Association between khat chewing and temporomandibular disorders: a systematic review and meta-analysis of observational studies

BACKGROUND: Temporomandibular disorders (TMDs) are common chronic conditions that significantly impact patients’ quality of life. This systematic review and meta-analysis evaluated the potential association between khat chewing and TMDs. METHODS: A comprehensive literature search of PubMed, Scopus, Web of Science, and Google Scholar was conducted by two independent investigators on May 26, 2025, to identify all relevant studies. Statistical analyses were performed using Stata/MP v17 (StataCorp, TX, USA). Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. The methodological quality of the included studies was assessed using the Newcastle–Ottawa Scale (NOS). Additionally, GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) system was used to assess the certainty of evidence. RESULTS: Thirteen studies, comprising 3526 subjects, met the inclusion criteria. Of these, only six studies were included in the meta-analysis. Qualitative findings indicated a significant association between khat chewing and the clinical and radiographic signs of TMDs. The pooled analysis demonstrated a significant association between khat chewing and TMDs (OR = 2.48; 95% CI: 1.20–5.09; p = 0.01; heterogeneity: I² = 84.68%). According to GRADE analysis, the overall quality of evidence was very low. CONCLUSION: The available evidence indicates a possible association between long-term khat chewing and TMDs. However, given the low quality of evidence and the considerable heterogeneity among the studies, these findings should be interpreted with caution. Further well-designed longitudinal studies are strongly recommended to clarify the potential detrimental effects of khat chewing on the temporomandibular joint and the masticatory system.