Memory
Discrepant findings were observed across studies that investigated memory performance in children with SDB. These results were observed across a range of memory measures, such as the Children’s Memory Scale,20-21,37 California Verbal Learning Test,21,38 and NEPSY32 memory tasks.17,19,39-40 Children with SDB performed in the average range on working memory tasks.17,20 On verbal memory tasks, multiple studies indicated average encoding,17,21 consolidation,17,21short-term retrieval, 17,21 long-term retrieval,21 and recognition abilities17,21 across list learning21 and story learning tasks.17,21 Multiple studies suggested similarly average encoding, consolidation, short-term retrieval, and long-term retrieval abilities on visual memory tasks.17,20 Despite broadly average performance, some studies that included a control group reported differences in memory abilities for children with and without SDB.19,39-40 These differences were observed across verbal memory tasks,19 visual memory tasks,19 and tasks with both verbal and visual components.39-40 Kheirandish-Gozal et al39 measured non-verbal memory with four learning trials, an immediate recall trial, and a delayed recall trial and reported that children with SDB had lower overall performance on the first trial and over all four total trials compared to children without SDB. In addition, children with SDB had lower performance on the immediate and delayed recall trials compared to children without SDB.39 These results indicate that children with SDB may have difficulties with the acquisition and retention of new information. A more recent study supported these findings by reporting that children with OSA had poorer overall memory consolidation than controls on a spatial declarative memory task.40
Limited research has investigated differences of SDB severity level on memory performance. One study of SDB in school-aged children reported slight differences according to SDB severity; children who had mild SDB performed higher than children with moderate SDB on a narrative memory measure.16 Another study of SDB in overweight adolescents reported no differences among individuals with primary snoring, mild, or moderate SDB on verbal memory.21
To determine the impact of SDB on memory, multiple studies investigated associations between respiratory indices and memory performance. Gregory et al41 conducted an eight-year longitudinal study and reported that sleep problems at ages five, seven, and nine were not associated verbal memory performance at age 13. Kheirandish-Gozal et al39 reported that the respiratory arousal index predicted the slope of learning and delayed recall in children with SDB. These results indicated that sleep fragmentation may influence the challenges that children with SDB have when selecting efficient learning strategies.39 A more recent study identified specific sleep architecture features associated with NREM stage two sleep in SDB that might influence memory consolidation.40 In healthy children, sleep-dependent memory consolidation is associated with NREM stage two (N2) sleep spindles. N2 sigma power is positively associated with memory consolidation.40 In this study, children with OSA had lower N2 sigma power than children with PS and controls.40 Therefore, N2 sigma power might serve as a biomarker of neurocognitive challenges in pediatric SDB.
The literature reviewed above revealed multiple discrepancies regarding memory performance in children with SDB. A number of the studies were limited by small sample sizes.40 In addition, most of these studies defined SDB and SDB severity with different criteria, making it challenging to compare results across studies. While some of these studies recruited participants from the general population,17,19 others included clinical samples of children referred for concerns regarding SBD,16,20,39-40 which may create potential referral bias.