Meta-analysis finds probiotics modestly improve sleep quality with low certainty

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Frontiers in Medicine Published May 23, 2026 Medically reviewed May 23, 2026 DOI ↗ By Dr. Ji-eun Park, MD · Brain, Mind & Pain

Key Takeaway

Consider probiotics as an adjunct for sleep quality, but recognize the evidence is low certainty with modest effects.

This meta-analysis pooled data from 39 randomized trials involving 4094 adults or adolescents to evaluate the effect of probiotic supplementation versus placebo on sleep disturbances. The primary outcome was the global Pittsburgh Sleep Quality Index (PSQI) score. Secondary outcomes included PSQI subdomains, insomnia severity, objective sleep measures, and OSA Sleep Inventory MA factors.

Probiotic supplementation was associated with a statistically significant improvement in global PSQI score (mean difference -0.71, 95% CI -1.23 to -0.20). Significant improvements were also seen in PSQI daytime dysfunction (MD -0.08, 95% CI -0.11 to -0.05), PSQI sleep time (MD 0.11, 95% CI 0.01 to 0.21), objective total sleep time (MD 13.82 minutes, 95% CI 1.15 to 26.49), and objective awake time during sleep period (MD -5.15 minutes, 95% CI -9.87 to -0.43). For insomnia severity, the overall effect was not significant (SMD 0.17, 95% CI -1.15 to 1.49), but a sensitivity analysis showed a significant reduction (SMD -0.44, 95% CI -0.74 to -0.14).

The authors note several important limitations: the certainty of evidence was very low for the PSQI global score and low for the insomnia severity sensitivity analysis. Effect sizes were modest, and clinical meaningfulness remains uncertain. Adverse events and tolerability were not reported.

In practice, probiotic supplementation may be associated with small improvements in subjective sleep quality, but clinicians should interpret these findings cautiously given the low certainty and modest effect sizes. Further high-quality trials are needed to confirm these results and establish clinical relevance.

Study Details

Study typeMeta analysis

EvidenceLevel 1

PublishedMay 2026

View Original Abstract ↓

IntroductionSleep disturbances are common and contribute to substantial functional and health-related burden. Probiotics have been proposed as a potential modulator of sleep via gut–brain axis mechanisms, yet the magnitude, consistency, and clinical significance of their effects remain uncertain. This study synthesized all randomized controlled trials evaluating the effect of probiotic supplementation on validated subjective and objective sleep outcomes, using harmonized change-score methodology and contemporary certainty-of-evidence grading.MethodsAn updated search (March 31, 2022–October 1, 2025) was performed in PubMed, Scopus, and Web of Science to identify randomized placebo-controlled trials evaluating probiotics in adults or adolescents. Outcomes included global Pittsburgh Sleep Quality Index (PSQI) scores, PSQI subdomains, insomnia severity, objective sleep measures, and OSA Sleep Inventory MA (OSA-MA) factors. Effect sizes were synthesized as mean differences or standardized mean differences comparing change from baseline between probiotic and placebo groups. Random-effects models were used for all analyses.ResultsThirty-nine trials (n=4094 participants) were included. Probiotic supplementation significantly improved PSQI global scores (mean difference (MD) –0.71; 95% CI –1.23 to –0.20; very low certainty). Benefits were domain-specific, with significant improvements in daytime dysfunction (MD –0.08; 95% CI –0.11 to –0.05) and sleep time (MD 0.11; 95% CI 0.01 to 0.21), while other subdomains showed no consistent effects. Insomnia severity did not improve overall (SMD 0.17; 95% CI –1.15 to 1.49), although sensitivity analysis excluding an influential study indicated a significant reduction (standardized mean difference (SMD) –0.44; 95% CI –0.74 to –0.14; low certainty). Objective sleep outcomes showed modest improvements, including increased total sleep time (MD 13.82 minutes; 95% CI 1.15 to 26.49) and reduced awake time during sleep period (MD 5.15 minutes; 95% CI 0.43 to 9.87). Probiotics significantly improved OSA-MA Factor 1 (sleepiness on rising; MD 1.07; 95% CI 0.40 to 1.75) and Factor 4 (refreshing on rising; MD 1.18; 95% CI 0.42 to 1.94), with no significant differences in other factors.ConclusionsProbiotic supplementation is associated with small improvements in global subjective sleep quality and selected subjective sleep domains. However, effect sizes are modest, certainty of evidence is generally low, and the clinical meaningfulness of these findings remains uncertain.Systematic review registrationhttps://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000057556, identifier UMIN000050539.