Motor neuron disease in the Province of Turin, Italy, 1971-1980.

The incidence and prevalence of motor neuron disease (MND) in the Province of Turin, North-West Italy, were investigated for the period 1971-1980. The crude incidence rate of MND was 0.67/100,000/year. The annual incidence rate, age and sex adjusted to the Italian population in 1971 was 0.69 cases per 100,000 inhabitants, 0.94 for men and 0.45 for women, with a male to female incidence ratio of 2.09:1. The prevalence of MND was 2.62/100,000, 3.57 for males and 1.71 for females. The mean age at the time of diagnosis was 55.6 years. Annual incidence rates increased with advancing age. Amyotrophic lateral sclerosis was found to be 4 times more frequent than progressive muscular atrophy (0.53/100,000/year v. 0.14/100,000/year). The distribution of MND was uneven in the Province suggesting a proportional relationship to the distribution of population density. Possible explanations of this finding are discussed.