The relationship between fasting blood glucose, glycated hemoglobin, fructosamine, and depression in patients with type 2 diabetes mellitus in South Korea: a secondary analysis of the Korea National Health and Nutrition Examination Survey VIII-2 (2020) data

Purpose: This study examined the associations between fasting blood glucose (FBG), glycated hemoglobin (HbA1c), fructosamine, and depression among adults with type 2 diabetes mellitus (T2DM) using nationally representative data from the Korea National Health and Nutrition Examination Survey (KNHANES).Methods: A descriptive cross-sectional study was conducted using secondary data from the second year (2020) of the eighth KNHANES. Adults diagnosed with T2DM were included. Depression was assessed using the Patient Health Questionnaire-9. Complex-sample analyses were applied to account for the survey design, and hierarchical multivariable logistic regression analyses were performed to evaluate associations between glycemic indices reflecting different temporal windows and depression.Results: Depression was not significantly associated with FBG. In contrast, depression prevalence was significantly higher among participants with normal fructosamine levels, whereas it was significantly lower among those with normal HbA1c levels. Younger age and smoking were associated with higher odds of depression, while cohabitation and employment were associated with lower odds.Conclusion: Among adults with T2DM, glycemic indices representing different time frames demonstrated distinct associations with depression. Long-term glycemic control, as indicated by HbA1c, was associated with lower odds of depression, whereas intermediate-term glycemic control, reflected by fructosamine, showed an opposite association. These findings underscore the importance of considering the temporal characteristics of glycemic markers when interpreting their relationships with depression and highlight the need for longitudinal studies to clarify underlying mechanisms.