The frequency of multiple sclerosis in Italy: a descriptive study in Ferrara

The Increased Susceptibility of Women to Multiple Sclerosis

Many diseases with an auto-immune etiology have a skewed sex distribution. In the majority of instances, women are affected more frequently than men. A review of population studies demonstrates that the preponderance of women in multiple sclerosis (MS) is almost constant. We show that this preponderance is further increased in early as well as in late-onset cases, in familial cases as well as in MS twin pairs and that the HLA-DR2 allele, which has been associated with MS in Caucasian populations, is significantly more frequent in women than in men with MS. “Rules” have been established for multifactorial diseases; MS contravenes most of those rules. The skewed sex distribution in MS could be attributed to the known hormonal and gender influences on the immune response, as well as to genetic influences.

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.

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.

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.

Multiple sclerosis in Malta in 1999: an update

OBJECTIVES

To ascertain the prevalence of multiple sclerosis (MS) in the islands of Malta and compare it with a previous study undertaken 21 years earlier, when a remarkably low prevalence was found.

METHOD

Deaths with MS on the death certificate since the last study were reviewed. Sources of information about new patients were the Hospital Activity Analysis scheme, the MS Society of Malta, the records of the state hospitals, long stay private hospitals and nursing homes, lists provided by the state pharmacies, and magnetic resonance imaging, cerebrospinal fluid, and evoked response studies. Prevalence day was 1 January 1999. The Poser classification was used.

RESULTS

Since 1978, 17 patients had died with a verified diagnosis of MS on the death certificate. They included all 10 deaths with MS from the original study and two immigrants. Fifty patients had clinically definite MS (CDMS) and 13 clinically probable MS (CPMS). The prevalence of CDMS was 13.2/100 000 (male 11.2, female 15.2). The prevalence of CDMS and CPMS combined was 16.7/100,000 (male 13.3, female 19.9). The annual incidence was 0.7/100,000. Twelve patients were found with CDMS among the 7213 immigrants resident in Malta (166/100,000). The expected rate was 1/100,000, determined at Maltese born rates. There were major changes in the population distribution during the 21 years between the two studies, with a big increase in the age groups with a high risk of MS. There is a longer expectation of life and the diagnosis in now made earlier.

CONCLUSION

Malta still has a low MS prevalence. In comparison with Sicily and other Mediterranean countries of Europe it offers an opportunity to ascertain the genetic and environmental factors responsible for the disease.

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 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.

Epidemiology of multiple sclerosis

The inhomogeneous distribution of MS may represent an important clue about the cause of the disease. The prevalence of MS appears to be increasing in many regions of the world, although it is likely that in a majority of regions surveyed, this increase is attributable to differences in ascertainment over the relatively short period that MS has been surveyed worldwide, which is almost exclusively the last 50 years. MS occurs most frequently in regions populated by northern Europeans, and in these areas, it is much more common in the northern European population than in the indigenous populations. MS occurs in relatives of MS patients at a rate 10- to 50-fold greater than in the general population. On average, the absolute risk to a first-degree relative of an MS patient is 2% to 5%, depending on the exact degree of relatedness. Although the mode of transmission is not certain, a multigenic pattern best fits the observed pattern of transmission. A majority of monozygotic twins are discordant for MS, indicating that a major component of MS susceptibility is environmentally determined, although recent observations in adopted relatives suggest that this risk is not transmissible. Rare epidemics of MS involving small numbers of individuals in geographically isolated regions have been reported. A number of migrant studies suggest that the risk of acquiring MS may be altered by migration, although some also support genetic factors. Analytic approaches to address the role of various risk factors include ecologic studies, case-control studies, and cohort studies. Ecologic studies are best suited for addressing risk factors that influence overall population risk, whereas case-control studies are best suited for addressing risk factors that pertain to individuals within a population. If a risk factor is distributed homogeneously in a given population, a case-control study is insensitive to its effect. Improved methodology to diminish the biases inherent in case-control studies and identification of other important risk factors from basic scientific studies undoubtedly will be important for analytic epidemiologic studies of the future. Furthermore, analysis of highly informative populations, such as discordant identical twins and adoptive siblings of MS patients, likely will improve the specificity of case-control studies by minimizing the vast number of potential differences between cases and controls.

[Multiple sclerosis: clinical analysis and development of 214 cases]

The authors report on a series of 214 cases of defined multiple sclerosis according to Poser et al. criteria. These cases were retrospectively selected by medical reports analysed from Santa Casa Medical School (São Paulo) and the private practice, from 1980 to 1993. The data were analysed as for sex, race, onset age of symptoms, onset symptoms, and evolutive symptoms. The results were compared to those found in other Brazilian series and in foreign series. This comparative analysis allows to verify similarities and differences among the several series, and the authors emphasize the necessity of multicentric studies in Brazil to assert with more details the multiple sclerosis profile in our country.

