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.