Multiple sclerosis in Italy. A reappraisal of incidence and prevalence in Ferrara

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.

Gender-related protection from or vulnerability to severe CNS diseases: gonado-structural and/or gonado-activational? A meta-analysis of relevant epidemiological studies

BACKGROUND

A vast scientific literature has dealt with gender-specific risk for brain disorder. That field is evolving toward a consensus to the effect that the estrogen hormone family is outstandingly and uniquely neuroprotective. However, the epidemiology relevant to this general outlook remains piecemeal.

METHOD

The present investigation strategically formats the relevant epidemiological findings around the world in order to quantitatively meta-analyze gender ratio of risk for a variety of relevant severe central nervous system (CNS) diseases at all three gonadal stages of the life cycle, pre pubertal, post adolescent/pre menopausal, and post menopausal.

RESULTS

The data quantitatively establish that (1) no single epidemiological study should be cited as evidence of gender-specific neuroprotection against the most common severe CNS diseases because the gender-specific risk ratios are contradictory from one study to the other; (2) risk for severe CNS disease is indeed significantly gender-specific, but either gender can be protected: it depends on the disease, not at all on the age bracket.

CONCLUSION

Our assay of gender-specific risk for severe brain disease around the world has not been able to support the idea according to which any one gender-prevalent gonadal steroid hormone dominates as a neuroprotective agent at natural concentrations.

Incidence and prevalence of multiple sclerosis in Europe: a systematic review

BACKGROUND

Multiple sclerosis (MS) is the most common cause of neurological disability in young adults worldwide and approximately half of those affected are in Europe. The assessment of differential incidence and prevalence across populations can reveal spatial, temporal and demographic patterns which are important for identifying genetic and environmental factors contributing to MS. However, study methodologies vary and the quality of the methods can influence the estimates. This study aimed to systematically review European studies of incidence and prevalence of MS and to provide a quantitative assessment of their methodological quality.

METHODS

A comprehensive literature search was performed to obtain all original population-based studies of MS incidence and prevalence in European populations conducted and published between January 1985 and January 2011. Only peer-reviewed full-text articles published in English or French were included. All abstracts were screened for eligibility and two trained reviewers abstracted the data and graded the quality of each study using a tool specifically designed for this study.

RESULTS

There were 123 studies that met the inclusion criteria. The study estimates were highly heterogeneous, even within regions or countries. Quality was generally higher in the more recent studies, which also tended to use current diagnostic criteria. Prevalence and incidence estimates tended to be higher in the more recent studies and were higher in the Nordic countries and in northern regions of the British Isles. With rare exceptions, prevalence and incidence estimates were higher in women with ratios as high as 3:1. Few studies examined ethnicity. Epidemiological data at the national level was uncommon and there were marked geographical disparities in available data, with large areas of Europe unrepresented and other regions well-represented in the literature. Only 37% of the studies provided standardized estimates.

CONCLUSIONS

Despite the breadth of the literature on the epidemiology of MS in Europe, inter-study comparisons are hampered by the lack of standardization. Further research should focus on regions not yet studied and the evaluation of ethnic differences in MS prevalence and incidence. National-level studies using current diagnostic criteria, validated case definitions and similar age- and sex-standardization would allow better geographical comparisons.

Incidence of multiple sclerosis among European Economic Area populations, 1985-2009: the framework for monitoring

Background

A debate surrounding multiple sclerosis epidemiology has centred on time-related incidence increases and the need of monitoring. The purpose of this study is to reassess multiple sclerosis incidence in the European Economic Area.

Methods

We conducted a systematic review of literature from 1965 onwards and integrated elements of original research, including requested or completed data by surveys authors and specific analyses.

Results

The review of 5323 documents yielded ten studies for age- and sex-specific analyses, and 21 studies for time-trend analysis of single data sets. After 1985, the incidence of multiple sclerosis ranged from 1.12 to 6.96 per 100,000 population, was higher in females, tripled with latitude, and doubled with study midpoint year. The north registered increasing trends from the 1960s and 1970s, with a historic drop in the Faroe Islands, and fairly stable data in the period 1980-2000; incidence rose in Italian and French populations in the period 1970-2000, in Evros (Greece) in the 1980s, and in the French West Indies in around 2000.

Conclusions

We conclude that the increase in multiple sclerosis incidence is only apparent, and that it is not specific to women. Monitoring of multiple sclerosis incidence might be appropriate for the European Economic Area.

