Incidence of ALS in Lombardy, Italy.

Objective: To assess the incidence and trends of ALS in a large population at risk.

Methods: This study was performed in nine provinces of Lombardy in Northern Italy (population 4,947,554). Patients with newly diagnosed ALS were enrolled during the period 1998 to 2002 through a prospective regional register. For each patient, the main demographic and clinical information was collected by the caring physicians and reviewed by a panel of experts according to the original and revised El Escorial diagnostic criteria. Overall, age- and sex-specific and standardized annual incidence rates were calculated for the entire population and for each year and province separately.

Results: We studied 517 patients (M:F ratio 1.3) aged 18 to 92 years (mean 63.6). Onset of symptoms was bulbar in 29% of cases. ALS was definite in 45%, probable in 27%, probable laboratory supported in 3.5%, possible in 15%, and suspected in 10%. Mean disease duration at diagnosis was 10.6 months. The standardized incidence rate was 2.09 per 100,000/year (95% CI: 1.17 to 3.18). The rate, which was 2.43 in men and 1.76 in women, tended to increase up to ages 65 to 74 and to decrease thereafter. The rate was unchanged over time and presented moderate variations across provinces. The incidence rate of definite ALS was 0.93 (spinal-onset ALS 1.35; bulbar-onset ALS 0.74) and was consistently higher in men with spinal-onset ALS vs men with bulbar-onset ALS and women.

Conclusions: The incidence of ALS varied according to age, sex, and site of onset. No temporal and geographic clusters were detected over a 5-year period.