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.


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).
Division of Nephrology and Hypertension.
Ryotaro
R
Bouchi
Division of Nephrology and Hypertension.
Tetsuya
T
Babazono
Division of Nephrology and Hypertension.
Michino
M
Mugishima
Division of Nephrology and Hypertension.
Naoshi
N
Yoshida
Division of Nephrology and Hypertension.
Izumi
I
Nyumura
Division of Nephrology and Hypertension.
Kiwako
K
Toya
Division of Nephrology and Hypertension.
Toshihide
T
Hayashi
Division of Nephrology and Hypertension.
Ko
K
Hanai
Division of Nephrology and Hypertension.
Nobue
N
Tanaka
Division of Nephrology and Hypertension.
Akiko
A
Ishii
Department of Medicine, Diabetes Center, Tokyo Women's Medical University School of Medicine, Tokyo, Japan.
Yasuhiko
Y
Iwamoto
Cardiovascular disease; HbA1c variability; Type 2 diabetes