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Abstract Introduction It has been well-established that the rate of forgetting slows if learning is followed by a period of sleep versus wake. Although several studies compared rates of retention for material learned before sleep or sleep loss, none have explicitly examined how extended wake, without intervening sleep, impacts the rate at which information is forgotten. To explore this further, we investigated the effects of sleep deprivation on memory retention over extended wakefulness in dayshift (DS) versus nightshift (NS) participants. Methods N=22 adult shift workers (DS: n=17 and NS: n=5; aged 38.3±8.9 years; 12 females) participated in a 36-hr in-laboratory study. They adhered to their habitual wake time (DS: 5:50am; NS: 1:15pm) at home and arrived at the laboratory at 8:00am (DS)/8:00pm (NS). After a 2-hr acclimation period, participants followed a 24-hr constant routine protocol, which included continuous wakefulness. During the study, participants completed a memory task requiring the memorization of 20 nouns, ranging from 4-6 letters. The words were each individually presented on a computer screen for 10 sec. Recall sessions occurred immediately (session 1; 1+ hrs awake), 1 hr (session 2; 2+ hrs awake) and 24 hrs (session 3; 25+ hrs awake) post-memorization. The variable of interest is the proportion of words correct. Results A mixed-effects ANOVA, with fixed effects of session (1-3), shift (day vs. night), and their interaction, controlling for age, and a random intercept for participants, showed a significant main effect of session on the proportion of words correct (F2,38=36.65, p 0.001). Overall, the proportion of correctly recalled words decreased across sessions, with performance decreasing 12.5% from immediate to 1-hr, 18.8% from 1-hr to 24-hr, and 29.0% overall from immediate to 24-hr. Shift type and age did not significantly affect performance (p0.05). Conclusion The outcomes of this study replicated previous findings demonstrating the degradation of memory recall under the influence of sleep deprivation. The pattern of performance aligns with the conventional forgetting curve, in which forgetting occurs rapidly soon after learning, typically within the first hour, with the rate gradually decreasing over time. Future research will examine if continuous wakefulness exacerbated this memory decline. Support (if any) CARE Fund FY22-POP-02; HSSA; ARO W911NF2210223
Varghese et al. (Sat,) studied this question.