Background/Objectives: Sleep is fundamental to physical and mental health, yet many individuals experience impaired sleep quality. Although pharmacological interventions are available, they are associated with risks of dependency and adverse effects, underscoring the urgent need for safer, food-based alternatives. Blueberry leaves, rich in hyperoside, are suggested to influence sleep through serotonergic and melatonergic pathways; however, while their potential to help maintain sleep quality has been noted, the sleep-enhancing effects of fermented blueberry leaf tea have not yet been demonstrated. This present randomized, double-blind, placebo-controlled trial evaluated the sleep-enhancing effects of fermented blueberry leaf tea on sleep quality. Methods: Fifty adults (aged 20–69 years) reporting poor sleep were randomly assigned to consume either fermented blueberry leaf tea (n = 25) or placebo tea (n = 25) three times daily for two weeks. Objective sleep parameters—sleep efficiency, wake after sleep onset (WASO), sleep latency, and total sleep time—were assessed using actigraphy, while subjective sleep quality was evaluated using the Oguri–Shirakawa–Azumi Sleep Inventory MA (OSA-MA) version questionnaire. Results: In the per-protocol analysis (active: n = 22; placebo: n = 20), the active group exhibited significant improvements in sleep efficiency and WASO compared with the placebo (p < 0.05). No significant differences were observed for sleep latency, total sleep time, or subjective assessments. Importantly, baseline sleep efficiency and WASO were negatively correlated with their respective improvements, suggesting that individuals with poorer initial sleep benefited most. Conclusions: These findings demonstrate that fermented blueberry leaf tea may enhance sleep continuity within two weeks, particularly among individuals with fragmented sleep, and support the potential role of functional foods in sleep health strategies. Trial registration: University Hospital Medical Information Network (UMIN), UMIN000055879; registered on 21 October 2024.
Shoji et al. (Fri,) studied this question.