Fluctuations in HbA1c are associated with a higher incidence of cardiovascular disease in Japanese patients with type 2 diabetes

Aims/Introduction: To reveal whether visit‐to‐visit variability in HbA1c is associated with higher risk of cardiovascular disease (CVD) in patients with type 2 diabetes. Materials and Methods: The study was conducted on 689 Japanese patients with type 2 diabetes [295 women, 394 men; mean (±standard deviations (SD)) age 65 ± 11 years]. Variability in HbA1c was evaluated as the intrapersonal SD of serial measurements of HbA1c during the follow‐up period for at least 12 months. Patients were divided into quartiles according to the SD of HbA1c, and the primary endpoint was defined as incident CVD. Cox’s proportional hazards model was used to calculate hazard ratios (HR) and 95% confidence intervals (CI). Results: During a median follow‐up period of 3.3 years (range 1.0–6.3 years), 26 ± 14 measurements of HbA1c were obtained per patient and 61 episodes of incident CVD were recorded. The 5‐year cumulative incidence of CVD in patients across the first, second, third, and fourth quartiles of SD in HbA1c was 4.9, 8.7, 17.1, and 26.2%, respectively (P < 0.001, log‐rank test). Multivariate Cox regression analysis revealed that the incidence of CVD was significantly higher in patients in the fourth quartile of SD in HbA1c compared with those in the first quartile (HR 3.38; 95% CI 1.07–10.63; P = 0.039), independent of mean HbA1c and other traditional cardiovascular risk factors. Conclusions: Variability of HbA1c may be a potent predictor of incident CVD in Japanese patients with type 2 diabetes. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00155.x, 2011)