Aging Biomarkers – Chronological v Biological Age

Chronological age can be defined as the time measured from an individual’s birth to a particular date. Biological age is more complex, since it positions an individual within its own lifespan and probability of survival, meaning that a 67 year old man with a biological age of 60 is more likely to live longer than a 67 year old man with a biological age of 70. These concepts are related and in some cases the values can be equal but they are not the same thing.

Chronological age is simply a number representing the length of someone’s life to a particular point; therefore it is difficult to associate biomarkers to it since any biomarker with any influence in the capacity for survival would immediately be more related to biological age. A strict chronological age biomarker should be a biological feature that changes over an individual lifespan but doesn’t directly affect the probability for survival.

There are several biomarkers currently being used that don’t influence survival greatly and are related to older individuals, these could be easily called “chronological age biomarkers”. Reduction of the coronal pulp cavity (using radiography) is a very common method used in forensic science, however, in adults most signs of aging like wrinkles and silver hair are features that can manifest at different points in someone’s life and won’t be useful to accurately determine someone’s biological age.

When looking for aging biomarkers that will reveal the biological age of an individual, these can be split between functional (macro) and physiological (micro) biomarkers.

Aging Biomarkers Infographic

Biological Biomarkers

After many decades of research, the scientific community now agrees on 9 hallmarks of aging that relate to physiological processes acting at the cellular level. These are: accumulation of genetic errors due to genomic instability, telomere attrition or degradation, epigenetic alterations, damage of the internal mechanism in charge of quality control for protein synthesis, deregulated nutrient sensing, mitochondrial dysfunction, loss of the capacity to grow and change stem cell exhaustion and altered intercellular communication.

All of the physiological biomarkers considered above provide data about the capacity of the organism to sustain operation of its own processes over time and also about its capacity to withstand different forms of stress.

These nine hallmarks of aging are robust candidates to be considered for any system dedicated to the determination of biological age; however, obtaining accurate measurements of any of them requires a lot of specialized equipment and capable staff, since they cannot be evaluated easily. Some of them like stem cell exhaustion or mitochondrial dysfunction can only be measured by taking a biopsy and performing a longitudinal study in vitro under laboratory conditions, something that most laboratories don’t provide as part of their usual services.

Functional Biomarkers

Fortunately, functional biomarkers are easier to measure and are considered equally valid to measure biological age. These cover both cognitive and physical performance and include visual acuity (Snellen chart), auditory acuity (pure tone audiometry), decision reaction time, grip strength (dynamometers), body mass index (height and weight measurement), blood pressure (systolic and diastolic pressure), lung capacity (spirometer) and memory.

Functional age is a specialized form of biological age, is task-oriented, and can provide valuable information in regards to an individual’s capacity to perform a particular task or its vulnerability within a certain set of conditions.

All biomarkers mentioned in this article have shown correlation with the process of aging in the past, however, a system designed to provide an accurate value for someone´s biological age will have to integrate a large number of these variables at the same time and incorporate an elegant method to accumulate, process and interpret data from a considerable amount of sources.

They don’t want you to hear about the end of ageing

Recently I attempted to crowd fund the Live Forever Manual – 101 practical tips on how to live forever. Didn’t hear about it? It was harder to publicise than I had expected.

The first hurdle was Kickstarter refusing to host the campaign. It decided it was in breach of its “cure, treat, or prevent an illness or condition” restriction. I appealed explaining that this was to be no miracle cure scientifically proven advice on increasing your lifespan. Maybe I should take heart that they at least recognised ageing as an illness to be cured rather than inevitability.

Oh well, I moved the campaign to Indiegogo which are a bit more lax with their rules.

So now to promote it. Although initially (automatically?) happy to take my money, Twitter later deemed the adverts ineligible based on their Unacceptable Business Practices policy – though didn’t explain which part of it – the book wasn’t going to be illegal or drugs and drug paraphernalia so I’m really not sure what their problem was. You don’t get much information even when you appeal.

I even tried offline, in old fashioned print, in Private Eye – a UK satirical magazine. All I got from them was “advert has not been approved” – and this is a publication which accepts classified ads for Thinking Twats’ T-shirts and anonymous bank transfer requests.

Maybe with enough clout, and a paid lawyer, these organisations could be persuaded to change their mind. But an interesting warning to others wanting to promote radical life extension – on top of overcoming the common reluctance in your audience to believe what you’re saying, the people passing on the message may stop them even hearing it in the first place.

20 year long sauna study shows big impact on life expectancy

Researchers from Finland who studied the habits of middle-aged men found an interesting relationship between heart problems and sauna bathing.  In the study, over 2000 middle-aged men were observed over 20 years.

In that time men taking only 1 sauna per week were 3 times more likely to die from heart disease or other causes compared to those taking 4-7 saunas per week. The study also found that the longer the better –20 minute sauna sessions were twice as effective as 10 minutes ones.

I’ve not looked into the detail of the study so maybe the people taking more saunas were also more active (for example saunaing after a gym session) or shared some other characteristic, however the results were normalised for age and known coronary conditions at the start. I’ve also not compared it to mortality rates in Finland for those not taking saunas at all, but on the face of it it looks like good enough evidence that generally saunas are good for you and I’ll be using the one at the gym more often from now on.

sauna frequency cumulative hazard

Source: Association Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality Events – JAMA Internal Medicine – Apr-2015

And thanks to Health Mate UK for pointing out that infrared sauna cabins have similar health benefits.