Although diabetes mellitus is implicated in susceptibility to infection, the association of diabetes with the subsequent course and outcome is unclear.
Design and setting
Retrospective analysis of two multicenter cohorts. We determined the association of pre-existing diabetes on the host immune response, acute organ function, and mortality in patients hospitalized with community-acquired pneumonia (CAP) in the GenIMS study (n=1895) and on mortality following either CAP or non-infectious hospitalizations in the population-based cohort study, Health ABC (n=1639).
Mortality rate within first year, risk of organ dysfunction, and immune responses, including circulating inflammatory (tumor necrosis factor, interleukin-6, interleukin-10), coagulation (Factor IX, thrombin-antithrombin complexes, antithrombin), fibrinolysis (plasminogen-activator inhibitor-1, and D-dimer), and cell-surface markers (CD120a, CD120b, HLA-DR, TLR-2 and TLR-4).
In GenIMS, diabetes increased mortality rate within first year after CAP (unadjusted hazard ratio [HR]=1.41, 95% confidence interval [CI]=1.12–1.76, p=0.002), even after adjusting for pre-existing cardiovascular and renal disease (adjusted HR=1.3, CI=1.03–1.65, p=0.02). In Health ABC, diabetes increased mortality rate within first year following CAP hospitalization, but not after hospitalization for non-infectious illnesses (significant interaction for diabetes and reason for hospitalization [p=0.04]; HR for diabetes on mortality over first year after CAP 1.87, CI=0.76–4.6, p=0.16 and after non-infectious hospitalization=1.16, CI=0.8–1.6, p=0.37). In GenIMS, immediate immune response was similar, as evidenced by similar circulating immune marker levels in the emergency department and during the first week. Those with diabetes had higher risk of acute kidney injury during hospitalization (39.3% vs. 31.7%, p=0.005) and they were more likely to die due to cardiovascular and kidney disease (34.4% vs. 26.8% and 10.4% vs. 4.5%, p=0.03).
Pre-existing diabetes was associated with a higher risk of death following CAP. The mechanism is not due to an altered immune response, at least as measured by a broad panel of circulating and cell surface markers, but may be due to worsening of pre-existing cardiovascular and kidney disease.