Changing mortality patterns of motor neuron disease in Japan.

The age-adjusted female death rate from motor neuron disease in Japan was noted to rise after 1952 and to fall rapidly since about 1960. A similar trend was also noticed in the males. Further study will show whether this was a part of a cyclical change or whether the mortality of the disease has entered a period of prolonged decline in that country. Death rates for neurological diseases in various countries were reported previously for 1953-58. Updating this study for 1966-71, a rising trend of deaths from motor neuron disease was identified in European countries, but the rate has been stationary in the United States. The rapidly changing patterns of the mortality seemed incompatible with a purely genetic causation of the disease. This indicates the need for extensive epidemiological studies to identify the extrinsic factors which induced such a trend, and were thus possibly the cause of the disease. In view of the results of the re-evaluation of the diagnosis in death certificates, mortality figures of motor neuron disease in females appeared reasonably reliable for an epidemiological study.