Factors in the rising prevalence of multiple sclerosis in the north-east of Ireland

BACKGROUND: Northern Ireland is recognized as an area of high risk for multiple sclerosis. The original study of Allison and Millar in 1951 found a prevalence of 51/100,000 and mean annual incidence of 2.74/100,000/year. Subsequent studies in 1961, 1986, and 1996 suggested rising prevalence--80, 138, and 168.2/100,000, respectively. METHODS: In 2004, we surveyed the North-East of Northern Ireland (population 160,446, area 2030 km(2)) using multiple sources of case ascertainment, all satisfying the Poser criteria for definite or probable multiple sclerosis (MS) or the McDonald criteria. RESULTS: From a provisional list of 469 cases, 370 (123 males, 247 females) were identified. The prevalence was 230.6 per 100,000 (95% CI 207.0-255.4) with significantly higher prevalence in females (300.8/100,000) than males (157.0/100,000). Direct standardization to the 1961 Northern Ireland population reduced the overall prevalence rate to 200.5/100,000 (95% CI 193.2-208.0), in females to 270.2/100,000 (95% CI 258.8-282.4) and in males to 131.1/100,000 (95% CI 122.8-139.9). In 1996, incidence had risen to 9.3/100,000/year (14 cases in population of 151,000) with a higher incidence in females (10.3/100,000/year) than males (8.3/100,000/year). CONCLUSIONS: Northern Ireland continues to have a rising prevalence of MS. The increase in incidence suggests a true increase in the disease.     

Epidemiologic trends in multiple sclerosis in M?re and Romsdal, Norway: a prevalence/incidence study in a stable population

The western part of Norway has been a low-to medium-frequency area for multiple sclerosis (MS). The prevalence of definite/probable MS on January 1, 1961, was 24.3/100,000 in the county of M?re and Romsdal, western Norway. Based on the same diagnostic criteria, the prevalence of definite/probable MS increased to 75.4/100,000 on January 1, 1985. The average annual incidence rate increased from 1.94/100,000 in the period 1950-1954 to 3.78/100,000 from 1975-1979. Remitting MS in the younger age groups of both sexes increased the most. We consider this increase of MS to be due to alteration in exogenous factors as variation in genetic susceptibility cannot account for the increase in the stable western Norwegian population. The rise in prevalence/incidence over the last 20 to 25 years in western Norway supports the theory that MS is a disease influenced by exogenous factors that show variation over time.     

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

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

The frequency of multiple sclerosis in Mediterranean Europe

Recent investigations on multiple sclerosis (MS) distribution in Italy, based on relatively small population groups, contradict the current thesis, derived from studies undertaken in populations exceeding 300,000, of a lower spreading of the disease in Mediterranean Europe. Intensive surveys on small populations strengthen the suggestion that Italy is a high-risk area, although MS studies based on prevalence rather than incidence could also be biased by geographic variables making prevalence unsuitable for comparing MS prevalence rates found in different years and/or zones. We report a further epidemiologic study in Barbagia, Sardinia, insular Italy, undertaken both to establish the MS incidence in the last 20 years, and to estimate a new prevalence rate. Based on 31 probable incident cases, the mean incidence per year for the years 1961-1980 was 2.9 per 100,000 (3.2 if age- and sex-standardized to the Italian population). On October 24, 1981, the prevalence per 100,000 was 65.3 (77.9 if standardized to the Italian population). These results confirm that in Barbagia, MS occurs more frequently than expected in a Mediterranean area, and give further support to the idea that MS frequency in Italy is similar to that established for most central and northern European countries.     

High prevalence and fast rising incidence of multiple sclerosis in Caltanissetta, Sicily, southern Italy

BACKGROUND: Epidemiological studies conducted in Sicily and Sardinia, the two major Mediterranean islands, showed elevated incidence and prevalence of multiple sclerosis (MS)and a recent increase in disease frequency. OBJECTIVE: To confirm the central highlands of Sicily as areas of increasing MS prevalence and elevated incidence, we performed a follow-up study based on the town of Caltanissetta (Sicily), southern Italy. METHODS: We made a formal diagnostic reappraisal of all living patients found in the previous study performed in 1981. All possible information sources were used to search for patients affected by MS diagnosed according to the Poser criteria. We calculated prevalence ratios, for patients affected by MS who were living and resident in the study area on December 31, 2002. Crude and age- and sex-specific incidence ratios were computed for the period from January 1, 1993, to December 31, 2002. RESULTS: The prevalence of definite MS rose in 20 years from 69.2 (retrospective prevalence rate) to 165.8/100,000 population. We calculated the incidence of definite MS for the period 1970-2000. These rates calculated for 5-year periods increased from 2.3 to 9.2/100,000/year. CONCLUSION: This survey shows the highest prevalence and incidence figures of MS in the Mediterranean area and confirms central Sicily as a very-high-risk area for MS.     

