations in Alberta, MS prevalence was 56.3 per 100,000 in 1994 and 99.9 per 100,000 in 2002, an increase of 43.6%. In 2002 prevalence was 158.1 and 38.0 for females and males respectively, a female to male ratio of 4.2:1. Multiple Sclerosis prevalence among the general population of Alberta was 262.6 per 100,000 in 1994 and 335.0 per 100,000 in 2002, an increase of 21.6%. In 2002 prevalence was 481.5 and 187.5 for females and males respectively, a female to male ratio of 2.6:1. Peak prevalence for both First Nations and general population females in 2002 was age 50-59, also 50-59 for both First Nations and general population males.

CONCLUSION

While MS prevalence in First Nations people is lower than in the general population of Alberta, it is not rare by worldwide standards.

Increasing incidence of multiple sclerosis among women in Lorraine, Eastern France

This study aims to describe the prevalence and incidence rates of multiple sclerosis (MS) in Lorraine, France, and its secular trend from 1990 to 2002. Cases were sourced from the regional network of MS healthcare workers in the Lorraine region and include all cases with definite or probable MS according to Poser's criteria. We identified 2718 patients with MS on 31 December 2004. The prevalence rate was 120/100,000 (95% confidence interval [CI]: 119-121). Between 1990 and 2002, the average age- and sex-adjusted annual incidence rate was 5.5/100,000 (95% CI: 4.4-6.6). During this same period, there was a significant increase in overall incidence in women but not in men. The mean age at MS onset, disability score five years after onset, number of relapses during the first five years, and proportion of first attack with sequelae or polysymptomatic symptoms were not significantly different between each annual cohort during the study period. The prevalence and incidence rates of MS we found in our study were higher than in previous studies in France. The increase in incidence of MS between 1990 and 2002, mostly in women, was not related to better ascertainment of patients with mild disability.

Multiple Sclerosis in Isfahan, Iran

BACKGROUND

This survey was planned to study the prevalence and incidence of multiple sclerosis (MS) in Isfahan, Iran and to describe the clinical features of MS in general and in specific subgroups of patients (early-onset, late-onset, familial, and conjugal cases) and to compare our results with other reports.

METHODS

A cross-sectional study was conducted from April 5, 2003 to July 31, 2006. All patients known to have definite MS according to McDonald's criteria, alive, resident within Isfahan (a large province of Iran) and members of Isfahan MS Society (IMSS) were included in the study. Demographic and case-related information were recorded. A total number of 1718 definite MS patients (388 men and 1330 women) were identified from IMSS database.

RESULTS

The overall period prevalence of MS was 43.8/100,000. Among men the prevalence was 19.2 (95% CI: 17.4-21.2)/100,000 and among women 69.6 (95% CI: 66-73.4)/100,000. A female preponderance of 3.4 existed among these patients. In the year 2005, 143 new cases were diagnosed, resulting in an incidence rate of 3.64/100,000. The mean age of onset was 25.36 +/- 8.6 years (range 5-63 year), and mean duration of disease was 7.1 (+/-5.2) years for men and 6.7 (+/-5) years for women. Sensory and visual disturbances were the most common initial presentations with a prevalence of 51.7% and 47.5%, respectively. Cases identified include: early-onset MS (less than 15 years old at onset) with 87 cases (5%), late-onset MS (over 50 years old at onset) with 20 cases (1.1%), familial MS with 209 cases (12.2%), and conjugal MS with 6 cases (0.5%).

CONCLUSION

Isfahan is a medium- to high-risk area for MS, with prevalence higher than what has previously been reported, possibly because of an increase in the incidence rate. Clinical and demographic characteristics were similar to other reports; however, some differences existed.

Sex ratio of multiple sclerosis in Canada: a longitudinal study

BACKGROUND

Incidence of multiple sclerosis is thought to be increasing, but this notion has been difficult to substantiate. In a longitudinal population-based dataset of patients with multiple sclerosis obtained over more than three decades, we did not show a difference in time to diagnosis by sex. We reasoned that if a sex-specific change in incidence was occurring, the female to male sex ratio would serve as a surrogate of incidence change.

METHODS

Since environmental risk factors seem to act early in life, we calculated sex ratios by birth year in 27 074 Canadian patients with multiple sclerosis identified as part of a longitudinal population-based dataset.

FINDINGS

The female to male sex ratio by year of birth has been increasing for at least 50 years and now exceeds 3.2:1 in Canada. Year of birth was a significant predictor for sex ratio (p<0.0001, chi(2)=124.4; rank correlation r=0.84).

INTERPRETATION

The substantial increase in the female to male sex ratio in Canada seems to result from a disproportional increase in incidence of multiple sclerosis in women. This rapid change must have environmental origins even if it is associated with a gene-environment interaction, and implies that a large proportion of multiple sclerosis cases may be preventable in situ. Although the reasons why incidence of the disease is increasing are unknown, there are major implications for health-care provision because lifetime costs of multiple sclerosis exceed pound1 million per case in the UK.

The relation between menarche and the age of first symptoms in a multiple sclerosis cohort

BACKGROUND

Previously, multiple sclerosis (MS) has been thought to be associated with changes in hormone levels. This study investigates the association between the age of menarche and the age of onset of the first symptoms of MS.

