The epidemiology of multiple sclerosis and tuberculosis in Finland. A study based on mortality statistics.

Mortality statistics were used to check the previously observed uneven geographical distribution of multiple sclerosis (MS) in Finland, and also to compare the distribution of tuberculosis and MS with each other. In total, 331 MS deaths which could be regarded as deaths primarily due to MS were registered during the period from 1963 to 1971. The mean age at death was 49.9 years. The mean annual mortality rate was 0.8 per 100,000 population. The highest rates due to MS were registered in the western county of Vaasa. The cumulative mortality and birth rates showed a significant accumulation of MS cases to the western county of Vaasa and the southwestern county of Turku and Pori. A previous study revealed a high percentage of familial cases of first-degree kinship in the selected district of Jalasjärvi in the county of Vaasa. The mortality material revealed one additional MS case which raised the familial percentage to 13 among the living patients in this district. Statistics of tuberculosis have shown a constant accumulation of the disease in the western part of the country for more than 100 years. The mean annual mortality rate for tuberculosis was 17.1. The highest rate (23.0) was found in the western county of Vaasa, where the mortality rate (1.34) for MS was highest. Previous immigrant studies in Finland suggest that the uneven geographical distribution of tuberculosis is due to hereditary factors. The population of Finland consists of varying degrees of isolates, and the similarity of the distributions of MS and tuberculosis may thus reflect a common genetic factor in their aetiology.