The Sleep Benefit in Episodic Memory: An Integrative Review and a Meta-Analysis

People recall more information after sleep than after an equally long period of wakefulness. This sleep benefit in episodic memory has been documented in almost a century of research. However, an integrative review of hypothesized underlying processes, a comprehensive quantification of the benefit, and a systematic investigation of potential moderators has been missing so far. Here, we address these issues by analyzing 823 effect sizes from 271 independent samples that were reported in 177 articles published between 1967 and 2019. Using multilevel meta-regressions with robust variance estimates, we found a moderate overall sleep benefit in episodic memory (g = 0.44). Moderator analyses revealed four important findings: First, the sleep benefit is larger when stimuli are studied multiple times instead of just once. Second, for word materials, the effect size depends on the retrieval procedure: It is largest in free recall, followed by cued recall and recognition tasks. Third, the sleep benefit is stronger in pre-post difference measures of retention than in delayed memory tests. Fourth, sleep benefits are larger for natural sleep and nighttime naps than foralternative sleep-study designs (e.g., SWS-deprived sleep, daytime naps). Although there was no obvious evidence for selective reporting, it is a potential threat to the validity of the results. When accounting for selective reporting bias, the overall effect of sleep on episodic memory is reduced but still significant (g = 0.28). We argue that our results support an integrative, multi-causal theoretical account of sleep-induced episodic memory benefits and provide guidance to increase their replicability.

Recognizing Atypical Dopa-Responsive Dystonia and Its Mimics

ABSTRACTPurpose of ReviewDopa-responsive dystonia (DRD) encompasses a group of phenotypically and genetically heterogeneous neurochemical disorders. Classic GTP cyclohydrolase 1 (GCH-1)-associated DRD consists of early-onset lower limb asymetrical dystonia, with sleep benefit, diurnal variation, and excellent and sustained response to low L-dopa doses.Recent findingsUnlike the classic phenotype, GCH-1-associated DRD may include features inconsistent with the original phenotype. We describe a GCH-1-associated late-onset DRD case with family history of parkinsonism and cervical dystonia whose response to levodopa was poor and complicated with dyskinesia, blepharospasm and severe non-motor symptoms. We use this case as a springboard to review the spectrum of atypical DRD, DRD-plus and DRD mimics.SummaryGCH-1-related dystonia may exhibit wide intrafamilial phenotypic variability, no diurnal fluctuation, poor response to L-dopa, and such complications as dyskinesia, epilepsy, sleep disorders, autonomic dysfunction, oculogyric crisis, myoclonus, or tics. More recently, rare GCH-1 variants have been found to be associated with Parkinson's disease. Clinicians should be aware of atypical DRD, DRD-plus and DRD mimics.

851 Self-Medication with Caffeine for 31 Years: A Case of Undiagnosed Childhood Narcolepsy Type II

Introduction Narcolepsy represents a relatively rare chronic neurological sleep disorder. While peak incidence occurs in adolescence and early-adulthood, reports indicate a substantial number of children under 10 remain undiagnosed or are misdiagnosed. The present case describes a female with undiagnosed narcolepsy type II self-medicating with caffeinated beverages from the age of 7. Report of case(s) A 40-year-old female presented at our clinic with excessive daytime fatigue and hypersomnolence despite adequate sleep (Epworth sleepiness scale= 16/24). The patient denied snoring, sleep paralysis, catalepsy, and hypnagogic/hypnopompic hallucinations. Symptoms began at the age of 7 and steadily worsened, with teachers reporting significant concentration difficulties and multiple episodes of unintentional sleep onset in the classroom. The patient reported heavily relying on caffeinated beverages from the age of 7 to remain awake and focused on classroom activities. Starting at the age of 7, the patient consumed on average a caffeine-equivalent of 1 espresso shot/day (64mg caffeine/day). This increased to 4–6 espresso shots/day (256-384mg caffeine/day) by the age of 12 and 5–9 espresso shots/day (320-576mg caffeine/day) by the age of 18. At the age of 25, the patient developed severe anxiety with panic attacks and episodes of suicidal ideation. With multiple episodes of sleep onset while operating a motor vehicle, a near-accident prompted medical evaluation. Diagnosed with general anxiety disorder and idiopathic hypersomnolence, escitalopram and armodafinil were started with limited effect. The patient continued self-medicating with caffeinated beverages until age 38 when she was diagnosed with narcolepsy type II. Sodium oxybate was subsequently added to her treatment plan with initial sleep benefit and caffeine reduction. A repeat mean sleep latency test confirmed narcolepsy type II (mean sleep latency= 3 minutes, mean rapid eye movement [REM] sleep latency= 3 minutes). Polysomnography was later performed due to non-resolving symptoms, revealing mild obstructive sleep apnea (REM apnea-hypopnea index= 13.5/hour). Continuous positive airway pressure was added to the treatment regime with significant sleep benefit. Conclusion We describe a case of undiagnosed childhood narcolepsy type II necessitating significant caffeine consumptions in order to maintain classroom performance. With known anxiety-provoking effects of caffeine, the case highlights the importance of addressing childhood narcolepsy. Support (if any):

