Why an issue on sleep apnea? A simple answer is that sleep apnea is now known to be associated with increased mortality rates, especially in younger patients. As physicians, we need to be aware of the condition, be able to identify individuals at risk, be able to perform reliable diagnosis with methods that are within reach in terms of both practicality and cost, and be able to give all patients a chance of treatment, especially those of low socioeconomic status. However, the role of obstructive sleep apnea (OSA) in determining comorbidities or excess deaths has been disputed in the past [1]. Many recent studies, performed on clinical and general population samples, have demonstrated an excess of deaths in patients with moderate to severe sleep apnea, especially in the younger cohorts (usually <60 years old) [2-4].
The term "new epidemic" is appropriate because recent epidemiological studies demonstrated that about one quarter of the general population older than 30 years suffers from sleep-disordered breathing (SDB), and that in 2% of females and 4% of males the presence of SDB and clinical symptoms has been found. Of course, this new epidemic could be attributed to the "obesity pandemic", as excess weight is the strongest contributing factor for the development of sleep apnea. However, it was recently demonstrated that only 40-50% of sleep apnea incidence could be attributed to excess weight.
Sleep apnea has many pathological consequences, including cardiovascular disease, sleep fragmentation, reduction in quality of life, daytime sleepiness, increased risk for motor vehicle accidents, and, finally, chronic respiratory failure with cor pulmonale, especially in patients with other respiratory comorbidities.
The diagnosis of OSA requires a clinical assessment and an overnight sleep study. Full-standard laboratory polysomnography has long been considered the only tool to diagnose sleep apnea, but it is expensive, requiring highly trained personnel and sophisticated equipment, too. Therefore, sleep laboratories have long waiting lists for in-lab polysomongraphy, resulting in delays to diagnosis and treatment. Fortunately, different diagnostic tools are now available for patients with a high probability of OSA, based on clinical assessment associated with the use of portable monitors such as portable polysomnography, cardiorespiratory monitoring or devices for photoplethysmographic or pulse-transit-time recording [5].
Continuous positive airway pressure (CPAP)-treated patients compliant with treatment had mortality rates similar to those recorded in the general population, and the major determinant of long-term outcome was compliance with CPAP treatment rather than severity of OSA at diagnosis [6]. These data stress that great effort should be expended to achieve early diagnosis of this condition, thus affording effective treatment.
However, the new protocol proposed for the identification of respiratory events during sleep may result in a lower sensitivity. The new definition of hypopnea—any discernible reduction of airflow associated with a desaturation of >4% [7]—and the use of portable monitors result in an underestimation of the number of identified respiratory events. As a result of this bias, the apnea-hypopnea index is also underestimated in patients with relevant symptoms, leading to delays in starting adequate therapy [8,9].
In conclusion, this new issue summarizes the latest findings on the epidemiology of OSA as well as developments in screening tools and therapeutic strategies that may help clinicians in their diagnosis and treatment of this important sleep disorder.

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