Persistent systemic interleukin-6 elevation after community-acquired pneumonia is associated with one-year mortality

Community-acquired pneumonia (CAP) remains a leading global cause of mortality and the foremost infectious cause of death. Emerging evidence suggests that its impact extends beyond the acute phase. In this context, long-term complications involving the cardiovascular system and other organs, as well as increased mortality lasting up to 10 years, have been reported. The aim of our study was to assess systemic inflammation at day 30 after CAP through readily available biomarkers (interleukin-6 [IL-6] and C-reactive protein [CRP]) and its association with long-term (one-year) mortality. We performed a post-hoc analysis of a prospective observational study including 268 patients discharged alive after hospitalisation for CAP, along with 15 healthy controls. The first follow-up took place 30 days after discharge at outpatient clinics, where blood samples were collected. One-year follow-up data were obtained from electronic medical records and telephone interviews. Our findings showed significant higher IL-6 and CRP levels at day 30 after CAP compared to controls, especially, in those who died during the following year. This elevation reflects ongoing low-grade systemic inflammation due to incomplete or slow resolution, or from an inability to restore homeostasis.