Lower Glycosylated Hemoglobin Is Associated With Lower In-Hospital Mortality in Patients With COVID-19: A Systematic Review of the Literature and Meta-Analysis.

Objective: Poor glycemic control during COVID-19 hospitalization is associated with higher mortality. However, the association between long-term glycemic control, as reflected by the glycosylated hemoglobin (HbA1c) and outcomes has yet to be clarified, with some studies reporting no association. The aim of this study is to determine the association between HbA1c and in-hospital mortality in patients with COVID-19.

Methods: Pubmed, Embase, and Web of Science databases were searched for studies examining the association between HbA1c level and in-hospital COVID-19 mortality. Random-effects meta-analysis was performed. Heterogeneity was assessed using the I2 statistic. Publication bias was assessed using funnel plots.

Results: Among 4142 results, 22 studies were included in the final analysis with a total of 11 220 patients. Lower Hba1c was associated with lower in-hospital mortality [odds ratio (OR), 0.53; 95% CI, 0.37-0.76; I2 81%], in using HbA1c as a dichotomous variable. When only patients with diabetes were included in the analysis, the association remained statistically significant (OR, 0.67; 95% CI, 0.47-0.96). In the subgroup analysis, the association remained statistically significant in studies using as cutoff the HbA1c value of 6.5% (OR, 0.34; 95% CI, 0.15-0.77) and 7% (OR, 0.54; 95% CI 0.32-0.90), but not with greater HbA1c cutoff values; 7.5% and ≥8%. In studies using HbA1C as a continuous variable, HbA1c level did not have a statistically significant association with in-hospital mortality, either in univariate or multivariate analyses.

Conclusion: A better glycemic control prior to hospitalization, as reflected by lower HbA1c, is associated with lower in-hospital mortality in patients with COVID-19.