Do you remember? Sleep fragmentation and immediate memory recall in sickle cell anaemia

Abstract

Introduction: A good night´s sleep can improve cognitive functioning the next day. An accumulation of disrupted sleep over time can impact on concentration and memory consolidation. Cognition is impaired over time in sickle cell anaemia (SCA) but mechanisms remain unclear. Sleep disturbances (e.g., sleep fragmentation, sleep disordered breathing) are common in SCA but there is little existing research examining any effect on cognition. Our objective was to compare sleep fragmentation and immediate memory recall in people with and without SCA. Materials and methods: Adolescents and young adults (AYA) of African heritage (Meanage= 21.20 [range 11-29.4 years], Ncontrol= 16 [4 male], NSCA= 17 [5 male]) were recruited from the community in London, UK. Sleep was measured with an Actiwatch for 7 days. Sleep data were collected with a sleep diary app developed for the study. Neuropsychological assessment from the Wechsler Scales of Intelligence and Memory for adults (i.e., WAIS IV & WMS IV) and children (i.e., WISC IV & CMS) was undertaken within 7 days of data collection. Data was analysed using hierarchical multiple regression to understand predictors of immediate memory recall in SCA. Results: Both groups slept on average 7 hours, but AYA with SCA experienced greater sleep fragmentation (SF; 32%) compared to controls (25%; p < 0.05) and had a non-significantly greater sleep latency of 47 minutes compared to 34 minutes in controls (p = 0.33). AYA with SCA experienced more mobile minutes during their sleep (M = 34.52,SD = 11.06) compared to controls (M = 45.70,SD = 14.12,p < 0.05) and less immobile bouts < =1min (M = 8.7,SD = 4.7) compared to controls (M = 14.18,SD =7.65,p < 0.05). The mean Full Scale IQ (FSIQ) and Immediate Memory Index (IMI) were lower in SCA compared to controls: FSIQSCA (M=4.6,SD= 11.4) and FSIQcontrols (M=107.13,SD= 9.92), and IMISCA (M=92.29,SD= 10.56) and IMIcontrols (M=102.64,SD= 9.11); p < 0.05 for both comparisons. Hierarchical multiple regression revealed that the full model of age, health status (i.e., with and without SCA), socioeconomic status (SES) and SF predicted IMI and was statistically significant, R2= 0.436, F (4, 26) = 5.03, p = 0.004, adjusted R2= 0.349. Conclusions: SES and sleep fragmentation appear to be contributing factors to the difficulties seen in immediate memory recall in AYA with SCA. Sleep fragmentation might be associated with sleep disordered breathing in SCA. It is not only important to understand what causes sleep fragmentation, but to develop interventions early on for people with SCA to reduce the risk of developing cognitive difficulties and to improve quality of life. Acknowledgements: Thanks to all participants for their time. This research was supported by the NIHR Great Ormond Street Hospital Biomedical Research Centre (GOSH BRC). The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health.