Association of elevated serum urea nitrogen and the remaining renal function indicators with recurrence of acute ischaemic stroke, with mediating and interacting effects with blood inflammatory indicators

Background and purpose: The relationship between blood urea nitrogen (BUN) and other markers of renal function and the recurrence of acute ischemic stroke (AIS) have been scarcely reported. Inflammatory mechanisms may play a role in these relationships.The aims of this study were to investigate the relationship between BUN and recurrence of AIS and to explore the roles of inflammatory indicators in these relationships. Methods: A total of 10,973 patients hospitalised for cerebral infarction from 2015 to 2020 were included in this study. BUN, creatinine (CR), uric acid (UA), BUN/CR, UA/CRand BUN/UA were divided into four groups. Cox regression and restricted three-sample bar regression models were used to evaluate the clinical correlations between BUN and other indicators of renal function and ischaemic stroke recurrence. Results: Among the indicators, the risk of ischaemic stroke recurrence was increased by 117.0% (hazard ratios (HR)= 2.170, 95% confidence interval (CI)=1.816–2.593, P<0.001) in patients with the fourth quartile BUN level (Q4 ≥ 6.4 mmol/L), using the first quartile level (Q1<4.3 mmol/L) as the reference value. BUN predicted a greater risk ratio of ischaemic stroke recurrence over 5 years than did the remaining indicators of renal function. We also found that inflammatory markers play a mediating role. Conclusions: Higher BUN levels were associated with recurrent ischaemic stroke events within 5 years. And, the inflammatory markers white blood cell (WBC) count, absolute neutrophil count (ANC), absolute lymphocyte count (ALC) and neutrophil to lymphocyte ratio (NLR) mediated and interacted with BUN and ischaemic stroke recurrence.