Mortality statistics for multiple sclerosis and amyotrophic lateral sclerosis in Sweden

Background: Multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS) are chronic neurologic diseases for which distinct explanations of the pathogenesis are lacking. Two large Swedish register studies have rather unexpectedly detected a correlation between MS and ALS. The aim of this study was to investigate if an association between ALS and MS could be demonstrated as has been shown earlier.

Material and methods: Data on mortality from ALS and MS, 1990-2010, were collected from the Swedish National Statistics Office. In all there were 5,696 deaths due to ALS and 3,941 deaths due to MS. Age- and sex-adjusted mortality rates were calculated.

Results: There was no correlation between the mortality rates of ALS and MS in the 21 counties of Sweden for the period 1990-2010 (Spearman's rho = -0.052; p = 0.822; n = 21). The national mean mortality rate for ALS throughout the period of 1990-2010 was 2.98 per 100,000 person-years (95% CI 2.87-3.08). For MS the national mean mortality rate was 2.04 per 100,000 person-years (95% CI 1.95-2.12).

Conclusion: This study did not confirm the previously shown association between MS and ALS in Sweden.