Frequency of multiple sclerosis in Menorca, Balearic islands, Spain

OBJECTIVE: To establish prevalence and incidence of multiple sclerosis (MS) in Menorca (Balearic Islands, Spain; population: 67,009). METHODS: An extensive epidemiological study was undertaken using all available information sources. Patients were classified according to Poser's criteria. RESULTS: The prevalence rate of definite and probable MS was 68.6/100,000 (95% confidence interval 50.3-91.6). The incidence rate was 3.4/100,000/year (95% CI 2.2-5.3). The time lag between the first symptom and diagnosis was 10.2 years for patients with disease onset before 1987 and 2.1 years for patients with onset between 1987 and 1996. CONCLUSION: Menorca's population has a moderately high MS risk, with a prevalence rate the highest reported for a Spanish region.     

Multiple sclerosis in southern Europe: Monreale City, Italy. A twenty-year follow-up incidence and prevalence study

BACKGROUND: Several follow-up studies showed increasing prevalence and incidence rates for multiple sclerosis (MS). OBJECTIVE: To ascertain, throughout a follow-up study, the incidence and prevalence of MS in the city of Monreale, Sicily, southern Italy. METHODS: We calculated crude and age- and sex-specific prevalence rates on December 31, 2000, and determined incidence rates for the period January 1, 1992 to December 31, 2000. RESULTS: The prevalence of MS was 71.2 per 100,000 population (48,5/100,000 in men; 93,0/100,000 in women). The incidence rate of MS for the period 1992-2000 was 4.0/100,000 per year. CONCLUSION: This study showed a nonsignificant increase in MS incidence rates in Monreale city for 1992-2000 compared to 1981-1991. Prevalence rates were similar to those of the previous follow-up study. Intervals between onset of symptoms and diagnosis seemed shorter than in prior studies. There is no evidence that the high prevalence and incidence rates have changed in this interval but numbers are too small for firm statements. These findings indicate that in Monreale city MS prevalence is stable and confirm Sicily as a high-risk area for MS.     

Increasing prevalence and incidence of multiple sclerosis in northern Japan

BACKGROUND: We previously reported that prevalence of multiple sclerosis (MS) in Japan was 8.6/100,000 individuals in 2001. This was much higher than prevalence previously reported from Asian countries. A second epidemiologic survey was conducted to assess changes in MS prevalence and incidence over the last 30 years in Tokachi province of Hokkaido, the northernmost island of Japan. METHODS: The authors studied the frequency of MS in the community of Tokachi Province, where the population has stabilized between 350,000 and 360,000 over the last 30 years. The survey was conducted at the same institutions using the same methods as the first survey in 2001. RESULTS: On March 31, 2006, 47 subjects satisfied Poser's criteria for MS. The prevalence rate increased from 8.6 to 13.1/100,000 individuals between 2001 and 2006. The prevalence of conventional MS (C-MS) increased in five years although the prevalence of optic-spinal MS (OS-MS) did not increase. The mean annual incidence increased from 0.15 (1975-1989) to 0.68 (1990-2004). CONCLUSIONS: The results show the highest MS prevalence in Asia; the increase in MS prevalence in Tokachi Province may be due to increased incidence after 1990.     

Prevalence and incidence of multiple sclerosis in the city of Monreale, Italy

The prevalence and incidence of multiple sclerosis (MS) in the city of Monreale, southern Italy were ascertained 10 years after a preliminary study in the same area. The study was undertaken in a population of 26,256 people. The patients were classified according to Poser’s criteria. The prevalence of MS on 31 December 1991 was 72.4 per 100,000 population. The incidence of MS for the period 1981–1991 was 3.3/100,000 per year. The mean period between onset and diagnosis of MS was 4.9 years for those patients found during this survey and 9.2 years for those in the first study. This study shows an increase of MS prevalence in Monreale city and a high incidence. The findings parallel the reduction of the lag time between onset and diagnosis. Received: 25 March 1997 Received in revised form: 30 June 1997 Accepted: 10 July 1997     

An increase in the incidence of multiple sclerosis in Western Norway

Abstract– In the county of Hordaland, Western Norway, the prevalence of MS has been shown to have increased from 20/100,000 in 1963 to 60/100,000 in 1983. This study shows that the increase in prevalence was caused by a highly significant and marked increase in incidence over a 30-year period. The average annual incidence of about 2 per 100,000 population in 1953–1962 increased to 4 per 100,000 in the period 1968–1977. The rise in incidence was parallel for both sexes until 1970. In the last 10 years, the incidence has continued to increase among females, whereas a decrease has been observed among males.     

