During the last decade growing evidence shows the association between the epigenetic dysregulation and cell aging. While many studies have been conducted on the autosomal chromosomes to investigate the age related DNAm changes in both males and females, there were not many studies that included X-chromosomes. We performed X-chromosome analysis to study age associated DNA methylation variation on X-chromosome in Danish male and female twins (492 twins aged 56-80) and their influence on epigenomic instability and its association with X-chromosome inactivation in females. We detected 14 significant CpG sites showing elevated methylation variability in male twins (FDR