Another calculator says Maya ages 12 years in the first year and 6 in each subsequent year which would make her 90 in human years.

On Pedigree’s website, its dog age calculator goes by breed and in Maya’s case puts her age at 72 in human terms, a years older than me as of January.

It’s clear from the above that there hasn’t appeared to be an exact science on calculating the age of dogs compared to us, that is, until now.

New research studying chemical modifications to DNA over a lifetime, called epigenetics, has come up with the epigenetic clock.

What does the epigenetic clock tell us?

It tracks how sequences in our genetic makeup change from body wear and tear, lifestyle, and disease. The mechanism for the clock is DNA methylation, referring to the presence of methylcytosine found at different levels throughout the lifecycle of human DNA and that of other living things.

In a 2017 research paper entitled “DNA methylation dynamics in aging: how far are we from understanding the mechanisms?” the authors write “DNA methylation is currently the most promising molecular marker for monitoring aging and predicting life expectancy.” 

Using the epigenetic clock, new research is attempting to determine a human-dog age comparison based on similar age-related methylation occurring in the two species’ genomes. Methylations can be seen in young and old dogs and humans, and the rates of change in both are similar. What might explain this is a common evolutionary trait in terms of DNA methylation going back to a common mammalian ancestry. 

States Matt Kaeberlein, a biogerontologist from the University of Washington in Seattle, “We already knew that dogs get the same diseases and functional declines of aging that humans do, and this work provides evidence that similar molecular changes are also occurring during aging…a beautiful demonstration of the conserved features of the epigenetic age clocks shared by dogs and humans.”

Based on the comparison in methylation rates, a 7-week-old puppy is equal in age to a 9-month-old human baby. Then the clocks change as the one for dogs speeds up making 12 dog years equivalent to 70 for humans. DNA methylation in both species increases in aging. And it may vary in different dog breeds which has led some researchers to start the Dog Aging Project.

Getting back to Maya and figuring out an accurate age for her that isn’t based on the three methods described above, when the number 14 gets plug into the epigenetic dog clock in comes out to be 73.2 years in human terms. So the Pedigree calculator isn’t too far off. To read the original paper on dogs and epigenetic clocks, go to the link found here.

That’s been the prevailing notion behind mortality in the scientific community for some time. But now we are finding another lifespan indicator within DNA that can accurately predict our longevity. It is cytosine, one of the four base pair chemicals that creates the double helix in the DNA molecule. The others are adenine, thymine, and guanine.

Studying the epigenetic influences on twins has revealed something startling. Chemical changes to cytosine can be directly correlated to a person’s time of death. The research, done by a UCLA biostatistician Steve Horvath, used 13,000 blood samples collected over time from people already deceased where the date of their death was known. The maintenance of the chemical cytosine turns out to be critical. Cytosine is a nitrogenous nuclease. It contains the hydrocarbon defined by the formula CH3, a carbon atom bonded to three hydrogen atoms. Alterations in the level of CH3 within cytosine acts like a mortality clock strongly influencing the health of the DNA. Horvath has found that the state of CH3 contributes 40% to our time of death. The rest is determined by lifestyle and dumb luck.

Epigenetics is proving to be a better science for studying human lifespan and health than genetics alone. Today researchers do epigenetic profiles of people from post-birth umbilical cord blood and can even predict disease risk. Horvath’s lab has developed an epigenetic lifespan predictor called DNAm GrimAge. It is an epigenetic clock that can more accurately predict the lifespan of newborns rather than that of older people. That’s because lifestyle and dumb luck play a more profound influence on the elderly but not with newborns who are just starting out.

As clocks go Horvath’s Grim Reaper has a significant margin of error even though it is a better indicator of lifespan certainty than any previous tool. Of course, it can’t predict you getting hit by a bus and succumbing while crossing a street.

When Horvath tested himself he found to his horror that his body was 5 years older than his actual age. That’s not the best news for a scientist in search of a tool that will help define longevity.

So how do you maintain healthy cytosine and hence increase your lifespan?

The process of cytosine deterioration is called DNA methylation. As you age methylation impacts DNA replication and gene expression. So increasing cytosine content would seem a good thing. For example, could eating healthy foods keep your cytosine up to prolong your life?

Apparently a healthy diet of vegetables and fish can contribute to the slowing of DNA methylation. So can better sleep habits.

Insomniacs beware because you don’t score well with the DNAm GrimAge tool.

What about exercise? So far no data supports exercise as reversing DNA methylation.

If we know how long we have to live what changes?

For life planning, knowing when we are likely to die should give us the motivation to accomplish more in the time we have. For some, it could mean getting as much education done early in life to be able to work and live in a productive and meaningful way. For others, it could mean planning a much earlier retirement to enjoy traveling and other experiences before your time is up.

For the insurance industry, a lifespan clock becomes a way to mitigate the risk and make adjustments in the pricing of premiums related to issuing death benefit policies.

And a lifespan clock could also help physicians determine whether to be aggressive or palliative for a patient with terminal cancer knowing that chemotherapy or invasive radiation would contribute little to extending the person’s lifespan.