Systematic Review and Meta-Analysis: Prevalence of Meibomian Gland Dysfunction Among Adults Aged 40 Years and Older

Background: Meibomian gland dysfunction (MGD) is a major contributor to evaporative dry eye disease, yet reported prevalence estimates vary widely across studies, largely due to differences in diagnostic criteria, study populations, and settings. We conducted a systematic review and meta-analysis to synthesize available evidence on the prevalence of MGD in adults aged ≥40 years and to examine sources of heterogeneity across studies. Methods: We systematically searched PubMed, Web of Science, Scopus, and Google Scholar from inception to November 2025 for observational studies reporting the prevalence of MGD in adult populations. Random-effects meta-analysis of proportions was performed. Subgroup analyses were conducted by study setting and diagnostic approach. Between-study heterogeneity was quantified using the I² statistic. Results: Eight observational studies from Singapore, Spain, Russia, Iran, China, Japan, and New Zealand, comprising 20,518 participants, met inclusion criteria. Reported prevalence of MGD varied substantially across studies. The pooled prevalence estimate was 87.08% (95% CI: 65.32-96.02%); however, heterogeneity was extreme (I² > 99%), indicating substantial variability across populations and study methods. This pooled estimate should be interpreted with caution and not as a single representative global prevalence. Studies using clinical signs alone tended to report higher prevalence than those incorporating both signs and symptoms. Differences in study setting and diagnostic definitions accounted for a significant proportion of heterogeneity. Conclusions: MGD appears to be commonly detected in adults aged ≥40 years; however, prevalence estimates vary markedly depending on diagnostic criteria and study design. Given the extreme heterogeneity, pooled prevalence estimates should be interpreted with caution and not as a single global prevalence value. Standardized diagnostic definitions and population-based studies using harmonized methodologies are needed to generate more comparable and clinically interpretable estimates of MGD burden.