Multiple sclerosis in Italy: cost-of-illness study

This study estimates the direct costs of multiple sclerosis (MS) in Italy from the perspective of the National Health System. Patients diagnosed with MS for ≥1 year prior to study entry were included in the analysis; neurological disability was assessed using the Expanded Disability Status Scale (EDSS). Cost variables were analyzed according to: MS phenotype, disease course over the previous year and EDSS rating. A total of 510 patients were included in the analysis. Overall costs were significantly higher for relapsing-remitting MS and secondary progressive MS than for primary progressive MS (P < 0.05). Costs were higher for EDSS scores 0.0-3.5 and 4.0-6.0 than for scores > 6.0 (P < 0.05). The extrapolated data gave an estimated annual direct cost of MS per patient of <euro>18,030. In conclusion, relapsing-remitting MS or secondary progressive MS phenotypes and lower estimated EDSS scores appear to be associated with higher costs.

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.

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.

Gender differences in health-related quality of life in multiple sclerosis

Women have about twice the risk of developing multiple sclerosis (MS) compared with men, a ratio that seems to be increasing. Most studies show that female patients seem to have a more favourable outcome of the disease. We studied the gender-specific impact of MS on health-related quality of life. We surveyed the population prevalence of MS patients in Ferrara, Italy. Data were extracted from the MS registry of the study area. Health-related quality of life was assessed using the MSQOL54 questionnaire. We analysed 370 patients (105 men and 265 women). They had worse scores than the general population in all health-related quality of life dimensions, ranging from 2.5 standard deviations (SD) lower for physical functioning to less than 0.5 standard deviations for mental health. Health-related quality of life scores were inversely correlated with disability scores. The impact of disability on health-related quality of life was higher for men than women regarding physical functioning (p < 0.01), vitality (p < 0.001), social functioning (p < 0.001), emotional wellbeing (p < 0.05) and mental health (p < 0.01). For scales reflecting mental health, a marked reduction with increasing disability was seen for men, while a linear reduction in the range of Expanded Disability Status Scale score 0—5 was reported for women, followed by no clear decrease for higher scores. We conclude that MS affects health-related quality of life in all of its dimensions. The impact of disability seems to be stronger among men, in particular for scales related to mental well-being. This could indicate that interventions should to be gender specific in order to better meet patients’ needs.

Temporal trends in the incidence of multiple sclerosis: a systematic review

BACKGROUND

Multiple sclerosis (MS) has been traditionally considered to be more frequent in women and in regions more distant from the equator. However, recent reports suggest that the latitude gradient could be disappearing and that the female-to-male ratio among patients with MS has increased in the last decades. We have conducted a systematic review of incidence studies of MS to assess the overall incidence of MS and explore possible changes in the latitude gradient and the female-to-male ratio over time.

METHODS

Systematic review of incidence studies of MS published in Medline between 1966 and February 2007. Age- and sex-specific incidence rates were collected from eligible publications. We computed age-adjusted rates using the world population as standard, and assessed differences in rates according to latitude and period of case ascertainment. Additionally, we evaluated the association between period of case ascertainment and the female-to-male ratio.

RESULTS

The overall incidence rate of MS was 3.6 cases per 100,000 person-years (95% CI 3.0, 4.2) in women and 2.0 (95% CI 1.5, 2.4) in men. Higher latitude was associated with higher MS incidence, though this latitude gradient was attenuated after 1980, apparently due to increased incidence of MS in lower latitudes. The female-to-male ratio in MS incidence increased over time, from an estimated 1.4 in 1955 to 2.3 in 2000.

CONCLUSION

The latitude gradient present in older incidence studies of multiple sclerosis (MS) is decreasing. The female-to-male MS ratio has increased in the last five decades.

Prevalence and incidence of multiple sclerosis in Salerno (southern Italy) and its province

Many multiple sclerosis (MS) prevalence studies in Italian northern and central areas, since 1980, have put Italy in a high risk zone; none concerns southern Italy. The MS registry of Salerno Center was reviewed, including the city and 16 towns at different distances (9-149 km) better connected to our Center. Population screened: 259 681 persons (Salerno = 136 678; province = 123 003). Prevalence day was December 31, 2005. Data on 186 patients were collected of which 55 were males, 131 females; crude total prevalence = 71.6263 (62.03-82.303, ranging from 50.1128 (Oliveto Citra) to 431.499 (Controne). Salerno prevalence rate is 70.9697 (57.41-86.583); standardized = 72.02. Incidence rate ranges from 2.38585 (1.6-3.39) (1991-95) to 4.31997 (3.24-5.6) (2001-05). Our data can be underestimated because some patients could have skipped the local center. This emphasizes that the results, except for Sardinia, are comparable to Italian literature data. They confirm that this territory is a high risk area for MS. There is also an indirect indication against a latitude gradient for 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.

