I curated this 2015 Georgia human study only for its use of two methods of estimating biological age. The researchers misguidedly used these techniques to help paint a scientific patina on an agenda.
One of the methods was originated by a coauthor of The degree of epigenetic DNA methylation may be used as a proxy to measure biological age study. He compared his technique with the other technique here:
- His technique used the same 353 DNA regions (CpGs, cytosine and guanine separated by only one phosphate link) across different tissues to compare tissue/organ ages;
“The DNA methylation levels of 193 of these markers increase with age but the remaining 160 markers show the opposite behavior.”
- His technique had a Pearson correlation coefficient of r=0.96 with chronological age in this 2013 study;
- The other technique:
“Works poorly for blood samples from subjects who are younger than 20.”
That such methods were available calls into question why the researchers of A study of biological aging in young adults with limited findings didn’t avail themselves of these techniques. They used techniques that were less informative such as telomere length. As an example of how that study’s methods were known to be limited, this 2009 study found that the correlation between chronological age and telomere length was r = −0.51 in women and r = −0.55 in men.
http://www.pnas.org/content/112/33/10325.full “Self-control forecasts better psychosocial outcomes but faster epigenetic aging in low-SES youth”