Association of Variability in Haemoglobin A1c with Cardiovascular Diseases and Mortality in Chinese Patients with Type 2 Diabetes Mellitus – A Retrospective Population-based Cohort Study

Abstract Aims This study aimed to investigate the association between variability in HbA1c and incidence of cardiovascular disease (CVD) event and mortality amongst Chinese primary care patients with Type 2 diabetes mellitus (T2DM). Methods A retrospective cohort study was conducted on 91,866 T2DM patients aged≥18years without any history of CVD. Variability in HbA1c, was measured by standard deviation (SD), associated with the risks of CVD and all-cause mortality were evaluated using Cox proportional hazards regression analysis by age groups (< 65 and ≥ 65 years old). Results Over a median follow-up of 58.5 months, our study identified a positive linear relationship between variability in HbA1c and incidence of CVD and all-cause mortality in the younger and older groups. For every 1-SD increase in HbA1c, the risk of CVD events in the older group only increased by 15.2% (95%CI: 1.026-1.293), and the risks of all-cause mortality in both age groups increased by 49.5% (95%CI: 1.154-1.936) and 77.8% (95%CI: 1.563-2.024), respectively. Conclusions The HbA1c variability independently of the mean HbA1c level may provide additional valuable information as a potential predictor for the development of CVD and all-cause mortality in diabetic patients, particularly for the elderly patients.