The relationship between inflammatory biomarker trajectory and cognitive change following elective non‐cardiac surgery in older adults

Abstract Background Surgery in the older patient is associated with short‐ and long‐term cognitive changes, including delirium, post‐operative cognitive dysfunction (POCD) and neurocognitive decline (NCD). The inflammatory response to surgery may be a contributing factor. We investigated the association between inflammatory biomarkers and cognitive change up to 3 months following surgery. Method We recruited 70 older adults undergoing elective non‐cardiac surgery. Baseline and 3 month neurocognitive and functional assessments were performed, and delirium was assessed for 5 days following surgery. A control group of age‐similar subjects underwent assessment at similar time points. Blood was collected in 55 patients at baseline and post‐surgery at 30 min, 6h, 24h and 48h for inflammatory biomarker analysis (Tumor Necrosis Factor (TNF)‐α, Interleukin (IL)‐6, IL‐10, IL‐18). POCD was attributed if there was ≥ 1.96 SD decline in two or more neuropsychological tests compared with time‐matched controls. NCD major and mild was attributed according to DSM‐V criteria. Result Patients underwent a range of non‐cardiac surgical procedures and were aged 69.5 (SD 6.7)y and 48.6% were female. Mean baseline MMSE was 27.1 (7.5). Delirium was identified post‐operatively in 4% of subjects. At 3 months, 18 (32.7%) subjects had some form of cognitive decline: POCD 7%, Mild NCD 16% or Major NCD 15%. IL‐6 was significantly elevated following surgery and remained so to 48h. IL‐10 was elevated at 6h but declined to baseline by 48h. Both IL‐18 and TNF‐α were transiently lower than baseline at 30 minutes, but then returned to close to baseline levels. There was no association between inflammatory biomarker levels and delirium or cognitive change at 3 months. Conclusion We have confirmed the presence of new cognitive decline in a significant number of older patients up to 3 months following non‐cardiac surgery. We identified changes in inflammatory biomarkers, especially IL‐6 which was elevated for at least 48h, but no association with cognitive change. Ongoing research will address more specific biomarkers of neuronal injury.