[Descriptive epidemiology of amyotrophic lateral sclerosis].

INTRODUCTION: ALS descriptive epidemiological information is wide, and is based on hospital registries, selective patients series and community studies of incidence, prevalence and mortality rates.

REVIEW: It has been revised studies found in the literature trying to analyse the methodology looking for approaches for a systematic review on the ALS descriptive epidemiology. The analysed works include on incidence, prevalence and mortality rates studies and we discuss possible biases and confounding factors.

CONCLUSIONS: Systematic review of ALS descriptive epidemiology should be based on the following criteria: community studies in non-selective geographic areas excluding aggregated cases zones, determination of crude prevalence rate and sex-age specific and standard population adjusted prevalence rates, presented with confidence intervals, selection of the cases should fulfil El Escorial criteria, sample size of source population greater than one hundred thousands in habitants, study period greater than five years and the dates should be accessible through Medline or other bibliographic sources.