Thursday, January 02, 2003
By Health Newswire reporters
Experts who have discovered large regional differences in the incidence of multiple sclerosis (MS) in Finland say that these findings point to locally acting environmental factors.
Several studies have shown that Finland is a high-risk region for MS, with a prevalence of 100–200 per 100,000 for different areas of the country. The prevalence of MS in the western district of Seinajoki, for example, is twice as high as in the western region of Vaasa and southern Uusimaa.
Dr Marja-Liisa Sumelahti and colleagues from the University of Tampere and the University of Helsinki Hospital used hospital records to identify new cases of MS in Uusimaa, Vaasa and Seinajoki between 1979 and 1993.
MS cases were classified into relapsing-remitting (RRMS) and primary progressive MS (PPMS) subtypes in order to determine whether aetiological differences between the two forms of the disease might exist.
The team found that during the period 1979–1993 the age-adjusted incidence of MS was 5.1 per 100,000 person-years in Uusimaa, 5.2 in Vaasa and 11.6 in Seinajoki. The rates of MS in Uusimaa over this time remained stable, whereas a decrease occurred in Vaasa and an increase in Seinajoki.
In addition, parallel incidence trends for RRMS and PPMS were found in all three districts, suggesting that there are similar environmental triggers for both clinical types of MS, the researchers said.
Dr Sumelahti’s team speculate that since genetic change in populations is slow, recent changes in environmental factors were most likely to be responsible for the sharply diverging incidence trends.
“The environmental causes are generally suspected to be of viral origin but remain largely unknown at present,” they add.
Reference: Sumelahti et al, Journal of Neurology, Neurosurgery &
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