Temporal and geographic variation in United States motor neuron disease mortality, 1969-1998

Objective: To describe temporal trends of motor neuron disease (MND) mortality in the United States. Variations in MND by demographic variables of sex, age, geography, and race/ethnicity were evaluated to assess the possible explanations for observed trends. Methods: Multiple-cause mortality files from the National Center for Health Statistics for the years 1969 through 1998 were searched for all United States death records with codes corresponding to MND. Age-adjusted mortality rates were calculated by sex, race/ethnicity, age, birth cohort, and place of death. Results: Overall MND mortality rates increased from 1.25 per 100,000 to 1.82 per 100,000, representing a 46% increase during the 30-year period. Rates among women increased by 60% and continue to rise. Rates among men rose by 35% during this period but have leveled off in the most recent decade evaluated. Mortality rates among African Americans and Hispanics were approximately 50% lower than rates among non-Hispanic whites. A southeast to northwest gradient was observed when rates were grouped by 12 geographic areas. MND mortality rates per 100,000 (and 95% CI) ranged from 2.22 (1.89 to 2.55) in the Northwest to 1.57 (1.44 to 1.71) in the Southeast. Conclusions: Variations in motor neuron disease ( MND) mortality by time, race/ethnicity, sex, and geography were consistent with the hypothesis that environmental exposures, combined with factors of genetic susceptibility, play a role in the development of MND.