Increasing mortality from amyotrophic lateral sclerosis in Norway?

OBJECTIVE: To investigate a possible increase in incidence of ALS in Norway. METHODS: Death certificate data from all deaths in Norway in the period 1961 to 1994 for ALS, PD, and MG were obtained from Statistics Norway and related to population statistics. Data on ALS was obtained on sex, age, and place of death and compared with mortality data in PD and MG for the same period. Data were standardized using the 1990 population as standard population. Poisson regression was used to test for trends in mortality. The data from the death certificates were related to a clinical study performed on ALS in one of the counties during the same period. RESULTS: The annual mortality of ALS almost doubled during the period studied, rising from 1.38 to 2.54 per 100,000 inhabitants at the end of the study. The increased mortality appeared solely in the population older than 60 years of age, with a peak in mortality in the age group 80 to 84 years. The increase was larger in women than in men, and the ratio between the sexes was 1.32 (men-women, age-adjusted at the end of the study). The mortality in patients with PD showed a similar increase to that seen in ALS, whereas no increase in mortality was observed in patients with a diagnosis of MG. There were considerable differences in ALS mortality in different counties, but no clear regional trends were observed. CONCLUSION: The authors report increasing ALS mortality. Although the increase in mortality is restricted to the population aged 65 years or older, it cannot be explained by increasing age of the general population alone.