A Systematic Review and Meta-analysis Examining the Impact of Age on Perioperative Inflammatory Biomarkers.

BACKGROUND: Dysregulation of immune responses to surgical stress in older patients and those with frailty may manifest as differences in inflammatory biomarkers. We conducted a systematic review and meta-analysis to examine differences in perioperative inflammatory biomarkers between older and younger patients, and between patients with and without frailty. METHODS: MEDLINE, Embase, Cochrane, and CINAHL databases were searched (Inception to June 23, 2020). Observational or experimental studies reporting the perioperative level or activity of biomarkers in surgical patients stratified by age or frailty status were included. The primary outcome was inflammatory biomarkers (grouped by window of ascertainment: pre-op; post-op: <12 hours, 12-24 hours, 1-3 days, 3 days to 1 week, and >1 week). Quality assessment was conducted using the Newcastle-Ottawa Scale. Inverse-variance, random-effects meta-analysis was conducted. RESULTS: Forty-five studies (4263 patients) were included in the review, of which 36 were pooled for meta-analysis (28 noncardiac and 8 cardiac studies). Two studies investigated frailty as the exposure, while the remaining investigated age. In noncardiac studies, older patients had higher preoperative levels of interleukin (IL)-6 and C-reactive protein (CRP), lower preoperative levels of lymphocytes, and higher postoperative levels of IL-6 (<12 hours) and CRP (12-24 hours) than younger patients. In cardiac studies, older patients had higher preoperative levels of IL-6 and CRP and higher postoperative levels of IL-6 (<12 hours and >1 week). CONCLUSIONS: Our findings demonstrate a paucity of frailty-specific studies; however, the presence of age-associated differences in the perioperative inflammatory response is consistent with age-associated states of chronic systemic inflammation and immunosenescence. Additional studies assessing frailty-specific changes in the systemic biologic response to surgery may inform the development of targeted interventions.