Is the frequency of self-monitoring of blood glucose related to long-term metabolic control?: Multicenter analysis including 24,500 patients from 191 centers in Germany and Austria

Blood glucose measurements are generally accepted components of a modern diabetes self-management. The value of self-monitoring of blood glucose (SMBG) is, however, discussed controversially and only a few studies addressed the efficacy of SMBG under real-life conditions so far. In order to investigate whether the frequency of SMBG is related to long-term metabolic control, data from the DPV-Wiss-database, a standardized, prospective, computer-based documentation of diabetes care and outcome, were analyzed for patients with type 1 (n = 19 491) and type 2 (n = 5009) diabetes from 191 centers in Germany and Austria. Local HbA1c reference ranges were mathematically adjusted to the DCCT reference. For each patient, data from the most recent year of diabetes care were used. On average, patients with type 1 diabetes performed 4.4 blood glucose measurements/day. Corrected for age, gender, diabetes duration, insulin therapy and center difference, the SMBG frequency was associated with better metabolic control (HbA1c-reduction of 0.26% for one additional SMBG/day, p < 0.0001). HbA1c-reduction with higher frequency of SMBG was more pronounced in patients on intensified (>= 4 daily injections or CSII) therapy (HbA1c-reduction of 0.32% for one additional SMBG/day) compared to patients on conventional (1 - 3 daily injections) therapy (HbA1c-reduction of 0.16% for one additional SMBG/day). In 2021 patients with insulin-treated type 2 diabetes (2.7 measurements/day), more frequent SMBG was associated with better metabolic control (HbA1c-reduction of 0.16% for one additional SMBG/day, p < 0.0001), while in 2988 patients on OAD or diet alone (2.0 measurements/day), more frequent blood glucose measurements were associated with higher HbA1c-levels (HbA1c-increase of 0.14% for one additional SMBG/day, p < 0.0001). These data indicate that more frequent SMBG are associated with better metabolic control in both, patients with type I and insulin-treated type 2 diabetes. Since no benefit of SMBG on metabolic control was found in patients with type 2 diabetes on OAD or diet alone, SMBG should primarily be recommended for those patients with suboptimal metabolic control whereas the benefit of SHBG in non-insulin-treated patients with adequate HbA1c-levels remains uncertain.