The glycemic gap and 90-day mortality in community-acquired pneumonia- A prospective cohort study

Background: In patients without diabetes (DM) hyperglycemia is associated with high mortality from community-acquired pneumonia(CAP). Hyperglycemia, however, is a common condition among patients with DM and preexisting hyperglycemia should be accounted for in studies of a possible association between hyperglycemia and mortality in patients with DM. Aim: To investigate the association between the glycemic gap (the difference between admission hyperglycemia and the estimated average glucose (EAG)) and 90-day mortality. Methods: A prospective cohort study. EAG was derived from hemoglobin A1c. The absolute-glycemic gap was defined as; “admittance blood glucose - EAG“. The proportional glycemic-gap was defined as; “((admittance blood glucose/EAG)*100)-100”. The association between the absolute-glycemic gap and the proportional-glycemic gap and 90-day mortality was assessed with Cox proportional hazard model. We categorized the proportional-glycemic gap according to quartiles. Results: 1933 adults were included. The absolute-glycemic-gap was not associated with an increased risk for 90-day mortality, HR 1.02 (95% CI 0.93-1.11). Compared to the 2nd quartile, the 1st and 4th proportional-glycemic gap quartile was associated with a higher risk with HR 2.7 (95% CI 1.11-6.65) and HR 2.5 (95% CI 1.05-5.69), respectively. No interaction between DM and the proportional-glycemic gap or the absolute-glycemic gap was found (p=0.82 and p=0.25, respectively). Conclusion: Patients with the lowest and highest proportional-glycemic gap had the highest risk for 90-day mortality and it was not modified by DM. The proportional-glycemic gap might be incorporated into future risk assessment tools for CAP.