Increased risk of recurrent stroke in patients with impaired kidney function: results of a pooled analysis of individual patient data from the MICON international collaboration.

Background
Patients with chronic kidney disease are at increased risk of stroke and frequently have cerebral microbleeds. Whether such patients also encounter an increased risk of recurrent stroke has not been firmly established. We aimed to determine whether impaired kidney function is associated with the risk of recurrent stroke, and microbleed presence, distribution and severity.Methods
We used pooled data from the Microbleeds International Collaborate Network to investigate associations of impaired kidney function, defined as estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2. Our primary outcome was a composite of recurrent ischaemic stroke (IS) and intracranial haemorrhage (ICrH). Secondary outcomes included: (1) individual components of the primary outcome; (2) modification of the primary outcome by microbleed presence or anticoagulant use and (3) microbleed presence, distribution and severity.Results
11 175 patients (mean age 70.7±12.6, 42% female) were included, of which 2815 (25.2%) had impaired kidney function. Compared with eGFR ≥60, eGFR <60 was associated with a higher risk of the primary outcome (adjusted HR, aHR 1.33 (95% CI 1.14 to 1.56), p<0.001) and higher rates of the recurrent IS (aHR 1.33 (95% CI 1.12 to 1.58)). Reduced eGFR was not associated with ICrH risk (aHR 1.07 (95% CI 0.70 to 1.60)). eGFR was also associated with microbleed presence (adjusted OR, aOR 1.14 (95% CI 1.03 to 1.26)) and severity (aOR 1.17 (95% CI 1.06 to 1.29)). Compared with having no microbleeds, eGFR was lower in those with strictly lobar microbleeds (adjusted mean difference (aMD) -2.10 mL/min/1.73 cm2 (95% CI -3.39 to -0.81)) and mixed microbleeds (aMD -2.42 (95% CI -3.70 to -1.15)), but not strictly deep microbleeds (aMD -0.67 (95% CI -1.85 to 0.51)).Conclusions
In patients with IS or transient ischaemic attack, impaired kidney function was associated with a higher risk of recurrent stroke and higher microbleeds burden, compared with those with normal kidney function. Further research is needed to investigate potential additional measures for secondary prevention in this high-risk group.