DNA Methylation at Core NMDA Receptor Genes Reveals a Glutamatergic Signature of Aging in Post-COVID Whole Blood with Implications for Long COVID Neuropsychiatric Sequelae

Background: Cognitive symptoms after SARS-CoV-2 infection, often described as “brain fog,” remain difficult to measure objectively and are biologically heterogeneous. DNA methylation may provide a stable, blood-accessible layer of information linking post-COVID immune remodeling, biological aging, and neuropsychiatric vulnerability. We re-analyzed GSE247869, a whole-blood Illumina MethylationEPIC dataset from individuals sampled six months after COVID-19 infection, to identify age-associated methylation signals with translational relevance.Methods: Processed beta values were aligned to metadata, converted to M-values, and modeled at each CpG using ordinary least squares with age and sex as predictors. Differentially methylated positions were corrected by Benjamini–Hochberg false discovery rate. CpGs were mapped to genes using robust annotation and Illumina manifest fallback. Gene-level signals were integrated using a multi-evidence prioritization score that incorporated statistical strength, effect size, multi-CpG support, direction consistency, known epigenetic-clock membership, and curated pathway membership.Results: The analysis identified 3,467 age-associated CpGs at FDR < 0.05, with an overall hypomethylation bias but focal hypermethylation at canonical aging loci. Eleven of twelve reference clock CpGs were recovered, including ELOVL2, FHL2, TRIM59, EDARADD, ASPA, and PDE4C. The strongest discovery signal was enrichment of glutamatergic/NMDA genes, including GRIN1, GRIN2C, GRIN2D, GRM1, GRM5, and SLC17A7. GRIN1 and GRIN2C had high integrated evidence scores and showed age-associated hypermethylation. These findings converged on glutamatergic synapse, calcium signaling, and cAMP signaling pathways.Conclusions: This re-analysis supports a reproducible aging methylation signature in post-COVID whole blood and raises a testable hypothesis: age-associated methylation changes near NMDA and metabotropic glutamate genes may mark systemic glutamatergic vulnerability relevant to post-COVID cognitive impairment. The findings do not prove COVID-driven age acceleration, because the analysis is cross-sectional, but they support future longitudinal clock-residual, DMR, and biomarker-stratified studies, including studies of Cheung Glutamatergic Regimen-type interventions.Keywords: DNA methylation, long COVID, epigenetic aging, GRIN1, NMDA receptor, glutamate, cognitive impairment, brain fog, calcium signaling, Cheung Glutamatergic Regimen