These factors include: knockout of AQP4 [11]; sleep [37]; anaesthesia (especially that incorporating the α2 adrenoceptor agonists xylazine or medetomidine) [37, 201]; traumatic brain injury [15]; age [177]; posture [202]; ablation of meningeal lymphatics [203]; small vessel disease [19]; idiopathic normal pressure hydrocephalus (iNPH) [116]; stroke [14]; and hypercapnia [159]. The gene discussed is AQP4; the disease is Stroke.