Incidence of multiple sclerosis in the United Kingdom

Existing data on the incidence of multiple sclerosis (MS) in the UK have some limitations. Few studies have reported age- and sex-specific incidence rates of MS, and none of those is based on a large sample of the general population. Further, no published reports have provided age- and sex-specific incidence rates of MS by clinical course from onset. To estimate the age- and sex-specific incidence rate and lifetime risk of multiple sclerosis, we identified all new cases of MS during the period 1993-2000 in the General Practice Research Database, which includes health information on over three million Britons. Based on 642 incident cases, incidence rates of MS adjusted to the world population were 7.2 (95 % CI 6.5, 7.8) in women and 3.1 (95 % CI 2.6, 3.5) in men. The incidence of MS with relapsing-remitting onset was higher in women than in men (incidence rate ratio 2.5, 95% CI 2.1, 3.1), but there were no sex differences for primary-progressive MS (incidence rate ratio 1.1, 95% CI 0.7, 1.8). The estimated lifetime risk from birth of receiving an MS diagnosis was 5.3 per 1,000 in women and 2.3 per 1,000 in men. These results confirm the relatively high incidence of MS in the UK and show marked differences in the sex-specific pattern of MS incidence by clinical course from onset.

Western and Asian features of multiple sclerosis in Mexican Mestizos

OBJECTIVES

The objective of this study was to compare the clinical expression of MS in Mexican Mestizos with that of patients of European or Asian descent; as well as to compare the annual frequency of new cases with that observed in the previous decades.

PATIENTS AND METHODS

All patients with diagnosis of definite MS seen at the National Institute of Neurology and Neurosurgery of Mexico from January 1993 to December 2003 were studied (n=312). Sociodemographic and clinical characteristics were compared with reports of patients from either Western or Asian origin; the long-term disability score was analyzed according to gender, age of onset of MS and the initial symptom.

RESULTS

The clinical expression of MS in Mexican Mestizos shares some characteristics with both, Asian and Western forms of MS indicating that the genetic composition of Mexican Mestizos participates in the clinical expression of the disease. Also, at the prevalence date, the mean age of patients and the duration of the disease were lower in our patients than in MS patients from endemic countries suggesting a true increasing incidence in recent times, rather than only improved case ascertainment.

CONCLUSIONS

Clinical expression of MS in Mexican Mestizos shows the coexistence of some features common in European and in Asian cases.

The epidemiology of multiple sclerosis in Europe

Multiple sclerosis (MS) is a chronic and potentially highly disabling disorder with considerable social impact and economic consequences. It is the major cause of non-traumatic disability in young adults. The social costs associated with MS are high because of its long duration, the early loss of productivity, the need for assistance in activities of daily living and the use of immunomodulatory treatments and multidisciplinary health care. Available MS epidemiological estimates are aimed at providing a measure of the disease burden in Europe. The total estimated prevalence rate of MS for the past three decades is 83 per 100,000 with higher rates in northern countries and a female:male ratio around 2.0. Prevalence rates are higher for women for all countries considered. The highest prevalence rates have been estimated for the age group 35-64 years for both sexes and for all countries. The estimated European mean annual MS incidence rate is 4.3 cases per 100,000. The mean distribution by disease course and by disability is also reported. Despite the wealth of epidemiological data on MS, comparing epidemiological indices among European countries is a hard task and often leads only to approximate estimates. This represents a major methodological concern when evaluating the MS burden in Europe and when implementing specific cost-of-illness studies.

Bayesian mapping of multiple sclerosis prevalence in the province of Pavia, northern Italy

The geographical analysis of a disease risk is particularly difficult when the disease is non-frequent and the area units are small. The practical use of the Bayesian modelling, instead of the classical frequentist one, is applied to study the geographical variation of multiple sclerosis (MS) across the province of Pavia, Northern Italy. 464 MS-affected individuals resident in the province of Pavia were identified on December 31st 2000. The overall prevalence was 94 per 100,000 inhabitants. This estimate indicates an increasing MS prevalence in the province, in accordance with the vast majority of the Italian areas where prevalence studies have been repeated. We mapped the geographical variation of MS prevalence across the 190 communes of the province both with a classical approach and a Bayesian approach. The frequentist approach produced an extremely dishomogeneous map, while the Bayesian map was much smoother and more interpretable. Our study underlines the usefulness of Bayesian methods to obtain reliable maps of disease prevalence and to identify possible clusters of disease where to carry out further epidemiological investigations.

