Coffee consumption and risk of thyroid cancer: a systematic review and meta-analysis of cohort and case control studies.

BACKGROUND AND OBJECTIVES: The risk of thyroid cancer (TC) has been steadily increasing globally, prompting interest in identifying modifiable risk factors. Coffee, rich in bioactive compounds with potential metabolic effects, may influence TC risk, yet the relationship remains unclear. Therefore, this study aims to systematically review and conduct a meta-analysis of observational studies to assess the association between coffee consumption and the risk of TC. METHODS: Comprehensive searches were conducted in major databases through September 2025 to identify appropriate studies. Following the study selection process, relevant data were extracted. Pooled hazard ratio (HR) and odds ratio (OR) with 95% confidence intervals (CIs) were calculated using random-effects models to account for heterogeneity. RESULTS: This meta-analysis of 10 observational (cohort and case-control) studies found no statistically significant association between coffee consumption and TC risk across both study designs. The pooled analysis of four cohort studies (6 effect sizes) yielded a pooled HR of 0.94 (95% CI: [0.74, 1.20], p = 0.645; I² = 31%), indicating no meaningful risk reduction. The pooled analysis of six case-control studies (8 effect sizes) showed a non-significant trend toward a protective effect, with a pooled OR of 0.78 (95% CI: [0.59, 1.03], p = 0.091; I² = 12%), indicating low heterogeneity across the designs. CONCLUSIONS: Overall, the findings suggest that coffee consumption is not significantly associated with an increased risk of TC. Case-control studies indicate a possible protective trend that warrants further investigation, and the low heterogeneity supports the consistency of these results. Nonetheless, additional large-scale prospective studies are needed to confirm these findings and clarify the underlying biological mechanisms. CLINICAL TRIAL NUMBER: Not applicable.