The prevalence of Type 2 Diabetes Mellitus (T2DM) is expected to rise, increasing the risk of cardiovascular disease. This study explores the relationship between high-density lipoprotein cholesterol (HDL) and glycemic control in T2DM patients, measured by hemoglobin A1c (HbA1c). While HDL is known to confer cardiovascular benefits, its impact on glycemic control remains unclear.

This cross-sectional study analyzed 30,195 Thai adults with T2DM data from the 2018 Thailand DM/HT database. Well-controlled HbA1c was defined as less than 53 mmol/mol (7 %). The study utilized multivariable linear, piecewise linear, and logistic regression analyses to investigate the relationship between HDL levels and glycemic control.

The impact of HDL on HbA1c levels was nonlinear, showing a U-shaped relationship among the study participants with an HDL inflection point of 59 mg/dl. In females, a U-shaped relationship was also observed at the same inflection point, where increased HDL above this level was associated with a rise in HbA1c (Adjusted β = 0.205, P < 0.001). In contrast, a linear model better explained the consistent negative relationship between HDL and HbA1c in males (Adjusted β = –0.076, P < 0.001). Furthermore, in the poorly controlled HbA1c group, a significant U-shaped pattern was observed with an inflection point at 59 mg/dl.

This study found a nonlinear, gender-specific relationship between HDL and HbA1c in T2DM patients. Males with higher HDL are more likely to achieve glycemic control, while a U-shaped relationship is observed in females. Further research is needed to understand the differing correlation between well-controlled and poorly controlled groups.