Incidence and Prevalence of Amyotrophic Lateral Sclerosis in Uruguay: a Population-based Study

Objective: To determine the incidence and prevalence of amyotrophic lateral sclerosis (ALS) in the Republic of Uruguay.

Methods: The study was performed in Uruguay (3,241,003 inhabitants) during a 2-year period (2002-2003). To ensure complete case ascertainment, multiple sources of information were used, including all the neurologists, other medical specialties, general physicians, neurophysiology laboratories, hospital medical records and death certificates. 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: Between January 1st, 2002, and December 31st, 2003, 89 new patients were diagnosed with probable or definite ALS. The mean annual incidence rate was 1.37 per 100,000 persons. The incidence was higher for men (1.95) than for women (0.84) with a male to female ratio of 2:1. For both, the incidence increased throughout the years showing a peak in the 65-74 age group among men and the 55-64 age group among women. Mean age at onset of ALS disease was 58.7 years. The estimated mean annual incidence for ALS calculated by the capture recapture method was 1.42 (95% CI, 1.13-1.72). On December 31st, 2002, the crude prevalence was 1.9 per 100,000 inhabitants.

Conclusions: ALS incidence is within a narrow range across countries despite the genetic, environmental and socioeconomic differences when similar prospective design, diagnosis criteria and data analyses are applied.