Visit-to-visit HbA1c variability and risk of potentially avoidable hospitalisations in adults with type 2 diabetes receiving outpatient care at a tertiary hospital.

Aims: This study aims to investigate the relationship between long-term visit-to-visit within-person HbA1c variability and hospitalisation outcomes in adults with type 2 diabetes (T2D).

Methods: We conducted a cohort study at a tertiary hospital in Singapore involving people aged 21 to 101 years with T2D who had ≥3 HbA1c tests over 2 years. HbA1c variability was assessed using coefficient of variation (CV), variability independent of the mean (VIM) and HbA1c variability score (HVS). A 1-year follow-up was performed after the last HbA1c measurement to identify all-cause and potentially avoidable hospitalisations (PAH), categorised as overall, acute, chronic and diabetes composites.

Results: The study included 14 923 patients (mean age: 62.9 ± 12.9 years; 55% male). The median HbA1c variability was 8.6% CV (IQR: 5.1-14.3). Higher quartiles of HbA1c variability were associated with greater risks of PAH and all-cause hospitalisations, independent of glycaemic control. Compared to Q1, for example, the risk ratios and 95% confidence intervals for diabetes-related PAH based on HbA1c CV were as follows: Q2, 1.32 (0.93-1.88); Q3, 1.65 (1.18-2.31) and Q4, 2.16 (1.54-3.03). For all-cause hospitalisations, they were as follows: Q2, 0.97 (0.90-1.05); Q3, 1.08 (1.00-1.17) and Q4, 1.16 (1.07-1.26). When stratified by glycaemic control, elevated risk of PAH persisted even in those with optimal glycaemic control. Consistent findings were observed using HbA1c VIM and HVS measures.

Conclusions: In individuals receiving care at specialist outpatient clinics of a tertiary hospital, HbA1c variability is associated with a higher risk of PAH. Comprehensive diabetes management strategies addressing both glycaemic control and variability may offer benefits.