Incidence of amyotrophic lateral sclerosis in Costa Rica

Abstract

Objective. Amyotrophic lateral sclerosis is a degenerative disease of the central nervous system that is characterized by progressive affection of the upper and lower motor neuron. Until now, there has not been a publication that refers to its incidence in our country. The present investigation is based on the analysis of patients seen with the diagnosis of this illness from January 1998 to November 2001.

Methods. Incidence rate per person-years was calculated and variables such as sex, age of diagnosis, ethnics, geographic distribution, classifi cation of the disease, treatment and diagnostic methods were analyzed.

Results. Between January 1998 and December 2001 a total of 102 cases were diagnosed with ALS in Costa Rica, the annual incidence rate 0.97 (I.C. 95 % 0.8 a 1.2) per 100.000 person-years. 76 medical records were reviewed. Twenty eight were females and forty eight males, the M: F ratio was 1.7. The average age of diagnosis was 58.4 years for females and 53.1 years for males (p = 0.15). The geographic distribution showed that 75% of the patients live in San José, Alajuela and Cartago, with a very similar incidence rate. The incidence increases with age in women, while in men shows a peek of onset at the sixth decade.

Conclusion. The study shows that the incidence of ALS in our country appears to be similar to those countries with lower rates of incidence. The incidence rate was stable in the years of the study; the disease affects more men than women.