The influence of self-monitoring blood glucose frequency on the oscillation of hemoglobin A1c and chronic complications.

Background: A fluctuating blood glucose level is one of the risks of chronic complications in diabetes. Previous studies indicated that hemoglobin A1c (HbA1c) values apparently improved after initiation of self-monitoring blood glucose (SMBG). The purpose of this study is to investigate the relationship between the frequency of SMBG, long-term fluctuatation of HbA1c, and risks of chronic complications in diabetes.

Methods: We enrolled 1052 patients with type 2 diabetes. The mean follow-up was 4.7 years. The HbA1c level and frequency of SMBG were recorded every 3 months. Non-mydriatic retinal photography, semiquantitative neuropathy assessment, the lipid profile, serum creatinine level, and urine protein were measured at the beginning of the study and then every year. The fluctuation in HbA1c throughout the period was expressed as the standard deviations (SDs) of all measurements of the HbA1c.

Results: The frequency of SMBG was significantly and negatively correlated with the SDs of the HbA1c (r = -0.553, p < 0.001) but not with the average HbA1c. After controlling for age, sex, body mass index, duration of diabetes and comorbidities (dyslipidemia and hypertension), the correlation was still apparent (r = -0.511, p = 0.008). Patients with progression of nephropathy, neuropathy, and retinopathy, exhibited greater fluctuation of HbA1cs (2.38 ± 0.99 vs. 0.93 ± 1.16, p-value 0.002; 0.97 ± 1.59 vs. 0.90 ± 0.56, p-value 0.04; 0.99 ± 1.33 vs. 0.90 ± 0.56, p-value 0.04, respectively) and less frequent SMBG (3.2 ± 2.6 vs. 4.3 ± 3.1, p-value 0.02; 3.2 ± 2.6 vs. 4.1 ± 3.9, p-value 0.05; 3.0 ± 3.1 vs. 4.2 ± 2.8, p-value 0.01, respectively) than patients without progression of these complications.

Conclusion: This study shows that frequent SMBG decreased the fluctuation of HbA1c and decreased microvascular complications. Decreasing fluctuation of HbA1c may play an important role in diabetes treatment.