The prevalence of multiple sclerosis in the District of Santarém, Portugal

The prevalence of multiple sclerosis (MS) in Portugal is still unknown. Recent studies conducted in southern European countries showed higher than expected rates of MS prevalence. In an attempt to evaluate the MS prevalence in Santarém--a district with 62621 inhabitants (1991 census) located in the centre of Portugal--we have conducted a population survey in this district for five years. The crude prevalence rate found was 46.3/100,000. This figure is not different from findings recently reported in studies conducted at similar latitudes in neighbour southern European countries. This was the first population survey conducted in Portugal, and it is the first accurate contribution to the knowledge of the MS prevalence in this country.

Increasing Incidence of Multiple Sclerosis in the Province of Sassari, Northern Sardinia

Sardinia is a high-risk area for multiple sclerosis (MS), with prevalence rates of 150 per 100,000 population. The study included 689 MS patients (female-male ratio 2.6) with disease onset between 1965 and 1999 in the province of Sassari. The mean annual incidence rate increased significantly from 1.1 per 100,000 population in 1965-1969 to 5.8 in 1995-1999, with no significant difference for gender and province sub-areas. The mean age at onset increased significantly during the same period from 25.7 to 30.6 years, while the proportion of patients with progressive initial course declined over time. The marked increase of MS incidence and the change of MS clinical phenotype over time cannot be explained by ascertainment bias only, thus pointing to a corresponding change in the distribution of exogenous risk factors in this highly genetically stable population.

Mortality Trends of Multiple Sclerosis in Spain, 1951–1997: An Age-Period-Cohort Analysis

Trends of multiple sclerosis mortality in Spain from 1951 to 1997 are examined. Age-adjusted mortality strongly decreased from 3.08 per 100,000 women in 1951-1967 to 0.59 in 1968-1980 (similar figures were obtained for men). This decrease seems to be due to an artifact produced by changes in codification of causes of death. An age-period-cohort analysis, limited to the period 1968-1997, showed that the mortality trend in Spain cannot be fully explained by year of death (period effect), but that a cohort (year of birth) effect is also necessary. An increase in mortality related with the cohort of birth was detected: people born after 1953 had double the risk of those born between 1938 and 1947, and four times the risk of those born between 1923 and 1932. Regarding the period effect, there is a decrease in mortality, probably due to improvements in life expectancy of multiple sclerosis patients.

The prevalence of multiple sclerosis in the north?west Italian province of Genoa

The objective of this study was to assess the prevalence of multiple sclerosis (MS), calculated as point prevalence on 31 December 1997, in the province of Genoa, North-western Italy.

METHODS

The province of Genoa is located in North-western Italy, an area of 1,835 km(2). On the point prevalence day the population consisted of 913,218 inhabitants. MS cases were identified by analysing archives of the hospitals with neurological or rehabilitation wards, neurologists serving the community, files of local chapters of the Italian MS society, all requests for oligoclonal bands analysis on CSF in the studied area. Patients included in the study were MS cases diagnosed before 31 December 1997 according to the Poser criteria resident in the province under study.

RESULTS

A total of 857 subjects were alive and residing in the province of Genoa on the prevalence day. The overall crude prevalence rate was 94 per 100,000 (95% CI 88-100); 291 were males (34%) with a crude prevalence of 67 per 100,000 (95 % CI 60-76) and 566 were females (66%) with a prevalence of 118 per 100,000 (95% CI 108-128). The female/male ratio was 1.9. When age and sex were adjusted to the Italian standard population of 1991 prevalence was 85 per 100,000. Five hundred and thirty two out of the 857 patients agreed to be interviewed. The interviewed sample was representative of the prevalence sample: sex and gender distributions were identical in the two samples. The overall mean age was 48 (+/-13) years (48 +/-12 years in males; 48+/-14 years in females). Mean disease duration was 15 (+/-10) years for males and 16 (+/-11) years for females. Two hundred and ninety one (55 %) subjects had a relapsing remitting (RR) clinical course, 150 (28%) were secondary progressive (SP) and 91 (17%) were primary progressive (PP). Mean EDSS score was 5 (+/- 2; median 5). The mean age at time of onset was 33 (+/-10) years for males and 32 (+/- 11) years for females. The disease onset was monosymptomatic in 76% (n=407) patients and polysymptomatic in 24% (n=125). The mean length of time between clinical onset and diagnosis was 5 (+/- 6) years.

CONCLUSION

We confirmed that the province of Genoa is a very high risk area for MS. We found a high rate of patients with a PP course; also the proportion of patients with high disability scores is greater compared to previous studies.

