Infection, Inflammation, and Poststroke Cognitive Impairment

Abstract

Background Infection and inflammation are dementia risk factors in population‐based cohorts; however, studies in stroke are scarce. We determined the prevalence of infection after stroke and routinely measured inflammatory biomarkers during hospitalization and their associations with acute and 6‐month cognitive impairment. Methods and Results A prospective stroke cohort completed the Oxford Cognitive Screen at ≤2 weeks and 6 months after stroke. Infection, inflammatory markers (C‐reactive protein, white cell count, and neutrophil/lymphocyte ratio), and systemic inflammatory response syndrome were ascertained throughout admission with electronic patient records supplemented by hand searches. Associations with acute and 6‐month global and domain‐specific cognitive impairment were analyzed using multivariable regression, adjusting for demographic/vascular factors and stroke severity. Among 255 patients (mean age, 73.9 [SD, 12.6] years; 46.3% women; mean education, 12.6 [SD, 3.7] years; median National Institutes of Health Stroke Scale score 5 [range, minimum‐maximum, 0–30]), infection was present in 90 patients (35.3%) at mean 4.4 (SD, 6.9) days after stroke, consisting predominantly of pneumonia (47/90; 52%) and urinary tract infection (39/90; 43%). Admission white cell count was elevated in 25.1% (n=64; mean, 9.5×10 9 /L [SD, 3.2×10 9 /L]), C‐reactive protein in 41.2% (n=105; mean, 27.5 [SD, 50.9 mg/L]), neutrophil/lymphocyte ratio in 55.7% (n=97; mean, 5.5 [SD, 4.5]), and systemic inflammatory response syndrome in 26.6% (n=53 [45.2%] positive during hospitalization). Infection was associated with acute and 6‐month poststroke cognitive impairment ( P <0.05 adj ) with stronger associations acutely for severe infection (infection+systemic inflammatory response syndrome; P =0.03 adj ). Acute language, executive function and attention domain impairments, and 6‐month number processing impairment were associated with infection ( P <0.05 adj ). No significant relationships were found for any biomarker and cognitive impairment. Conclusions Infection and elevations in routinely measured inflammatory biomarkers are common following stroke; however, only infection is associated with poststroke cognitive impairment, suggesting that increases in these biomarkers may be nonspecific. Infection may present a tractable target for reducing poststroke cognitive impairment.