The Glasgow Sleep Effort Scale: A reliability generalization meta-analysis of internal consistency

Objective The Glasgow Sleep Effort Scale (GSES) assesses the extent to which individuals engage in conscious, deliberate attempts to control their sleep. The present study aimed to conduct a reliability generalization meta-analysis to estimate the overall internal consistency of the GSES, to examine whether these estimates vary as a function of study and sample characteristics, and to assess the prevalence of reliability induction practices in the literature. Methods This systematic review and meta-analysis was preregistered on the Open Science Framework. A search was conducted in PubMed, Scopus, Web of Science, and PsycINFO from inception to November 12, 2025, using the term “Glasgow Sleep Effort Scale”. Two reviewers independently screened records using predefined eligibility criteria. Studies reporting Cronbach's alpha for the GSES total score were included. We conducted a random-effects meta-analysis using restricted maximum likelihood estimation. Results Thirty-four articles contributed 40 independent estimates (total N = 16,022). The pooled estimate was α = 0.81 (95% CI [0.79, 0.82]), indicating good overall internal consistency, although significant heterogeneity was observed ( I 2 ≈ 85%). Publication year significantly moderated internal consistency estimates, whereas language, mean age, sex, sample type, study design, and methodological quality did not. Reliability induction was observed in nearly 58% of the initially retrieved studies, most commonly due to the omission of reliability coefficients. Conclusion The GSES shows good internal consistency. Its frequent use underscores the need to report sample-specific reliability estimates.