Frequency of MS in the province of Modena, 1970-1990

Before 1975 the multiple sclerosis (MS) prevalence rate in Italy ranged from 4 to 21 cases per 100,000 inhabitants. In more recent studies the MS prevalence rate exceeded 30 cases per 100,000. We decided to perform an epidemiological survey in the province of Modena, Northern Italy, in order to clarify whether Italy should be considered as an area at high risk for MS like the countries of continental Europe. The mean annual incidence for the disease for the period 1970-1990 was 1.49 per 100,000, and the prevalence rate was 38.91 per 100,000 on December 31, 1990. These results indicate Modena is a high risk MS area.

Descriptive epidemiology of multiple sclerosis in Europe in the 1980s: a critical overview

The oversimplified but commonly accepted belief, based on the comparison of the prevalence studies conducted until 1980, that the distribution of multiple sclerosis (MS) in Europe is related to latitude has been contradicted by a great number of prevalence and incidence studies carried out since 1980. The most recent studies, based on more appropriate methods, clearly indicate that the MS distribution in Europe is much more complex than supposed in the past. The MS distribution in Europe now appears to be very uneven, with great variations not only between areas at the same latitude, but also within the countries themselves. However, even the most recent European studies cannot be reliably compared because of differences in the denominator characteristics, case ascertainment accuracy, diagnostic criteria, and definitions of prevalence and incidence. Despite these problems, descriptive data since 1980 indicate that ethnicity plays an important role in determining the European MS distribution. Furthermore, variations in both prevalence and incidence rates in ethnically homogeneous populations confirm the i importance of environmental factors in determining the primary acquisition of the disease. Further descriptive studies based on more comparable methods and better control for ethnicity would more precisely define the role of genetic susceptibility as well as suggest more valuable clues regarding environmental factors affecting the primary acquisition of MS.

The myelin basic protein gene is not a major susceptibility locus for multiple sclerosis in Italian patients

To verify whether multiallelic polymorphism adjacent to the gene encoding for myelin basic protein is associated with or linked to multiple sclerosis in Italians, we studied 54 sporadic patients, 55 control subjects and 18 families with two or more affected individuals. Allelic typing was carried out by analysis of fragment length polymorphisms after DNA amplification by the polymerase chain reaction. The presence of linkage with the disease was tested according to either autosomal dominant or autosomal recessive modes of inheritance, and with or without the introduction of liability classes accounting for the age of the individuals. Furthermore sib-pair analysis was performed in 11 siblings. No evidence for association or linkage between the myelin basic protein gene polymorphism and multiple sclerosis was found. Our data indicate that in the Italian population the myelin basic protein gene does not play a major role in conferring genetic susceptibility to multiple sclerosis, and suggest that the latter is a heterogeneous phenomenon, possibly influenced by the different ethnic origin of the populations which have been investigated.

Epidemiologic evidence for multiple sclerosis as an infection

The worldwide distribution of multiple sclerosis (MS) can be described within three zones of frequency: high, medium, and low. The disease has a predilection for white races and for women. Migration studies show that changing residence changes MS risk. Studies of persons moving from high- to low-risk areas indicate that in the high-risk areas, MS is acquired by about age 15. Moves from low- to high-risk areas suggest that susceptibility is limited to persons between about ages 11 and 45. MS on the Faroe Islands has occurred as four successive epidemics beginning in 1943. The disease appears to have been introduced by British troops who occupied the islands for 5 years from 1940, and it has remained geographically localized within the Faroes for half a century. What was introduced must have been an infection, called the primary MS affection (PMSA), that was spread to and from successive cohorts of Faroese. In this concept, PMSA is a single widespread systemic infectious disease (perhaps asymptomatic) that only seldom leads to clinical neurologic MS. PMSA is also characterized by a need for prolonged exposure, limited age of susceptibility, and prolonged incubation. I believe that clinical MS is the rare late outcome of a specific, but unknown, infectious disease of adolescence and young adulthood and that this infection could well be caused by a thus-far-unidentified (retro)virus.

Multiple sclerosis: does epidemiology contribute to providing etiological clues?

The epidemiological approach has undoubtedly contributed to our knowledge of Multiple Sclerosis (MS) by providing some etiological hypotheses in spite of the fact that a definitive basis for the conclusive resolution of its enigma is still lacking. Epidemiological studies have indicated that MS has an uneven geographical distribution and a changing incidence over time at least in several areas of the world: this suggests an etiological role of both genetic and environmental factors. The racial difference in disease risk, the results of familial and twin studies as well as the association between MS and some HLA markers, support the great importance of genetic factors. On the other hand, the evidence of temporal trends and the data from migrant studies seem to underline the etiological contribution of environmental factors. In the light of these results much of the present views have emerged interpreting the disease as caused by multiple factors acting at a susceptible age in genetically predisposed subjects.

Epidemiology of multiple sclerosis: a critical overview

The decisive conclusions to be drawn from the available epidemiological data, mostly geography and prevalence, of MS are: (1) a north-south (as well as west-east in the United States) gradient exists independent of genetic/racial factors; (2) major differences in prevalence occur in the absence of latitude differences; (3) individuals from the same ethnic derivation have either similar prevalence rates or very different prevalence rates in widely separated geographical areas and (4) specific resistant isolates are shown to exist regardless of latitude. Existing information leads to the almost inescapable conclusion that the epidemiology of MS cannot be explained by any single known environmental or genetic factor(s) in isolation. A combination of a heterogeneous distribution of both genetic and environmental factors appears to be required to explain the available data on MS.

