**10. Conclusions**

Despite the time elapsed since its initial description, UARS remains controversial as it has yet to be accepted as its own entity. However, the literature continues to reflect interest in this disorder. Perhaps SAHS and UARS share the same pathophysiological mechanism, although their clinical expression and pathophysiologic consequences are different. We could say that UARS and OSAS are distinct entities in the spectrum of sleep-disordered breathing.

SAHS is one of the most common sleep disorders in clinical practice. It is associated to cardiovascular morbidity, and has become regarded as a public health problem. UARS is an underdiagnosed disorder with low prevalence of sleep units. It has special implications on sleep structure, especially sleepiness and tiredness, and is associated to chronic somatic diseases such as chronic fatigue syndrome, fibromialgia, irritable bowel syndrome, and tension headache. The correct diagnosis of this syndrome is essential to allow the best choice of therapy.

The identification of UARS, although not recognized by the AAMS as an entity, has improved our understanding of respiratory events and arousals, as well as increasing the search for non-invasively ways of assessing respiratory effort. Today, terms such as airflow limitation or RERAs are widely used in the polysomnographic reports.