Multiple sclerosis in twins from continental Italy and Sardinia: A nationwide study

Knowledge about the balance between heritable and nonheritable risk in multiple sclerosis (MS) is based on twin studies in high-prevalence areas. In a study that avoided ascertainment limitations and directly compared continental Italy (medium-prevalence) and Sardinia (high-prevalence), we ascertained 216 pairs from 34,549 patients. This gives a twinning rate of 0.62% among MS patients, significantly less than that of the general population. In continental Italy, probandwise concordance was 14.5% (95% confidence interval, 5.1-23.8) for monozygotic and 4.0% (95% confidence interval, 0.8-7.1) for dizygotic twins. Results in Sardinia resemble those in northern populations but in limited numbers. Monozygotic concordance was 22.2% (95% confidence interval, 0-49.3) probandwise, but no concordant dizygotic pairs were identified. A questionnaire on 80 items possibly related to disease cause was administered to 70 twin pairs, 135 sporadic patients, and 135 healthy volunteers. Variables positively (7) or negatively (2) associated with predisposition and concordance in twins largely overlapped and were mainly linked to infection. If compared with previous studies, our data demonstrate that penetrance in twins appears to correlate with MS prevalence. They highlight the relevance of nonheritable variables in Mediterranean areas. The apparent underrepresentation of MS among Italian twins draws attention to protective factors, shared by twins, that may influence susceptibility.

Genes, environment, and susceptibility to multiple sclerosis

Multiple sclerosis (MS) is a chronic disease of the central nervous system affecting young adults and thus representing a major burden also for their families and communities. The etiology of MS is obscure and its pathogenesis is yet incompletely depicted. Increased evidences indicate a strong genetic contribution to MS susceptibility, although others support the view that it is also influenced by environmental factors, possibly related to still unidentified pathogens. MS appears to be more heterogeneous than previously believed at the immunological level, and new pathological studies indicate a series of subset of conditions under the common denominator MS. The use of genetically homogeneous and geographically isolated populations at high MS risk, such as that of Sardinia, insular Italy, becomes in principle a vital requirement to reduce biological variables and the intrinsic complexity of the disease. This review will focus on recent findings on the peculiarity of Sardinian MS concerning epidemiological, genetic, and environmental aspects. Epidemiological studies reveal a clear heterogeneous distribution of MS cases in the Northern province of Sassari which may not be uniquely assigned to genetic variations. Furthermore, a different immunogenetic profile, including the association with other immunomediated diseases, and a progressive change in clinical phenotype, including age at onset, are present in this island which gives us unexpected variations at the level of patients' cohort and territorial distribution, especially when the northern province is compared to the southern one. This renders MS etiopathogenesis more complex than formerly thought even in this selected and genetically stable population.

Prevalence and incidence of multiple sclerosis in Las Palmas, Canary Islands, Spain

OBJECTIVES

To determine the prevalence and incidence of multiple sclerosis (MS) in the city of Las Palmas (Canary Islands, Spain), geographically belonging to north-western Africa, but with European ancestry.

METHODS

This population-based survey was conducted for a period of 5 years (1998-2002) in a Sanitary District of Las Palmas city (28 degrees 20' N), with a population of 82,623 inhabitants. Multiple sources were periodically investigated for case ascertainment. Patients with definite and probable MS were included.

RESULTS

Sixty-four patients with MS were identified on prevalence day, December 31, 2002. According to Poser's criteria the crude prevalence rate was 77.5 per 100,000 (95% CI: 59.7-98.9). This rate decreased to 73.8 (95% CI: 56.5-94.8) according to McDonald's criteria. Age-adjusted rates for the world and European standard populations were 61.6 (95% CI: 47.1-78.9) and 70.6 (95% CI: 55-89), respectively. Prevalence was higher for women aged 25-44 years. In 17 patients onset of MS occurred within the study period. Average annual incidence was 4.1 per 100,000 (95% CI: 2.4-6.6).

CONCLUSIONS

The prevalence and incidence rates in Las Palmas city are close to those reported from Continental Spain and other countries of southern Europe with similar social and ethnic background. These results highlight the role of racial-ethnic factors in the genesis of MS.

Cost-Analysis of Relapsing-Remitting Multiple Sclerosis in Italy after the???Introduction of New Disease-Modifying Agents

BACKGROUND AND OBJECTIVE

During the last decade, several agents have proven to be effective in the treatment of relapsing-remitting multiple sclerosis (RRMS), for example interferon-beta (IFNβ) and glatiramer acetate. This study aimed to perform a cost-analysis of the treatment of patients with RRMS in Italy after the introduction of these new agents.

