IntroductionSleep deprivation (SD) impairs cognitive function and induces hippocampal injury, yet the gut-derived mechanisms underlying these deficits remain incompletely understood.MethodsHere, we established a mouse SD model using a modified multiple-platform water environment method and evaluated the effects of oral administration of Lactobacillus acidophilus CICC 22162.ResultsSD caused gut microbial dysbiosis and compromised colonic barrier integrity, leading to hippocampal inflammation, neuronal apoptosis, and synaptic protein loss. Intervention with L. acidophilus CICC 22162 partially restored microbial balance, strengthened intestinal barrier proteins, reduced hippocampal inflammation and neuronal apoptosis, and improved cognitive performance. Fecal microbiota transplantation (FMT) experiments demonstrated that protective effects could be partially transferred via the gut microbiota from treated donors, highlighting the functional role of the intestinal microbial community. Untargeted metabolomics identified S-adenosylmethionine (SAM) as a candidate microbiota-associated metabolite linked to neuroprotection, and in vivo and ex vivo validation showed that SAM reproduced cognitive benefits through α7 nicotinic acetylcholine receptor (α7nAChR)-related signaling, including enhanced JAK2/STAT3 phosphorylation and suppressed NF-κB activation.DiscussionThese findings delineate a gut microbiota–SAM–α7nAChR neuroimmune pathway through which L. acidophilus CICC 22162 alleviates SD-associated cognitive dysfunction, providing mechanistic support for microbiota-targeted interventions against sleep loss-induced cognitive impairment.