Methyl labels are key to determining whether a gene is being deactivated or read. Observing methylation at specific placements in the genome, scientist found links with cancer and other diseases. Only in certain combinations of DNA called CpGs, can you find methyl groups. Scientists analyze 500,000 levels of methylation to determine if there was a link to survival. They found that there was a connection between methylation and mortality in 58 of the CpGs. Smoking has the biggest effect on methylation and increasing mortality rate. DNA methylation seems to be reversible, so if a person quits smoking their mortality rate will decrease at a high rate.
Overall, DNA methylation seemed to relate most to survival. I think it's kind of a cool concept. It almost seems like if scientists can figure out how to increase methylation or keep it from ever decreasing, maybe life expectancies will continue to grow.