Differences of mean methylation were determined in three tissues (heart muscle, skeletal muscle, liver) for two age groups (group 1: 26 years, SD +/− 4 years and group 2: 68 years, SD +/− 8 years, red line), males/females (orange line) and two different primary cells (CD4+ lymphocytes, dermal fibroblasts, blue line). As control, tissues were re-sampled (10,000-fold) for both age groups and their mean methylation differences were calculated (grey area). The same control was carried out for sex-specific differences and similar results were obtained (data not shown). As positive control for sex-specific methylation, an X-chromosomal gene (ELK1) was used that displays the expected methylation difference of about 50% (green line). While the 7.1% difference between primary cells (blue line) is highly significant, the respective differences of 0.275% and 0.1% between age groups (red line) and sex (orange line) fall within the differential range observed for the control (grey area) and are therefore not significant.