Association between Continuity of Care and the Onset of Thyroid Disorder among Diabetes Patients in Korea

Objectives: As the relationship between diabetes mellitus and thyroid dysfunction is well known, it is important to investigate the factors influencing this association. Continuity of care is associated with better quality of care and outcomes, such as reduced complications, among diabetes patients. Therefore, the purpose of this study was to investigate the association between continuity of care and the onset of thyroid dysfunction among diabetes patients. Methods: We used Korean National Health Insurance Service National Sample Cohort data from 2002 to 2013. Our final study population included 16,806 newly diagnosed diabetes patients who were older than 45 years of age. Continuity of care was measured using the Continuity of Care index. The dependent variable was the onset of thyroid disorder. Cox proportional hazard regression models were used for statistical analyses. Results: Diabetes patients with low continuity of care were at increased risk of the onset of thyroid disorder compared with those with high continuity of care (hazard ratio (HR): 1.28, 95% confidence interval (CI): 1.07–1.54). Subgroup analyses showed that this association was significant within patients with type 2 diabetes (HR: 1.24, 95% CI: 1.01–1.52) or whose main attending site was a local clinic (HR: 1.32, 95% CI: 1.07–1.64). Conclusions: Our results show that diabetes patients with low continuity of care are more likely to experience the onset of thyroid disorder. Therefore, improving continuity of care could be a reasonable method of preventing complications or comorbidities, including thyroid disorder, among diabetes patients.