Association of HbA1c with VO(2max) in Individuals with Type 1 Diabetes: A Systematic Review and Meta-Analysis

The aim of this systematic review and meta-analysis was to evaluate the association between glycemic control (HbA(1c)) and functional capacity (VO(2max)) in individuals with type 1 diabetes (T1DM). A systematic literature search was conducted in EMBASE, PubMed, Cochrane Central Register of Controlled Trials, and ISI Web of Knowledge for publications from January 1950 until July 2020. Randomized and observational controlled trials with a minimum number of three participants were included if cardio-pulmonary exercise tests to determine VO(2max) and HbA(1c) measurement has been performed. Pooled mean values were estimated for VO(2max) and HbA(1c) and weighted Pearson correlation and meta-regression were performed to assess the association between these parameters. We included 187 studies with a total of 3278 individuals with T1DM. The pooled mean HbA(1c) value was 8.1% (95%CI; 7.9–8.3%), and relative VO(2max) was 38.5 mL/min/kg (37.3–39.6). The pooled mean VO(2max) was significantly lower (36.9 vs. 40.7, p = 0.001) in studies reporting a mean HbA(1c) > 7.5% compared to studies with a mean HbA(1c) ≤ 7.5%. Weighted Pearson correlation coefficient was r = −0.19 (p < 0.001) between VO(2max) and HbA(1c). Meta-regression adjusted for age and sex showed a significant decrease of −0.94 mL/min/kg in VO(2max) per HbA(1c) increase of 1% (p = 0.024). In conclusion, we were able to determine a statistically significant correlation between HbA(1c) and VO(2max) in individuals with T1DM. However, as the correlation was only weak, the association of HbA(1c) and VO(2max) might not be of clinical relevance in individuals with T1DM.