2nd Edition of International Obesity and Metabolism Conference 2026

Abstract

Introduction: Previous studies have examined the association between single waist circumference (WC) and thyroid cancer. However, because WC can vary over time, a single WC measurement does not reflect dynamic changes in WC. Therefore, the present study aimed to investigate the association between longitudinal WC trajectories and the incidence of thyroid cancer.

Methods: A total of 227,182 participants (mean age 61.17 ± 8.00 years) from the National Health Insurance Service–Health Screening Cohort were included in this study. Group-based trajectory modelling was used to identify distinct WC patterns between 2009 and 2014. Associations between WC trajectories and thyroid cancer risk were assessed using Cox proportional hazards models.

Results: Four distinct WC trajectories were identified: low, medium, high, and very high. The very high WC trajectory was associated with significantly increased risk of thyroid cancer in both Models 1 (unadjusted for baseline WC) and Model 2 (fully adjusted for baseline WC). In Model 2, which represents the main analysis, the very high WC trajectory was also associated with an increased risk of thyroid cancer (hazard ratio [HR] 1.41; 95% confidence interval [CI] 1.12–1.77; p < 0.001).

Conclusion: This study suggests that dynamic changes in WC over several years are associated with thyroid cancer incidence. These findings underscore the importance of longitudinal WC monitoring for more accurate prediction of thyroid cancer risk.