STUDY DESIGN

This was a retrospective observational study with systematic patient inclusion.

METHODS AND RESULTS

Data gathered from 630 patients with confirmed RRMS over a 2-year period were evaluated. Overall, the direct cost over 2 years reached €11 073 100 thousand, corresponding to a per-patient cost of €17 576 (year of costing, 2001). The cost of disease-modifying agents represented approximately 77% of the total expenditure. IFNβ accounted for 94% of the expense of disease-modifying agents, corresponding to a 2-year cost per patient of €20 223. Although glatiramer acetate and immunoglobulins were also associated with a high level of expense, these were prescribed in only 3.8% and 1.1% of patients, respectively. Using regression analyses, IFNβ therapy, disability, number of days spent in hospital per year and the frequency of magnetic resonance imaging procedures were the main predictors of total costs.

CONCLUSION

Based on the results of this study, IFNβ treatment considerably modified the management of RRMS and was associated with a rise in cost of treatment per patient.

Prevalence of multiple sclerosis in Asahikawa, a city in northern Japan

Twenty-two years after the first survey, a follow-up study was performed on the prevalence of multiple sclerosis (MS) in Asahikawa, a city in northern Japan. The crude prevalence of MS rose from 2.5/100,000 (in 1975) to 10.2/100,000 (in 2002). The clinical diagnosis was established using the Poser diagnostic criteria, and the degree of physical disability was determined using the Expanded Disability Status Scale (EDSS). The distribution of patients according to the clinical form of MS was 65% with relapsing-remitting MS, 19% with secondary chronic progressive MS and 16% with the primary chronic progressive forms of MS. Symptoms at onset in the present study less often affected optic nerves (3%) than previously reported in Japan and was more like that seen in western MS series. Although prevalence of MS increase four-fold in Japan over the last two decades, it remains uncertain whether this apparent increase is real or reflects better ascertainment.

A genomic screen of Spanish multiple sclerosis patients reveals multiple loci associated with the disease

In order to identify the genomic regions that might confer susceptibility to multiple sclerosis (MS) in the Spanish population, we have performed a genome-wide screen for association in patients with MS using pooled DNA from 200 clinical cases and 200 healthy controls. The pools were typed using 5546 microsatellites. The typing was repeated for the most promising 1269 markers after which 191 potentially associated markers were identified. Eleven of these markers map to the MHC region, and 14 to non-MHC regions identified in previous linkage screens. Our results provide support for the presence of multiple coding regions that contain MS susceptibility genes of small or moderate effect.

Increasing frequency of multiple sclerosis in Padova, Italy: a 30 year epidemiological survey

OBJECTIVE

To determine the incidence and prevalence rates of multiple sclerosis (MS) and their temporal profiles over the last 30 years in the province of Padova (northeast Italy).

BACKGROUND

In the early 1970s an epidemiological survey in the province of Padova showed a MS prevalence and incidence of 16/100 000 and 0.9/100 000 population, respectively; these figures are much lower than current estimates in other regions of Italy and Central Europe.

METHODS

The population of the study area was approximately 820 000 (422 028 women, 398 290 men) in the 1991 census. All possible sources of case collection were used, but only clinically definite/probable and laboratory-supported definite/probable MS were considered in the analysis of incidence and prevalence trends from 1971 to 1999.

RESULTS

On 31 December 1999, the crude prevalence rate was 80.5/100 000 (95% CI 70.3-90.7); prevalence was higher in women (111.1/100 000; 95% CI 99.0-123.1) than in men (49.7/100 000; 95% CI 41.3-58.1). This difference was significant (F/M = 2.43; z = 10.1, P < 0,00001); a rate adjusted for the European population was 81.4/100 000. On 31 December 1980 and on 31 December 1990 the estimated prevalence rates were 18/100 000 and 45.7/100 000, respectively. Thus, a fivefold increase in prevalence was observed from the 1970s. The mean annual incidence was 2.2/100 000 in the period 1980-89, 3.9 in the period 1990-94 and 4.2 in the period 1995 99. Thus, incidence increased more than fourfold from the 1970s through 1994 and remained quite stable in the last several years. Mean age at onset was 31.3 +/- 9.88 years. Mean diagnostic latency decreased significantly from 49.2 +/- 44.5 months in 1985 to 23.0 +/- 30.3 months in 1990, 12.9 +/- 15.61 in 1995 and 5.3 +/- 4.7 in 1999.