Epidemiology of multiple sclerosis in western Herzegovina

OBJECTIVES: To determine epidemiological rates of multiple sclerosis (MS) in western Herzegovina. PATIENTS AND METHODS: We analysed data from 81 MS patients (49 females, 32 males) on the prevalence day, 31 December 2003. Patient information was obtained from a search of all available medical records from the period 1994-2003 in the investigated area. RESULTS: Crude prevalence of MS was 27/100,000 (95% confidence interval (CI) 20-34). Prevalence was highest in the mountainous municipality of Posusje (56/100,000) and lowest in the coastal municipality of Neum (0 incidence). The annual incidence of MS was 1.6/100,000 (95% CI 0-3.3). The female/male ratio of MS was 1.5. The mean age of the patients on prevalence day was 40.0+/-11.6 years, and the mean age at disease onset was 31.0+/-7.1 years. Eight (10%) of the patients had a first-degree relative with MS. The primary progressive (PP) disease course was observed only in females. Visual symptoms were the initial symptom of MS in 6 (7%) of the patients. CONCLUSIONS: Western Herzegovina is an area of moderate risk for MS, and the distribution of MS in western Herzegovina is heterogeneous. PP-MS occurred only in females, and involvement of the visual pathways as the initial symptom of MS was low.     

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.     

Multiple sclerosis in the Republic of San Marino,Italian peninsula: an incidence and prevalence study from a high-risk area

Epidemiological studies on multiple sclerosis (MS) carried out in Southern Europe in the last years have shown a significant increase in the disease frequency. Previous surveys conducted in the Republic of San Marino, Northern Italian peninsula, identified that the population is at high risk for MS, with a prevalence of 51.6 per 100,000 population in 1982 and of 166.7 in 2005 and with a mean annual incidence of 7.9 per 100,000 for the period 1990–2005. The present work is a community-based intensive prevalence and incidence survey, by a complete enumeration approach, to update the prevalence and incidence of MS in the Republic of San Marino. The mean annual incidence for the period 2005–14 was 7.7 (95% CI 4.9–11.4) per 100,000, 3.3 (95% CI 1.1–7.6) for men and 11.9 (95% CI 7.2–18.6) for women. On 31 December 2014, 67 patients (19 men and 48 women), suffering from definite or probable MS and living in the Republic of San Marino, yielded a crude prevalence of 204.3 (95% CI 158.4–259.5) per 100,000, 117.8 (95% CI 70.9–183.7) for men and 288.2 (95% CI 212.4–383.3) for women. Our study has confirmed San Marino is an area at high risk for MS, in line with epidemiological data from continental Italy. The marked increase in MS prevalence over time in this population can be ascribable to increased survival and improved ascertainment, in the presence of a substantially stable, yet high, incidence rate.     

Epidemiological data of multiple sclerosis in the province of Evros,Greece

The frequency of multiple sclerosis (MS) in Greece is still debated. Our previous epidemiological field survey with a cross-check study of MS on March 31, 1984, in the province of Evros in north-eastern Greece showed a prevalence rate of 10.1/100,000. In 1990, Milonas et al. recorded a prevalence rate of 29.5/100,000 in northern Greece. So Greece is classified in the medium-frequency zone according to Kurtzke. This study was performed to estimate the prevalence of MS in the province of Evros and the annual incidence rates from 1974 to 1999. Patients were identified from several sources. A clinical follow-up was performed in 95% of the cases, and, if clinically indicated, new paraclinical examinations were performed and cases classified by Poser's criteria. The prevalence rate of the definite MS cases on December 31, 1999, was 38.9/100,000 and places the area in the high-risk zone. The mean annual incidence measured in 5-year intervals increased from 0.66/100,000 in 1974-1978 to 2.36/100,000 in 1994-1999 (p < 0.01). The increase in prevalence can be attributed to other causes than etiological changes, but the increase in the annual incidence rate indicates the possibility of a variation in risk factors of the disease.     

