Epidemiology of multiple sclerosis: incidence and prevalence rates in Denmark 1948–64 based on the Danish Multiple Sclerosis Registry

The Danish Multiple Sclerosis Registry (DMSR) is a national register based upon the ethnically homogeneous Danish population of about 5 millions. The DMSR was founded in 1956 following a nationwide Danish prevalence survey of MS in 1949 and a continuous registration of incident cases of MS since January 1, 1948. Included in DMSR are all Danish cases of MS (or suspicion of MS) diagnosed by a neurologist or a department of neurology. The sources of notification are the 22 neurological departments in Denmark, the National Patient Registry, the neuropathological departments, the Registry of Causes of Death, and, up to 1975, the Disablement Insurance Court. Notified cases which do not comply with the standardized diagnostic criteria of the DMSR are excluded. An estimate of the completeness of the DMSR is 90-95% and the validity is around 94%. Age- and sex-specific incidence rates of MS for the interval 1948-64 are presented. The crude annual incidence rate of MS in Denmark was in the year 1948-64 4.42 per 100,000 population, 22% higher in females than males. There was a significant geographical variation of incidence rates and a significant downward trend in incidence rates during the interval, whereas the prevalence rates showed a slight increase.     

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.     

Multiple sclerosis in Oslo, Norway: prevalence on 1 January 1995 and incidence over a 25-year period

The Oslo Multiple Sclerosis (MS) Registry was established in 1990, and this is the first report on the prevalence and incidence of MS in the city of Oslo, Norway. The prevalence rate of definite MS on 1 January 1995 was 120.4/10(5). Inclusion of patients of native Norwegian ancestry only and exclusion of non-Norwegian immigrants yielded a prevalence rate of 136.0/10(5). A similar prevalence rate (136.5/10(5)) was found when patients and immigrants from the other Nordic countries (Finland, Sweden, Denmark) were included. Segregation of the native Norwegian patients according to the counties where they were born showed no significant differences except for a disproportionate increase of patients born in the inland county of Oppland. A total of 794 cases were resident in Oslo at the time of a diagnosis of definite MS in the period 1972-99. The crude average annual incidence rate for each 5-year period, between 1972 and 1996, increased significantly from 3.7/10(5) in the 1972-76 to 8.7/10(5) in the 1992-96 period. The increase was more marked in relapsing-remitting (RR) than in primary progressive disease and in female cases.     

Changes in multiple sclerosis epidemiology in Finland over five decades

Finland is a high-risk region for multiple sclerosis (MS) with several epidemiological studies on the subject published since 1964, but these have not been comprehensively scrutinized. The objective of this study was to review previous studies of Finnish MS epidemiology, introduce new data on MS prevalence in western parts of Finland and do further analyses on data from previous studies. We performed a systematic search on articles regarding MS epidemiology in Finland in PubMed database, and all relevant articles were included in this review. MS prevalences in the western hospital districts of Vaasa, South Ostrobothnia and Pirkanmaa were calculated in 1980-2007 by using previously unpublished data obtained from a retrospective search from hospital administrative registries. To enhance comparability of the epidemiological figures, we calculated age-standardized prevalence of MS from the new data from western hospital districts and previous data from North Ostrobothnia, Southwest Finland and North Karelia. Marked regional differences in MS epidemiology were confirmed with concentration of the disease in the western and south-western parts of the country. The highest regional age-standardized MS prevalence of 288/100 000 was reported in South Ostrobothnia in 2007. A clear and stable increase in MS prevalence was observed through the decades, but the only marked increase in incidence happened in 1990s. Methodological differences hampered direct comparisons of different studies, highlighting the importance of common principles of reporting and standardizing the epidemiological figures. More comprehensive studies on MS epidemiology are still warranted to yield important information concerning the aetiology of the disease.     

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 Gijon health district, Asturias, northern Spain

The objective of this study was to ascertain the prevalence and incidence of Multiple Sclerosis (MS) in a population of 33,775 in two primary health care centres in the sanitary district of Gijon, Asturias, northern Spain. Many information sources were used but the unique advantage of Gijon was that the city has a centralized computerized register of all diagnoses made for all consultations in the clinics and hospitals in the area. The HLA distribution in the population was already known and the Poser classification of MS was used. The crude MS prevalence was 65/100,000, a similar prevalence to that found in southern and eastern Spain, Sicily and Greek-speaking Cyprus. The mean incidence was 3.7/100,000 per year. The study demonstrated the advantage of a centralized and computerized medical recording system and demonstrates that northern Spain is a moderatelv high or medium MS risk zone.     

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 Móstoles, central Spain. Material and methods– To ascertain the prevalence of multiple sclerosis in Móstoles (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 Móstoles study confirms the conclusions of previous smaller population studies that Spain is a moderately high or medium MS risk zone.     

Multiple sclerosis in Chile

So far as we know this series of 68 cases is one of the first clinical accounts of multiple sclerosis in South America. Average age of onset was 30.7 years and female:male ratio was 2:1. The most frequent initial symptom was motor impairment and less frequent was visual loss. Most affected site of involvement in established cases was the optic nerve. There were no familial cases. The severity of the disease in Chile proved to be the same as elsewhere. No characteristic clinical pattern peculiar to the region emerged.     

