The role of melatonin timing on short-term memory retention during sleep restriction

RATIONALE: Acute sleep restriction is a prevalent issue among young adults, significantly impairing cognitive functions, particularly short-term memory. Melatonin, known for its role in circadian rhythm regulation and neuroprotection, presents a promising intervention for mitigating these deficits. OBJECTIVES: This study aimed to determine the effect of timed melatonin administration on short-term memory retention in young adults (aged 18–23) undergoing acute sleep restriction. We hypothesized that melatonin would mitigate the decline in memory retention and exert a significant, independent effect. METHODS: A randomized, double-blind, placebo-controlled design was employed over three days, involving 60 healthy university-aged individuals (30 per group). Participants received either 3 mg melatonin or an identical placebo 30 min before bedtime on two nights of sleep restriction. Short-term memory was assessed at baseline and post-intervention using the California Verbal Learning Test (CVLT), with adjusted memory retention percentage as the primary outcome. Cognitive ability (WAIS-IV Digit Span) and subjective sleep quality (Pittsburgh Sleep Quality Index) were also measured. Statistical analysis included paired and independent t-tests, and multivariate regression. RESULTS: Both groups were well-matched at baseline in memory score (p = 0.770), cognitive ability (p = 0.083), and sleep quality (p = 0.708). The placebo group showed a significant decline in memory score from baseline (mean ± standard deviation: 84.06 ± 4.50) to post-intervention (69.00 ± 6.74; t(29) = 16.62,p < 0.001,Cohen′sd = − 3.04). While the melatonin group also experienced a reduction (baseline: 84.40 ± 4.66; post-intervention: 77.48 ± 5.41; t(29) = 10.44,p < 0.001,Cohen′sd = − 1.91), their adjusted memory retention was significantly higher (mean ± standard deviation: 92.19% ± 3.89%) compared to the placebo group (82.00% ± 6.22%; t(58) = 7.60,p < 0.001,Cohen′sd = 1.96). Multivariate regression confirmed that group assignment (melatonin vs. placebo) was a significant predictor of adjusted memory retention (β = 10.35,p < 0.001), while cognitive ability (p = 0.772) and subjective sleep quality (p = 0.293) were not. CONCLUSIONS: Timed melatonin administration effectively mitigated the decline in short-term memory retention during acute sleep restriction in young adults. These findings support the use of melatonin as a potential countermeasure for cognitive deficits associated with sleep deprivation, demonstrating a significant independent effect.