DNA methylation in the TNF-alpha gene decreases along with aging among delirium inpatients

•TNF gene DNA methylation negatively correlated with aging in delirious inpatients.•Such association was confirmed by genome-wide Illumina EPIC array and pyrosequencing.•Such association was found in blood samples and peripheral blood mononuclear cells (PBMC), but not from buccal samples.•The role of epigenetics in pathophysiological mechanism of delirium was suggested. It has been suggested that aging and inflammation play key roles in the development of delirium. In the present study, we investigated the differences of the DNAm patterns in the TNF gene between patients with delirium and without. The data and samples derived from previous and ongoing cohort studies were analyzed. DNAm levels of the TNF gene were analyzed using the Illumina EPIC array genome-wide method and pyrosequencing method. Correlations between age and DNAm levels of each CpG were calculated. Several CpG in the TNF gene in blood showed negative correlation between their DNAm and age in delirium cases both with the EPIC array and by the pyrosequencing method. However, there was no CpG that had significant correlation between their DNAm and age regardless of delirium status among buccal samples. On the other hand, among peripheral blood mononuclear cells samples, it was found that several CpG showed negative correlation between their DNAm and age in delirium cases. The evidence of DNAm change in the TNF gene among delirious subjects was demonstrated.