Effects of auditory sensory stimulation on consciousness and physiological parameters among individuals with disorders of consciousness: a systematic review and meta-analysis

Objective To systematically evaluate the effects of auditory sensory stimulation (SS) on consciousness levels and physiological parameters in patients with disorders of consciousness (DOC). Furthermore, this study aimed to explore intervention characteristics based on the frequency, intensity, time, and type (FITT) framework that may influence treatment effects and to investigate potential sources of between-study heterogeneity. Methods This systematic review and meta-analysis was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The PubMed, Embase, Cochrane Library, Web of Science, Scopus, and ProQuest databases were systematically searched from database inception to April 25, 2026. Fifteen randomized controlled trials involving 713 patients with DOC were included. Meta-analyses were performed using postintervention endpoint data (means, standard deviations, and sample sizes), and effect sizes are expressed as the mean differences (MDs) with 95% confidence intervals (CIs). Subgroup analyses based on the FITT framework, univariable random-effects meta-regression analyses, and GRADE assessments were conducted to explore potential sources of heterogeneity and evaluate the certainty of evidence. Results Auditory SS was associated with higher postintervention Glasgow Coma Scale (GCS) scores and a lower postintervention pulse rate than control conditions. No statistically significant between-group differences were detected in systolic blood pressure, diastolic blood pressure, respiratory rate, oxygen saturation, or body temperature. Exploratory FITT-based subgroup analyses showed numerical differences in effect estimates across some intervention categories, but these findings did not establish an optimal intervention protocol. Univariable meta-regression analyses identified no statistically significant study-level moderators. According to the GRADE assessment, the certainty of evidence was low for GCS scores and very low for all physiological outcomes. Conclusion Auditory SS may have potential as an adjunctive rehabilitation intervention for patients with DOC, although confidence in its effect on GCS scores is limited by the low certainty of evidence. Its effects on physiological outcomes remain highly uncertain. The available evidence is insufficient to establish an optimal FITT-based protocol. Future high-quality randomized controlled trials using standardized auditory SS protocols, comprehensive reporting of stimulation parameters (particularly stimulation intensity), and consistent outcome measures are needed to establish the optimal FITT prescription for auditory SS.