Trends in prevalence and incidence of multiple sclerosis in Bajo Aragón, Spain

OBJECTIVE: Recent reports provide consistent evidence that Spain is an area of high risk for multiple sclerosis (MS) according to prevalence surveys. However, the studies of incidence are scarce. The objective of the current work is to analyse whether the increased prevalence of MS is accompanied by increasing incidence in the area of Bajo Aragón, northeastern Spain. METHODS: The data of both prevalence and incidence were retrieved from a prospective register created in 1994 and which included patients with probable or definite MS. Crude and age-standardised rates were calculated from 1994 to 2002 and compared with those found retrospectively in the previous period of 1984-1993. RESULTS: In January 2003, we found a prevalence rate of 75/100,000 (95% CI: 52-97) whereas it was 35/100,000 (95% CI: 20-50) in 1994. In a period of 9 years, 25 new cases were diagnosed in the area with a mean annual incidence rate of 4.6/100,000 (95% CI: 2.8-6.5; range: 1.6-13.6) in comparison to 17 new cases from 1984 to 1993 with a mean incidence rate of 3/100,000 (95% CI: 1.6-4.5). The standardised ratio of incidences was 1.44 (95% CI: 0.95-2.17) and, therefore, the difference of rates was not significant. CONCLUSION: We conclude that the increase in prevalence of MS is more likely to be due to improvement on case ascertainment than to increasing incidence. Nonetheless, further prospective incidence studies in larger populations are warranted in Spain to elucidate whether the frequency of this disease is truly increasing.     

Multiple sclerosis in Istria, Yugoslavia

An epidemiological research of multiple sclerosis (MS) in Istria, Yugoslavia, was made in the period of 1980-1981. After examining all the sources of health care information, 125 potential MS patients were found in the investigated area. According to the diagnostic criteria by Schumacher et al., 47 affected were recognized and accepted as clinically definite MS patients. The MS prevalence rate in Istria on March 31st, 1981 amounted to 25.0/10(5) inhabitants (CI: 19.9-38.9). Such rates classify Istria in the middle between the medium and high risk zones for the disease in Europe and in the world. The onset age of MS in Istria was about 30 years, the female/male sex ratio was 2.13. The average duration of MS in Istria up to the prevalence day was 16.5 years. The average annual incidence rate was 1.5/10(5) inhabitants.     

Incidence of multiple sclerosis in the general population in the Netherlands, 1996-2008

Background: We estimated the multiple sclerosis (MS) incidence in the Netherlands for better active monitoring of potential vaccine safety signals. Methods: A retrospective cohort study (1996-2008) was conducted using a population-based general practice research database containing electronic medical records. Additional information was collected to validate incident probable cases. Results: In the source population (648,656 persons), 146 incident probable MS cases were identified. Overall incidence rate was 6.3/100,000 person years (py; 95% CI, 5.2-7.2). In the subgroup in which MS could be fully validated, the incidence increased from 4/100,000 py (95% CI, 3-5) in 1996-2004 to 9/100,000 py in 2007/8 (95% CI, 6-16). This increase was highest among women, but not statistically significantly different by gender. The median lag time between first recorded symptoms and MS diagnosis decreased from 32 months (<1998) to 2 months (>2005). Conclusions: MS is rare in the Netherlands. In recent years, there was a slight increase in the incidence especially among women during the fertile age. This increase coincided with a decrease in lag time between symptoms and diagnosis, both for men and women. This trend should be taken into account in the interpretation of MS cases occurring in a population where new vaccinations will be introduced shortly.     

Incidence of multiple sclerosis in Macomer, Sardinia, 1912-1981: onset of the disease after 1950

Intensive search of all cases of MS occurring in the Sardinian commune of Macomer since 1912 indicated that MS was absent up to the early 1950s. All 13 ascertained cases had clinical onset in the years 1952-1981. During this period, the average annual incidence was 4.8 per 100,000; the highest incidence was found in the period 1957-1961, slowly decreasing up to 1981. MS was probably introduced after 1945, when the centuries-old isolation of Macomer ended and the native population came into contact with individuals from high- and medium-risk areas.     

Prevalence of multiple sclerosis in the province of Teruel, Spain

There have been few reports about the frequency of multiple sclerosis (MS) in Spain. We undertook a prevalence study in the province of Teruel, which is served by two hospitals as referral centres for a population of 143,680. We found a total of 46 patients who fulfilled Poser’s criteria for clinically definite or probable MS with a prevalence rate of 32/100,000 [95% confidence interval (CI): 22.8–41.3]. The prevalence rates for males and females were 23.5 (95% CI: 12.3– 34.7) and 40.6 (95% CI: 25.8–55.4) respectively. We found an incidence rate of 2.2/year per 100,000 in the last 5 years. The sex ratio (females/ males) was 1.7. The mean age on prevalence day was 40.6 years (range: 15–76). The clinical course was relapsing-remitting in 82% of patients, progressive in 9% and secondary progressive in the other 9%. The mean EDSS score was 3.73 (range: 1–8.5). Our results confirm the hypothesis that Spain is an area at high risk for MS. Received: 7 May 1996 Received in revised form: 17 September 1996 Accepted: 23 September 1996