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western hospital districts of Vaasa, South Ostrobothnia and Pirkanmaa were calculated in 1980-2007 by using previously unpublished data obtained from a retrospective search from hospital administrative registries.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.

Neurological comorbidity and survival in multiple sclerosis.

OBJECTIVE: There is increasing interest in the survival of multiple sclerosis (MS). MS itself may decrease life expectancy; however, several other comorbid diseases may also influence survival. We aimed to evaluate frequency of other neurological conditions and survival in the population-based Finnish Northern Ostrobothnia MS cohort. METHODS: The frequencies of neurological comorbid diseases and their associations with gender, clinical course, disability level (EDSS) and duration of MS were evaluated in population based cohort of 491 patients with clinically definite MS that was diagnosed between 1990 and 2010. The survival rate of the patients was also analysed. RESULTS: One or more neurological comorbid disease was present in 17.1% of patients (n=84). The prevalence of epilepsy in MS patients was 4.7%, which is greater than that in the general population. Migraine was significantly more common in women with a benign MS course when compared to other types of MS (p=0.046). A significant association between peripheral nervous system disorders and primary progressive MS was found (p=0.027). The 21-year survival rate from time of diagnosis was 90.5%. Stroke decreased the 21-year survival rate of the patients (p=0.003). An association between stroke prevalence and the duration of MS disease was also detected (p=0.023). CONCLUSIONS: This is the first report of multifaceted neurological comorbidities in MS patients. Neurological comorbidity is rather common in MS. However, only the prevalence of epilepsy was increased in MS patients compared to the general population. An association between peripheral nervous system disorders and primary progressive MS was also found. The 21-year survival rate was greater in the present population based cohort compared in other studies, but stroke seems to decrease the survival rate in MS patients.