MS Incidence Research Articles

Geographic variation of MS incidence in two prospective studies of US women.

To estimate the incidence of MS and its relation to latitude in two ongoing prospective studies of US women. A higher incidence of MS has been found in northern areas compared with southern areas of the United States and other countries, but the attenuation of this gradient in Europe in the last few decades and the consideration of ethnic factors have led some authors to question the existence of a strong association between MS and latitude. The authors identified new cases of MS among participants in the Nurses' Health Study (NHS), which took place between 1976 and 1994, and in the Nurses' Health Study II (NHS II), which took place between 1989 and 1995. The NHS included women born between 1920 and 1946, and the NHS II included women born between 1947 and 1964. The incidence of MS among NHS participants (181 definite/probable patients) increased significantly with latitude (p = 0.03, trend). Adjusted rate ratios were 3.5 (95% CI, 1.1, 11.3) for the north and 2.7 (95% CI, 0.8, 8.9) for the middle tiers relative to the southern tier. Among NHS II women (131 definite/probable patients), no association between latitude and MS was found (p = 0.89, trend). Adjusted rate ratios were 0.8 (95% CI, 0.4, 1.6) for the northern areas and 0.9 (95%, 0.4, 1.8) for the middle areas, relative to the southern areas. The association between latitude and risk of MS in the United States was corroborated, but there was an attenuation of the north-south gradient over time. If confirmed, this finding could provide new clues to identifying environmental causes of the disease.

Incidence of MS during two fifteen-year periods in the Gothenburg region of Sweden

The average annual incidence of definite and probable MS in Gothenburg was re-investigated. For 1950-1954, 1955-1959 and 1960-1964 it was 4.2, 4.2 and 4.3/100,000/year. For the five-year periods between 1974 and 1988 it was 3.0, 2.7 and 2.0/100,000/year. If possible MS was included, the corresponding incidence for 1950-1964 was 5.2, 5.3 and 5.1, and for 1974-1988 it was 3.9, 3.9 and 4.3/100,000/year. Neurological methods and diagnostic criteria were constant throughout the period. The 1950-1964 incidence was based on personally investigated cases, while the 1974-1988 incidence was based partly on review of Gothenburg neurology records. It is concluded that there has been a significant decrease in the incidence of MS in this area. However, the notified decrease may partly be explained by alterations in the case ascertainment procedure. Since the Swedish measles vaccination program started in 1971, the occurrence of measles has been declining and has practically ceased during the 1980s. The time when a possible influence of mass vaccinations against childhood diseases on MS incidence can be monitored is discussed.

Incidence of multiple sclerosis in the town of Sassari, Sardinia, 1965 to 1985: evidence for increasing occurrence of the disease.

Prevalence studies carried out in Sardinia from 1975 suggest an increasing occurrence of MS. However, it is questionable whether this increase represents a real change in MS incidence or simply reflects longer survival. Data from 79 patients indicated the average annual incidence for the period 1965 through 1985 was 3.4 per 100,000. On December 31, 1985, the prevalence rate was 69 per 100,000. Evaluation of MS temporal trends showed a significant increase in MS incidence during the study period: values ranged around two per 100,000 in the triennial periods 1965-1967, 1968-1970, and 1971-1973, and around five in each triennium from 1977 onward.

Epidemiology of multiple sclerosis in Bulgaria.

An epidemiological study of MS in 5 districts of Bulgaria was carried out over period of 10 years to establish MS prevalence, incidence and mortality. The district of Sofia was the highest, indicating increased prevalence among the urban population, and more female than male cases. In the age group up to 15 years, age at onset was significantly earlier in the urban than in the rural cases.

Declining incidence of multiple sclerosis in the Orkney Islands.

The incidence of MS in the Orkney Islands has been updated from 1941 to September 21, 1983. Since 1965, MS incidence rates have fallen significantly when compared with those for 1941 to 1964. Alterations in age-specific prevalence, mean duration of illness, and mean age of the MS population are consistent with the decline in incidence of MS in recent years. Although the reason for the decreasing incidence is uncertain, it is consistent with the hypothesis that MS may be caused by canine distemper virus.