Proximal HbA1C Level and First Hypoglycemia Hospitalization in Adults With Incident Type 2 Diabetes.

Context: Hemoglobin A1C (HbA1C) is an important predictor of severe hypoglycemia.

Objective: To determine the association of proximal HbA1C level with first hypoglycemia hospitalization (HH) in adults with incident type 2 diabetes (T2D).

Design, Setting, And Participants: A nested case-control study was designed using linked data from the Clinical Practice Research Datalink and Hospital Episode Statistics in England in 1997 to 2014. The first hypoglycemia event as primary diagnosis for hospitalization after T2D diagnosis was identified. Proximal HbA1C was measured within 90 days before the first HH.

Main Outcome Measure: OR for developing HH.

Results: The association of proximal HbA1C level with first HH was similar between HbA1C levels of 6.0% (OR, 1.54; 95% CI, 1.12 to 2.11) and 9.0% [1.48 (1.01 to 2.17)] compared with the reference HbA1C level of 7.0%. For proximal HbA1C level of 4.0% to 6.5%, every additional 0.5% increase in HbA1C was associated with lower first HH risk, with ORs (95% CI) ranging between 0.37 (0.20 to 0.67) and 0.86 (0.76 to 0.98). For proximal HbA1C level of 8.0% to 11.5%, every additional 0.5% increase in HbA1C was associated with higher first HH risk, with ORs (95% CI) ranging between 1.16 (1.04 to 1.29) and 1.34 (1.18 to 1.52). The U-shaped association between proximal HbA1C level and first HH did not exist among current sulfonylurea users but persisted among current insulin users (Pinteraction = 0.002). Among current noninsulin nonsulfonylurea users who had a first HH, 78% took insulin or sulfonylureas before the HH.

Conclusions: Having either poor or near-normal HbA1C was associated with a higher risk of first HH within 3 months in T2D.