Efficacy and Safety of Bacillus coagulans IDCC 1201 for Sleep Improvement in Adults with Sleep Disturbance: A Randomized, Double-Blind, Placebo-Controlled Polysomnographic Study

Background/Objectives: Sleep continuity is a key determinant of daytime functioning; however, accessible and well-tolerated interventions remain limited. We investigated whether Bacillus coagulans IDCC 1201 improves objective sleep continuity and subjective sleep quality in adults with sleep disturbance. Methods: In this 4-week, randomized, double-blind, placebo-controlled trial, 80 adults (aged 19–65 years) received B. coagulans IDCC 1201 (5.0 × 109 CFU/day) or a placebo; 78 participants completed the study. The primary endpoint was the change in polysomnography-derived sleep efficiency from baseline to week 4. Results: Compared with the placebo, B. coagulans IDCC 1201 significantly improved sleep efficiency (Δ +13.71 ± 21.14 vs. −0.15 ± 13.35%; p = 0.002) and increased sleep duration (total sleep time: Δ +49.56 ± 76.33 vs. −0.50 ± 48.02 min; p = 0.002), accompanied by reduced nocturnal wakefulness (wake after sleep onset: Δ −44.40 ± 72.32 vs. +1.88 ± 44.36 min; p = 0.003; and total wake time: Δ −12.28 ± 20.22 vs. +0.53 ± 12.32 min; p = 0.004). Sleep-stage distribution also favored B. coagulans IDCC 1201, with greater increases in stage 2 and REM duration compared with the placebo (between-group p = 0.008 and 0.032, respectively). Subjective sleep quality showed greater improvement with B. coagulans IDCC 1201 (Pittsburgh Sleep Quality Index change: Δ −3.67 ± 3.37 vs. −1.64 ± 2.83; p = 0.036), yielding lower week 4 scores (5.87 ± 2.26 vs. 8.28 ± 3.62; p = 0.001). No significant safety concerns were identified. Conclusions: These findings indicate that strain-defined probiotic could be used as a nutritional approach for sleep health, particularly for targeting sleep fragmentation and maintenance.