A vast literature review on the insomnia epidemiology, the most common sleep disorder, using MEDLINE and LILACS last 30 years of data, was performed from January 2002 to November 2003. The key-words were: sleep initiation disorders, sleep maintenance disorders, early awakening disorder, insomnia, sleep disorders, insomnia prevalence, insomnia consequences. Several insomnia definition criteria and epidemiology researches methods, with data comparison difficulties, were noticed. In the future it will be necessary similar insomnia definition and epidemiology studies criteria.
sleep; insomnia; epidemiology