HLA and multiple sclerosis in Italy: a review of the literature

HLA antigens of locus A, C, B, DR and DQ were typed in 104 Italian multiple sclerosis patients and in 905 healthy controls; the results have been compared with those published in the Italian literature. The Italian studies have been reviewed regarding the ethnic origin of the typed population and the corresponding prevalence of the disease. The data suggest a lack of association between A3 and B7 antigens and Italian multiple sclerosis and a relevance of other DR locus antigens (mainly DR4 and DR5), in addition to DR2, in the susceptibility to the disease.

Epidemiology of multiple sclerosis in northern Greece

A total of 638 new cases of multiple sclerosis (MS) (365 females, 273 males) were found from 1970-1984 in northern Greece (Macedonia and Thrace); the average annual incidence rate was 1.79 per 100,000 inhabitants with increasing incidence from 1980-1984. A total of 729 people living in northern Greece suffered from MS on December 31, 1984 (prevalence rate 29.5 per 100,000 inhabitants). No difference was found between urban and rural areas. No difference from the international standards was found for sex incidence. The study confirms the quite high prevalence of MS despite the fact that northern Greece is in the intermediate risk zone.

Epidemiological study of myasthenia gravis in the province of Ferrara, Italy

The only prevalence rate of myasthenia gravis (MG) so far estimated in Italy by an epidemiological study carried out in Pavia, North Italy, indicates a prevalence quite similar to that observed in other countries. The purpose of the survey was to verify the frequency of the disease in a geographically well-defined and previously surveyed community. On the basis of 39 cases, on 31 December 1987 the prevalence per million was 105.3 (102.3 if standardized for the Italian population). This is the highest prevalence figure yet found, indicating a value similar to that established in Northern Europe. According to Kurtzke this high prevalence rate reflects the high standard of the local public health service, which permitted a more intensive search for affected subjects.

Prevalence of every night snoring and obstructive sleep apnoeas among 30-69-year-old men in Bologna, Italy

An epidemiological survey of the prevalence of snoring and sleep apnoeas was performed on 3479 30-69-year-old men living in Bologna, north-east Italy. First a postal questionnaire was sent. It was returned with appropriate answers by 1170. A 20% random sample of those who did not answer were invited by telephone to return the questionnaire. Among these groups 119 (10%) and 19 (5.6%) respectively answered that they always snored. A random sample of 40 every-night snorers were studied by polysomnography. Based on the frequency of every-night snoring and the results of polysomnography we estimated that the minimal prevalence of sleep apnoea among 30-69-year-old men was 2.7% considering an apnoea + hypopnoea index of 10 or more pathological. According to the Lugaresi classification we had a 2.5% prevalence of heavy snorers' disease (HSD) Stage 1 or higher. These figures indicate that obstructive sleep apnoea during sleep is a major public health problem.

Geographical distribution of multiple sclerosis mortality in Spain

Mortality from multiple sclerosis in Spain has been analyzed for the period 1969-1979. In this period 1841 deaths from MS as primary cause were registered. The death rate decreased markedly during the first years, but was steady between 1975 and 1979 with 0.35 deaths per 100,000 population. This value places Spain within the low-medium risk zone of MS. The geographical distribution by provinces shows a slight northern predominance, with the highest rates in the northwestern area.

Multiple sclerosis in Europe

At a symposium held in conjunction with the 13th World Congress of Neurology, epidemiological data were presented from 23 European countries. In addition to the confirmation of the well-known north-south gradient, new details emerged on the high-prevalence areas of the British Isles and Scandinavia and on high-prevalence areas in some of the eastern and Mediterranean countries requiring more intensive exploration and confirmation. It became evident that higher prevalences existed in some places in Southern Europe previously thought to be regions of very low frequency. Limitations in the evaluation and comparison of data presented were obvious in view of differences in concepts, techniques and the intensity of surveys carried out. There was general agreement that this first collaborative attempt to map the frequency of multiple sclerosis in Europe should be followed up by standardized procedures and more cooperation in epidemiological surveys.

Sardinia, a high-risk area for multiple sclerosis: a prevalence and incidence study in the district of Alghero

Findings from small descriptive studies carried out in the last few years in Sardinia suggest that this region is now of high rather than medium risk for multiple sclerosis. It is uncertain whether this high prevalence reflects a different approach in case finding over time or a true change in disease occurrence. We report the results of a prevalence and incidence survey conducted in the district of Alghero, a community of 78,000 people in northwest Sardinia. Based on data from 31 patients, the average annual incidence for the period 1971 through 1980 was 4.1 per 100,000. On December 31, 1980, the prevalence rate was 59 per 100,000. The results support the view that Sardinia is now a high-risk area for multiple sclerosis, and further suggest a rise in the occurrence of the disease in recent years.