In a study out of Johns Hopkins University that was published in the December 2014 issue of the Journal of Molecular Biology, researchers found that the amount of mitochondrial DNA found in blood directly correlated with frailty and longevity 10-15 years before symptoms appeared. Patients were followed over 10-20 years looking at the amount of mitochondrial DNA (mtDNA) there was in their blood.
When patients met the criteria for frailty (weakness, decreased energy, lower activity, and weight loss) they had 9% less mtDNA in their blood and the bottom 31% of those people studied met the criteria for frailty. High levels of mtDNA translated into a median of 2.1 extra years of life. They also found that women had about 21% more mtDNA than men, which could partially explain why they live longer!
There is another way to measure DNA's ability to utilize oxygen, it is called a cardiopulmonary exercise stress test. This does not involve taking a blood sample and provides us with an estimate of our biological age.
