Neurocognitive Deficits in Patients with Obstructive Sleep Apnea Syndrome (OSAS)

Obstructive Sleep Apnea Syndrome (OSAS) is a common sleep-related breathing disorder affecting 5% of the general population (Young et al., 2002). OSAS is characterized by periodic complete or partial cessation of breathing while sleeping. These recurrent events of breathing result in fragmented sleep and recurrent hypoxemia (reductions in hemoglobin oxygen levels) (American Academy of Sleep Medicine, 1999). It has been documented that OSAS causes excessive daytime sleepiness, mood changes and dysfunctions in several cognitive domains (Engleman & Joffe, 1999; Tsara et al., 2009). However, there are different opinions on which cognitive abilities are affected mostly by OSAS and on the exact nature of cognitive decline. The comparison of the findings of research studies is difficult because of differences in severity of disease, criteria that are used to assess the severity of syndromes and different sample sizes (Quan et al., 2006). Other variables such as the sensitivity of neuropsychological battery chosen (Quan et al., 2006) and different group ages are also confounding factors (Mathieu et al., 2008). Nevertheless, in this chapter an effort is made to review studies which examined neurocognitive deficits in OSAS as well as those which reported the Continuous Positive Pressure Therapy (CPAP) treatment effects on several cognitive domains found to be impaired in OSAS. In addition, the most frequent explanations concerning the mechanism of neurocognitive deficits in OSAS patients and the neuroanatomical pathophysiology of OSAS are discussed.