Sleep Apnea Effects on Memory: Consequences and Mechanisms
2015 ABSM Junior Faculty Research Grant
Andrew Varga, MD, PhD
Icahn School of Medicine at Mount Sinai
Key Project Outcomes
OSA occurs when the muscles and tissues surrounding the upper airway collapse partially or completely during sleep, resulting in a period where breathing stops or is significantly attenuated before the airway opens again. This phenomenon occurs repeatedly during sleep; in individuals with severe OSA, it can occur nearly every minute or more. OSA is thought to have at least 2 main consequences: 1) levels of oxygen in the blood go down, and then go up again when the airway reopens. This is called intermittent hypoxia (IH). 2) when the airway reopens, a small arousal occurs. Although this arousal may go unnoticed by the individual, it nonetheless fragments sleep and can make some people sleepy the following day, even if the total sleep duration is long. Sleep architecture is broadly divided into non-REM and REM stages. OSA can occur in either non-REM or REM sleep, but because these stages of sleep are very different, it is possible there are may be differential effects of OSA in either stage.
This project investigated whether OSA limited to non-REM sleep was deleterious to the processing of spatial navigational memory. Our preliminary data suggest that the benefit of normally consolidated sleep on spatial navigational memory is reduced with OSA is introduced in non-REM sleep, without a significant impact on attention during a psychomotor vigilance test.
This project also set out to evaluate potential differences in the effect of OSA when OSA either did or did not contain intermittent hypoxia. We developed a novel paradigm in which to assess this, by withdrawing CPAP therapy for OSA either with or without supplemental oxygen. Our preliminary data suggest that we can create a unique form of OSA which is primarily composed of sleep fragmentation and in which the intermittent hypoxia is significantly limited. Using this model, our preliminary data further suggest that either form of OSA results in reduced spatial navigational memory versus normally consolidated sleep. This suggests that while intermittent hypoxia may be detrimental, sleep fragmentation from OSA alone is sufficient to negatively impact spatial navigational memory.