[Sleep and normality: usefulness for the practitioner].

About fifty percent of patients consulting their primary care physician complain of sleep disorders. Clinicians have to distinguish normal from abnormal sleep. For example, sleep normality is usually characterised by an apnea/hypopnea index < 5 h(-1) in absence of sleep symptoms. However such an index varies in relation with age, gender, body mass index, measurements methods In daily clinical practice, clinicians should look for sleep symptoms to define an abnormal sleep. More studies are needed to better define which patient will really benefit from a specific sleep therapy.