The Effect of Continuous Positive Airway Pressure (CPAP)
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Obstructive sleep apnea (OSA) is a clinical sleep disorder that is characterized by frequent pauses in breathing during sleep due to obstructions of the upper airway, and can lead to a range of cardiovascular and neuropsychological deficits, including memory problems. During sleep, recent memories are actively processed and consolidated into pre-existing knowledge networks. Consolidation is also discriminatory, such that memories that are relevant for future behavior are enhanced more so than other memories. It is possible that the memory deficits associated with untreated OSA are due to deficits in memory consolidation from disrupted sleep. Continuous positive airway pressure (CPAP) is the standard treatment for OSA, and long-term use has been shown to ameliorate the physiological, psychological, and memory impairments associated with OSA. This study investigated the effect of a single night of CPAP treatment on memory consolidation. The study included treatment-naïve OSA patients (no-CPAP group) and OSA patients receiving their first night of CPAP treatment (CPAP group). All participants completed two consecutive rounds of study followed by a test for picture- location memories from two categories of objects before a sleep period. In addition, just prior to sleep, all participants were informed that they would complete the memory test again in the morning and if their memory for one specific category of objects improved from the evening test they would receive additional compensation. Before the morning test, all participants were informed that, counter to the previous instruction, they would receive the monetary bonus upon improvement in both reward-relevant and reward – irrelevant object categories. There were no differences in memory accuracy or in memory change from the evening to the morning test between groups. Furthermore, both groups showed better retention of reward-irrelevant compared with reward-relevant items from the evening to the morning test. These results suggest that a single night of CPAP use is not sufficient to improve memory. Furthermore, while both groups became less confident in their responses from the evening to the morning test, the no-CPAP group showed a greater confidence decrease for reward-irrelevant compared with reward-relevant items. This suggests that memory consolidation processes may have actually been more efficient for the no-CPAP group compared with the CPAP group, perhaps due to the difficulty adjusting to initial CPAP use. Overall, these results suggest that future research including objective sleep measures is necessary to fully understand the relationship between OSA, CPAP, and memory consolidation.