Endemic in Western societies (~18–23%), sleep disorders are often co-morbid and rank as a major risk factor for psychiatric, cerebro-cardiovascular, metabolic or hormonal diseases [1]. They also aggravate everyday's life, often to a relevant extent. Subjects with sleep disorders complain of excessive daytime drowsiness, impaired cognition, mood changes, anxiety, fatigue, or reduced tolerance to pain more often than good sleepers [2]. They seek medical assistance or anticipate retirement more frequently and use more prescribed medication according to surveys and population-based studies [3].