CONCLUSIONS

The actual prevalence (80.5/100 000) and incidence (4.2/100 000) of MS in the province of Padova agree with the most recent epidemiological estimates/trends observed in other Italian and European areas, except for Sardinia and Scotland. The increase in both incidence and prevalence rates observed in much of this region over the last 30 years parallels the introduction of more sensitive diagnostic techniques and a highly significant decrease in diagnostic latency. These findings probably do not support a real increase in the frequency of MS in northeast Italy because recent estimates of incidence have increased only slightly (3.9 to 4.2, which is < 10% in five years) and increase in the prevalence rate was almost completely due to the accumulation of new incidence cases.

Multiple sclerosis complexity in selected populations: the challenge of Sardinia, insular Italy

Several lines of evidence indicate a genetic contribution to multiple sclerosis (MS) both in terms of predisposition to the disease and of immunological mechanisms which are known to play crucial roles in MS pathogenesis. The presence of high- and low-risk areas for MS in neighbouring regions supports the theory that MS predisposition is influenced by a complex interaction of genetic and environmental factors. Therefore, the use of genetically homogeneous and geographically isolated populations becomes an increasing requirement to reduce biasing biological variables. Sardinians fulfil these conditions well because of their different phylogeny from Europeans and the unique selective pressures which shaped their genome. Sardinians display amongst the highest MS prevalence rates world-wide and increasing MS incidence rates over time. Also, MS in Sardinia is linked to distinct human leucocyte antigen (HLA) alleles and associated to different patterns of cytokine production from lymphoid cells of different HLA subtypes. In this context, recent findings and future perspectives on the peculiarities of Sardinian MS concerning genetic, immunological and epidemiological aspects are presented. So far, our results indicate that variations at the level of territorial distribution and HLA-association are present which render MS heterogeneous even in this ethnically homogeneous population.

Prevalence of multiple sclerosis in Belgrade, Yugoslavia

OBJECTIVES

To estimate the distribution of multiple sclerosis in the Belgrade population.

METHODS

All persons who were affected and/or died from multiple sclerosis (Poser's criteria), with residence in the Belgrade region had been collected from January 1, 1985 to December 31, 1996. Prevalence was adjusted by direct method, using world population.

RESULTS

From 1985 to 1996, 823 patients were suffering from multiple sclerosis. Sex ratio was 1:1.9. The mean age at onset was 32.2 +/- 9.8 years. A relapsing-remitting course of multiple sclerosis was reported in 50.7% patients, secondary progressive in 36.4%, patients, and primary progressive in 12.9% patients. On December 31, 1996, age-adjusted prevalence of multiple sclerosis in Belgrade was 41.5/100,000, 28.2/100,000 for males, and 54.1/100,000 for females. During the period studied, statistically highly significant increasing trend of multiple sclerosis prevalence was observed (P = 0.0001).

CONCLUSIONS

According to findings presented in this study, Belgrade is an area with high prevalence of multiple sclerosis.

Multiple sclerosis epidemiology in Sardinia: evidence for a true increasing risk

OBJECTIVES

To update prevalence and incidence rates of MS among Sardinians.

MATERIALS AND METHODS

The present work is a "spider" kind of population based survey, conducted over the interval 1968-97, on patients with MS (Poser criteria) living in the province of Sassari, Northern Sardinia (454,904 population).

RESULTS

A crude total prevalence rate of 144.4 per 100,000, an onset-adjusted prevalence rate of 149.7 per 100,000 and an average annual incidence rate of 8.2 for the period 1993-7 were found.

CONCLUSION

Repeated epidemiological assessments of MS in Sardinia over decades have shown that the island is at high risk for MS. The present work highlights that MS incidence in Sardinia has been increasing over time. Although a substantial and widely spread improvement in MS case ascertainment can be postulated as the reason for such observations, a comparison between our data and those recently reported from a more industrialized province in Northern Italy seems to prove an at least partially real increase in MS risk among Sardinians and favours the hypothesis of a MS "Sardinian focus" as related to its latitude.

The increasing incidence and prevalence of MS in a Sardinian province

OBJECTIVE

To verify incidence rates and their temporal trend in a homogeneous, ethnically, and genetically distinct population of central Sardinia (the Nuoro province).

BACKGROUND

Intensive epidemiologic studies carried out in Sardinia since the 1970s have suggested that the prevalence and incidence of MS are much higher in this Mediterranean island compared with those found on mainland Italy.

METHODS

The study area had a population of approximately 274, 000 people in the 1991 census. The authors adopted a complete enumerative approach by reviewing all possible sources of case collection available in the investigative area.