Multiple sclerosis incidence in the Faroe Islands 1986–2007

Joensen P. Multiple sclerosis incidence in the Faroe Islands 1986–2007. Acta Neurol Scand: 2010: 121: 348–353.
© 2009 The Author Journal compilation © 2009 Blackwell Munksgaard. Objective – Epidemiological studies of the isolated Faroese population in 1945 identified a high annual incidence of multiple sclerosis (MS) of 10/100,000. At the time, there was speculation that the disease was brought to the country by British occupation forces resident in the islands from 1940 to 1945. The objective of the current study is to determine the incidence of diagnosis of MS in the Faroe Islands during the period 1986–2007. Methods – All patients in the Faroe Islands diagnosed with MS from July 1, 1986 to July 1, 2007 are documented in the current longitudinal, prospective study. The diagnosis is based on clinical observation, magnetic resonance imaging scanning, cerebrospinal fluid tests, and visual evoked potential response testing. Results – The incidence of MS during the period 1986–2007 is 4.5/100,000 annually. This is generally of the same order of magnitude as other research findings in Scandinavia and Iceland. The incidence of MS from 1986 to 2007 is about double the incidence in the Faroe Islands for the period from 1940 to 1986, calculated to be 2.7/100,000 annually. Conclusion – The observed incidence of MS in the Faroe Islands, where the population is genetically homogeneous and where the diet exposes the population to neuro‐toxic contamination, is at the same level as found in other high‐risk regions. The former detected epidemics of MS in Faroe Islands seems apparently to have leveled out and could not be recognized in the recent period covered by the present survey.     

Multiple sclerosis in Vest-Agder County, Norway

Vatne A., Mygland Å., Ljøstad U. Multiple sclerosis in Vest‐Agder county, Norway.
Acta Neurol Scand: 2011: 123: 396–399.
© 2010 John Wiley & Sons A/S. Objective – To examine multiple sclerosis (MS) prevalence, rate of immunomodulatory treatment and frequency of Borrelia Burgordorferi (Bb) antibodies in Vest‐Agder, Norway. Materials and methods – Patients in the period 1996–2006 who met the Poser criteria for definitive or probable MS were included. Clinical and demographical data, and presence of Bb antibodies were registered. Results – A total of 295 patients were identified. The crude prevalence was 180 per 100,000 population (95% CI = 160.9–218.0), age‐adjusted prevalence was 186 per 100,000 population (95% CI = 166.3–225.3). The age‐adjusted incidence rates were 7.5 and 8.0 for 1996–2000 and 2001–2006, respectively. Thirty‐eight per cent were treated with immunomodulatory agents when compared to 28% in the rest of the country. Bb serum antibodies were detected in 7% of patients with MS. Conclusions – Vest‐Agder county has the highest prevalence of MS reported in Norway, and a high treatment rate. Bb antibodies were not more prevalent than in healthy individuals.     

Multiple sclerosis in the two northernmost counties of Norway

The prevalence of MS in the two northernmost counties of Norway increased from 20.6 per 100,000 in 1973 to 31.5 per 100,000 in 1983, the increase being most marked in women. The average annual incidence seems to have been stable over the past 20-30 years. None of the patients had a pure Lapp background (having a Lapp mother and father).     

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 in the Canary Islands (Spain): a study on the island of La Palma

Objective: To determine the prevalence of multiple sclerosis (MS) on the Island of La Palma, Canary Islands, Spain. Methods: A population-based transverse study was carried out on the Island of La Palma (population: 81,507), from 1995 to 1998. The 15 December 1998 was established as prevalence day. Sources of information were periodically obtained from case records from public primary care centres, private hospitals, private centres, magnetic resonance units and others. In accordance with the Poser criteria all cases of definite or probable MS were included. Results: 34 cases of MS were found on prevalence day (9 male and 25 female): 32 cases were clinically definite and 2 were clinically probable MS. Crude prevalence was 42/100,000. Incidence during time of study was 2.25/100,000. Conclusions: The island of La Palma could be considered as an area of medium-high risk, the risk being higher than that expected because of the geographical latitude of the island. This study confirms the hypothesis of the high prevalence of MS in Spain. We have not found significant clinical differences in MS patients from those in other studies. Received: 7 August 2000, Received in revised form: 22 November 2001, Accepted: 16 April 2002 Correspondence to M. A. Hernández     

A possible spatial and temporal cluster of multiple sclerosis in the town of Linguaglossa,Sicily

We carried out an epidemiological survey to determine prevalence and incidence of multiple sclerosis in the little town of Linguaglossa in the Province of Catania. We calculated prevalence rate as point prevalence at 1 January 2001 and incidence during 1991–2000.We studied the frequency of multiple sclerosis in the community of Linguaglossa in a population of 5,422 inhabitants in the 2001 census. The primary sources for the case ascertainment were the general practitioners of Linguaglossa, the local Italian Multiple Sclerosis Association and the neurological departments, Multiple Sclerosis Centers and private neurologists of the province of Catania. We considered as prevalent and incident cases all patients who satisfied the Poser’s diagnostic criteria. We detected 11 patients with multiple sclerosis who had had the onset of disease on prevalent day (P.D.). The onset–adjusted prevalence rate was 203/100,000 (95% CI 107–352).Prevalence was higher in women (247/100,000) than in men (154/100,000). From 1991 to 2000, 10 subjects with MS had clinical onset of disease. The mean annual incidence risk was 18.2/100,000 (C. I. 95 % 5.9–42.5).Conversely in the same population prevalence on 1 January 1991 was 37/100,000 while the onset adjusted annual incidence risk during the previous decade (1981–1991) was 3.6/100,000. Prevalence and incidence rates of MS during the last decade in the little town of Linguaglossa are higher than those found in the same area during the previous ten years and also than those reported in other Sicilian and Italian surveys suggesting a possible cluster of MS.