Incidence of ALS in Italy: evidence for a uniform frequency in Western countries

Objective: To determine the incidence of ALS in two regions of Northwestern Italy, utilizing a prospective design. Methods: The study was performed in Piemonte and Valle d'Aosta (4,418,503 inhabitants) during the period 1995 to 1996. All neurologic departments in the two regions were involved in the study and prospectively collected and followed up ALS cases. Other secondary sources of information were used in order to ensure complete case ascertainment. ALS diagnosis was based on El Escorial criteria. Although all patients with motor neuron disease were enrolled in the follow-up, only probable and definite cases are included in the study. Results: During the study period, 221 cases of ALS were found (120 men and 101 women), corresponding to a mean annual crude incidence rate of 2.5/100,000 population (95% CI 2.2 to 2.9). The rate was higher for men (2.9) than for women (2.3), and increased with age to a peak in the 75 to 79 age group among men and to the 70 to 74 age group among women. Conclusions: Comparing these data to those of epidemiologic studies with a similar prospective design, the incidence rates are similar, despite the large differences in terms of genetics, environment, and socioeconomic background. This finding points to diffuse environmental or genetic factors rather than to a specific exogenous toxin in the pathogenesis of ALS.