RESULTS

Based on 469 MS patients, the mean annual incidence for 1955 to 1995 was 4.18 per 100,000 (or 4.3 per 100,000 if age- and sex-adjusted to the European population). The incidence, averaging 1.95 per 100,000 during 1955 to 1959, rose progressively over time, reaching rates of 6.6 in the quinquiennium 1985 to 1989 and 6.4 per 100,000 in 1990 to 1995. On December 31, 1994, the crude prevalence, based on 415 MS patients alive in the study area, was 151.9 per 100,000 (156.6 if adjusted to the European population).

CONCLUSION

These incidence and prevalence rates are the highest to date that have been estimated for a large community in southern Europe, and they constitute some of the highest rates in the world. Based on other surveys, these results reinforce the position of Sardinia as a higher and rising prevalence area for MS compared with other Mediterranean populations. Genetic and social-historic data strengthen the hypothesis of the environmental role and genetic factors among Sardinians in determining the notable difference in MS frequency between Sardinians and other Mediterraneans.

Prevalence of multiple sclerosis in the L'Aquila district, central Italy

OBJECTIVE

To estimate the prevalence of multiple sclerosis in the L'Aquila district, central Italy.

METHODS

All available case sources were screened. Definite and probable cases of multiple sclerosis, classified according to the Poser criteria, were considered as prevalent cases.

RESULTS

On the prevalence day, 31 December 1996, 158 patients (105 women and 53 men; ratio 2:1) affected by definite (n=131) or probable (n=27) multiple sclerosis were alive and resident in the L'Aquila district. Mean (SD) age was 38.4 (11.9) years (38.9 (11.7) years for women and 38.5 (12.3) years for men, p=0.9). The overall crude prevalence was 53.0/100 000 (95% confidence interval (95% CI)=45.4-62.0); 68.4/100 000 (95% CI=56. 5-82.8) in women, and 36.7/100 000 (95% CI=28.1-48.0) in men. The prevalence was similar (55.9/100 000) when standardised to the 1996 European population. Mean (SD) age at onset of multiple sclerosis was 29.4 (9.6) years and mean (SD) duration of the disease was 9.4 (7.4) years, without any significant difference between sexes. Mean age at onset was significantly higher in patients with the primary progressive than in those with the relapsing-remitting course (p=0. 0002, Scheffé's test).

CONCLUSIONS

The prevalence found in the L'Aquila district gives support to the consideration of Italy as an area in which multiple sclerosis has been shown to have high prevalence at least in the populations that were surveyed recently.

An epidemiological study of multiple sclerosis in central Sardinia, Italy

OBJECTIVES

To verify morbidity estimates in central Sardinia, Italy.

METHODS

A prevalence study was performed in the province of Nuoro, Central Sardinia, which has a population of 273,768 inhabitants (135,383 men and 138,385 women). A complete enumeration approach was adopted by using all possible case-collection sources.

RESULTS

On prevalence day, December 31, 1993, 394 subjects (124 men and 270 women) living in the study area were known to suffer from definite and probable MS, giving a crude prevalence rate of 143.9 cases per 100,000 people, 91.6 for males and 195.11 for females. The crude prevalence estimated on December 31, 1985, based on 282 MS cases alive in the study area, was 102.94 per 100,000.

CONCLUSION

This study reinforced central Sardinia's position as a high and rising prevalence area for MS.

Multiple sclerosis in Móstoles, central Spain

OBJECTIVES

Until relatively recently southern Europe was regarded as having a medium to low multiple sclerosis prevalence, of about 20 or less per 100,000. However, recent studies in Sardinia, Sicily, continental Italy, Cyprus and Spain have yielded higher MS prevalence rates, between 32 and 102.6 per 100,000. We present the results of a prevalence study of MS in the municipality of M6stoles, central Spain.

MATERIAL AND METHODS

To ascertain the prevalence of multiple sclerosis in M6stoles (195,979 inhabitants), an intensive study was undertaken using several sources of information. We used the Poser criteria in diagnosis.

RESULTS

There were 85 patients (53 women and 32 men) classified as definite or probable, prevalence 43.4/100,000 (95% CI, 34.7 to 53.7). The incidence rate was 3.8/100,000/year (95% CI, 2.7 to 5.3) in the last 5 years. Mean age on prevalence day was 38.8+/-10.9 years. Mean age at onset was 31.7+/-9.3 years. Mean interval between initial symptoms and diagnosis was 1.7 years. Mean duration of disease was 7.6+/-6.1 years. Overall, 70.6% had a relapsing-remitting course, 18.8% had a primary progressive and 10.5% had a secondary progressive. Mean EDSS score was 2.7+/-1.9.

CONCLUSION

The M6stoles study confirms the conclusions of previous smaller population studies that Spain is a moderately high or medium MS risk zone.