Associations Between Obesity and Risk of Thyroid Cancer: A Meta-Analysis of Cohort Studies

Previous cohort studies have shown conflicting findings on the associations between obesity and the risk of thyroid cancer. This meta-analysis aimed to investigate the associations between them by using a meta-analysis of cohort studies. PubMed and EMBASE were searched using keywords from inception until November 2023 to identify relevant studies on this topic. Two authors independently reviewed and selected relevant studies according to the predefined criteria. Out of 475 studies searched from the databases, a total of 22 cohort studies were included in the final analysis. In a random-effects meta-analysis, obesity was significantly associated with an increased risk of thyroid cancer [odds ratio (OR), relative risk (RR), or hazard ratio (HR) = 1.33; 95% confidence interval (CI) 1.24 - 1.43]. Obesity was consistently associated with the increased risk of thyroid cancer in the subgroup meta-analyses by various factors such as study type (prospective or retrospective cohort study), gender (male or female), continent (America, Europe, or Asia), and study quality (high or low). This meta-analysis of cohort studies suggests that obesity increases the risk of thyroid cancer.