046 Sleep-dependent prospective memory consolidation is impaired with aging

Introduction Existing literature suggests that sleep-dependent memory consolidation is impaired in older adults but may be preserved for personally relevant information. Prospective memory (PM) involves remembering to execute future intentions in a timely manner and has behavioural importance. As previous work suggests that N3 sleep is important for PM in young adults, we investigated if the role of N3 sleep in PM consolidation would be maintained in older adults. Methods 49 young adults (mean age±SD: 21.8±1.61 years) and 49 healthy older adults (mean age±SD: 65.7±6.30 years) were randomized into sleep and wake groups. After a semantic categorization task, participants encoded intentions comprising 4 related and 4 unrelated cue-action pairs. They were instructed to remember to perform these actions in response to cue words presented during a second semantic categorization task 12h later that encompassed either daytime wake (09:00-21:00) or overnight sleep with polysomnography (21:00-09:00). Results The significant condition x age group x relatedness interaction suggested that the sleep benefit on PM intentions varied according to age group and relatedness (p=0.01). For related intentions, sleep relative to wake benefitted young adults’ performance (p<0.001) but not older adults (p=0.30). For unrelated intentions, sleep did not improve PM for either age group. While post-encoding N3 was significantly associated with related intentions’ execution in young adults (r=0.43, p=0.02), this relationship was not found for older adults (r=-0.07, p=0.763). Conclusion The age-related impairment of sleep-dependent memory consolidation extends to prospective memory. Our findings add to an existing body of work suggesting that the link between sleep and memory is functionally weakened in older adulthood. Support (if any) This work was supported by the National Medical Research Council, Singapore (NMRC/STaR/015/2013) and the National Research Foundation, Singapore (NRF2016_SOL002).

Sleep-dependent prospective memory consolidation is impaired with aging

Study Objectives Existing literature suggests that sleep-dependent memory consolidation is impaired in older adults but may be preserved for personally relevant information. Prospective memory (PM) involves remembering to execute future intentions in a timely manner and has behavioural importance. As previous work suggests that N3 sleep is important for PM in young adults, we investigated if the role of N3 sleep in PM consolidation would be maintained in older adults. Methods 49 young adults (mean age±SD:21.8±1.61 years) and 49 healthy older adults (mean age±SD:65.7±6.30 years) were randomized into sleep and wake groups. After a semantic categorization task, participants encoded intentions comprising 4 related and 4 unrelated cue-action pairs. They were instructed to remember to perform these actions in response to cue words presented during a second semantic categorization task 12h later that encompassed either daytime wake (09:00-21:00) or overnight sleep with polysomnography (21:00-09:00). Results The significant condition x age group x relatedness interaction suggested that the sleep benefit on PM intentions varied according to age group and relatedness (p=0.01). For related intentions, sleep relative to wake benefitted young adults’ performance (p<0.001) but not older adults (p = 0.30). For unrelated intentions, sleep did not improve PM for either age group. While post-encoding N3 was significantly associated with related intentions’ execution in young adults (r=0.43, p=0.02), this relationship was not found for older adults (r=-0.07, p=0.763). Conclusions The age-related impairment of sleep-dependent memory consolidation extends to PM. Our findings add to an existing body of work suggesting that the link between sleep and memory is functionally weakened in older adulthood.

Influence of physical activity and sleep duration on the retinal and choroidal structure in diabetic patients: An SS-OCT study

ABSTRACTPurposeTo assess the association between physical activity, sleep duration, sitting time, and alterations of posterior segment structures with swept-source optical coherence tomography (SS-OCT).MethodsPatients with diabetic retinopathy (DR) were recruited, and diabetic patients without retinopathy (non-DR) who matched for age and duration of diabetes were used as control. The physical activity, siting time, and sleep duration were obtained by using standardized questionnaire. OCT parameters included: retinal nerve fibre layer (RNFL) thickness, ganglion cell inner plexiform layer (GC-IPL) thickness, retinal thickness, and choroidal thickness (CT). Linear regression was conducted to analyse the association.ResultsEach group included 116 diabetic patients. Average macular CT was positively correlated with metabolic equivalents (MET) only in the DR group, independent of age, gender, and other potential confounding factors (β = 1.163, P = 0.006). Average macular CT was also positively correlated with sleep duration only in the non-DR group, independent of age, gender, and other potential confounding factors (β = 10.54, P = 0.031). No correlation was found between MET, sleep duration, and other OCT parameters. Sitting time was not significantly correlated with OCT parameters either.ConclusionsPhysical activity and sleep duration are both positively correlated with macular choroidal thickness; this suggests that more time in physical activity and sleep benefit the retina, while there was no association between sedentary time and OCT parameters. Further studies are warranted to clarify the underlying mechanisms and the role of physical activity and sleep in CT alterations and DR.