Introduction: In patients with myocardial infarction (MI), the presence of diabetes mellitus (DM) is associated with worse clinical outcome including elevated mortality. Over years, great efforts were made to improve medical treatment of patients with DM. We aimed to investigate the influence of DM on in-hospital outcomes (including mortality) of patients with MI.

Methods: MI patients with and without DM were analysed regarding in-hospital outcome. The present study was based on data from the German nationwide inpatient sample in the time scale of 2005-2016 (source: Research Data Center (RDC) of the Federal Statistical Office and the Statistical Offices of the federal states, DRG Statistics 2005-2016, own calculations).

Results: The study included 3,307,703 hospitalized patients with acute MI (62.4% males, 56.8% aged ≥ 70 years), of which 1,007,326 (30.5%) cases were coded with DM. A total of 410,737 patients (12.4%) died during hospitalization. While the rate of MI patients with DM increased slightly over time (2005: 29.8% to 2016: 30.7%, β 7.04 (95%CI 4.13-9.94), P<0.001), in-hospital mortality decreased within the observational period from 15.2% in 2005 to 11.5% in 2016 (β -0.36 [95%CI -0.38 to -0.34], P<0.001). The in-hospital mortality rate was higher in MI patients with vs. without DM (13.2% vs. 12.1%, P<0.001) and recurrent MI (defined as recurrent MI in the first 28 days after the first MI; 0.8% vs. 0.6%, P<0.001) occurred more often in MI patients with DM than in those without. Univariate logistic regression analyses confirmed a higher risk for recurrent MI (OR 1.32 [95%CI 1.29-1.36], P<0.001) and in-hospital mortality (OR 1.11 [95%CI 1.10-1.12], P<0.001). While DM was independently associated with an increased number of recurrent MI (OR 1.23 [95%CI 1.19-1.26], P<0.001), multivariate regression analysis did not confirm an independent association of DM with increased in-hospital death in MI patients (OR 0.99 [95%CI 0.98-0.99], P<0.001). Nevertheless, although DM in patients was not an independent predictor of death in MI patients, DM might be a boosting trigger for mortality in co-prevalence with other cardiovascular risk factors. DM was an independent risk factor for pneumonia (OR 1.18 [95%CI 1.17-1.19], P<0.001), stroke (OR 1.18 [95%CI 1.16-1.19], P<0.001) and transfusion of blood constituents (OR 1.15 [95%CI 1.14-1.16], P<0.001). Cardiac catheterization (51.5% vs. 56.8%, P<0.001) and percutaneous coronary intervention (PCI) (37.6% vs. 43.9%, P<0.001) were less frequently performed in diabetics with MI compared to non-diabetics. These findings regarding interventional treatments were confirmed in the multivariate regression models (cardiac catheterization: OR 0.92 [95%CI 0.91-0.92], P<0.001; PCI: OR 0.90 [95%CI 0.90-0.91], P<0.001). In contrast, coronary-artery bypass graft (CABG) surgery was more often performed in MI patients with DM (5.3% vs. 4.4%, P<0.001), as confirmed after adjustment for age, sex and comorbidities in the multivariate regression (OR 1.18 [95%CI 1.17-1.19], P<0.001).

Conclusions: Although adverse in-hospital events and mortality of patients with MI decreased in both diabetics and non-diabetics within the observational period between 2005 and 2016 in Germany, in-hospital mortality and recurrent MI events were more frequent in MI patients with DM in comparison to MI patients without DM. Coronary artery angiography and PCI were less often used in patients with DM.