METHODS

A complete list of patients diagnosed with MS in the province of Newfoundland and Labrador was constructed. The age of menarche for our entire relapsing remitting female MS (RRMS) population was requested by mailout survey. Age of symptom onset was ascertained by chart review.

RESULTS

A 74% rate of return on the survey results was obtained (150 RRMS patients). A linear regression model demonstrated that the age of first symptoms increased by 1.16 years as the age of menarche increased by one year (R2 = 0.69, P = 0.04). Another analysis showed that the average age of first symptoms for women with reported menarche from 10 to 12 years was 28.96 years compared with 31.83 years for a reported menarche from 13 to 15 years, a significant difference (P = 0.047, t-test).

CONCLUSIONS

This study suggests that menarche may be related to the pathogenesis of MS.

Differential twin concordance for multiple sclerosis by latitude of birthplace

OBJECTIVE

To address the inconsistency in the reported concordance of multiple sclerosis (MS) among twins by zygosity, sex, and latitude.

METHODS

Four hundred eighteen medically documented monozygotic (MZ) and 380 same-sex dizygotic (DZ) pairs were ascertained from 1980 to 1992 and followed. The study population was representative of twins with multiple sclerosis. Twins from Canada and adjacent US states (at or above 41-42 degrees N) were considered "northern," and ancestry was dichotomized from descent from high-risk populations. Diagnosis before median age 29.3 years was considered "early."

RESULTS

The MZ/DZ concordance ratio was 2.9 (95% confidence interval [CI], 1.0-8.9) among men and 2.6 (95% CI, 1.5-4.5) among women. The average age at northern diagnosis was independent of ancestry and 2 years earlier for both MZ (p < 0.02) and DZ (p < 0.01) patients. Among DZ twins, concordance was independent of all characteristics. Among MZ twins, concordance was 1.9 times (95% CI, 1.2-3.2) greater among northern twins, 1.9 (95% CI, 1.1-3.6) times greater among twins with high-risk ancestry, and 2.1 (95% CI, 1.2-3.6) times greater if diagnosis was early. Ancestry and early diagnosis made independent significant contributions to the differential concordance by latitude.

INTERPRETATION

Multiple sclerosis is similarly heritable by sex, and the apparent variation in MZ concordance by latitude is influenced by environmental and genetic factors.

Prevalence of multiple sclerosis in Isfahan, Iran

BACKGROUND

The prevalence of multiple sclerosis (MS) shows considerable variability all over the world. According to Kurtzke, Iran is considered to have a low prevalence.

OBJECTIVE

To estimate the period prevalence and risk factors of MS in Isfahan, central part of Iran.

METHODS

A cross-sectional case register study conducted between 2004 and 2005. In the province of Isfahan, Iran, all patients known to have definite MS during 2004 and 2005, being alive and resident within Isfahan as well as being a member of the Isfahan MS Association were included in the study. Demographic and case-related information was recorded. 1,391 definite MS patients (308 men and 1,083 women) from the Isfahan MS Association, Iran, have been identified. The disease was confirmed using clinical information and MRI findings by a neurologist and radiologist. The patients were evaluated by interview and a questionnaire. Population data were obtained from the year 1999 Iran Census. The mean (SD) age of the participants was 32.5 (9.3) years with a mean (SD) duration of the disease of 6.4 (5.1) years for men and 6.9 (5.3) years for women.

RESULTS

The period prevalence of MS was 35.5 per 100,000 [95% confidence interval (CI) 33.6-37.3] in a population of 3,923,255, with a higher rate in women than men [54.5 (95% CI: 51.1-57.8) for women and 14.9 (95% CI: 13.3-16.6) for men]. The female/male ratio was 3.6 (95% CI: 3.2-4.1). The direct age-adjusted period prevalence was 59.5 per 100,000 (95% CI: 44.8-75.2) for women and 17.0 per 100,000 (95% CI: 8.9-25.1) for men. MS rates were highest among 30- to 39-year-olds and decreased with increasing age. Sensory and visual disturbances were the most common initial presentations with a prevalence of 51.1% (95% CI: 48.4-53.7) and 47.0% (95% CI: 44.4-49.7), respectively.

CONCLUSION

Isfahan could be considered as an area with a medium to high risk of MS. This is in sharp contrast with the gradient hypothesis.

Co-occurrence of autoimmune thyroid disease in a multiple sclerosis cohort

Background

Multiple sclerosis (MS), Hashimoto's disease and Graves' disease are autoimmune diseases that may share similar pathogenic mechanisms. The co-occurrence rates and demographic characteristics of Graves' disease and Hashimoto's disease (HT) in our MS population are compared with the general population.

Methods

The prevalence of thyroid disease in our MS patients was determined by chart review and survey. Previous diagnosis of thyroid disease, age at diagnosis, treatment used, and about the use of disease modifying medications used to treat their MS were asked. Chart reviews were used to estimate the population prevalence of Graves' disease and Hashimoto's disease and to estimate the demographics of patients with thyroid disease.

Results

A significant co-occurrence of Graves' disease with MS (p = 0.002), and a non-significant co-occurrence of Hashimoto's disease were noted (p = 0.097). No difference in the age of onset or gender of thyroid disease in MS patients compared to the general population was found.

Conclusion

There is a significant co-occurrence in patients with MS and Graves' disease, and a trend to co-occurrence in patients with MS and Hashimoto's disease. There are no differences in the demographics of patients with thyroid disease in our MS patients compared to the general population.