Diabetes prevalence and mortality in COVID-19 patients: a systematic review, meta-analysis, and meta-regression

Background The coronavirus disease 2019 (COVID-19) patients with diabetes mellitus (DM) are at high risk of fatal outcomes. This meta-analysis quantifies the prevalence of mortality among (1) diabetic and (2) non-diabetic, and (3) the prevalence of DM, in hospitalized COVID-19 patients. Methods Published studies were retrieved from four electronic databases (PubMed, Embase, Scopus, and medRxiv) and appraised critically utilizing the National Heart, Lung, and Blood Institute's tool. Meta-analyses were performed using the random-effects model. The measures of heterogeneity were ascertained by I- squared (I-2) and Chi-squared (Chi(2)) tests statistics. Predictors of heterogeneity were quantified using meta-regression models. Results Of the reviewed 475 publications, 22 studies (chiefly case series (59.09 %)), sourcing data of 45,775 hospitalized COVID-19 patients, were deemed eligible. The weighted prevalence of mortality in hospitlized COVID-19 patients with DM (20.0 %, 95 % CI: 15.0-26.0; I-2, 96.8 %) was 82 % (1.82-time) higher than that in non-DM patients (11.0 %, 95 % CI: 5.0-16.0; I-2, 99.3 %). The prevalence of mortality among DM patients was highest in Europe (28.0 %; 95 % CI: 14.0-44.0) followed by the United States (20.0 %, 95 % CI: 11.0-32.0) and Asia (17.0 %, 95 % CI: 8.0-28.0). Sample size and severity of the COVID-19 were associated (p < 0.05) with variability in the prevalence of mortality. The weighted prevalence of DM among hospitalized COVID-19 patients was 20 % (95 % confidence interval [CI]: 15-25, I-2, 99.3 %). Overall, the quality of the studies was fair. Conclusions Hospitalized COVID-19 patients were appreciably burdened with a high prevalence of DM. DM contributed to the increased risk of mortality among hospitalized COVID-19 patients compared to non-DM patients, particularly among critically ill patients. Registration: PROSPERO (registration no. CRD42020196589).