The emperor's new biomarker? Another wearable for us to evaluate

The bio-hacking community was disrupted last week by news of a novel biomarker - one measured by a wearable on the temple. It's aptly named 'Entropy', apt because of the chaos its revelation unleashed. The name, however, is not apt for what it's purported to measure: amount of energy consumed by the body. So, it shows a minimal value during periods of deep rest (sleep or deep meditation), and a maximal reading during periods of intense activity.

Individuals with some knowledge of thermodynamics will point out the difference between energy and entropy. Measuring energy expenditure is not the same as measuring entropy - a sophisticated concept that can be approximated as the degree of randomness or chaos within a system. Of course, 'Entropy' as a biomarker name is much more marketable than, say, 'Energy,' or any synonymous term such as 'Calorie'.

'Enthalpy,' a thermodynamic property that measures the total heat content of a system, would have been technically flawless, but is commercially hopeless. Possibly, terms such as 'Fire,' 'Shakti,' 'Prana,' or the slang-ier 'Josh' could have fitted the bill.


More than the nomenclature, attention should, however, be directed to the claims made around measurement accuracy and possible benefits of measuring this marker. For Entropy, this data is still in early stages.

I have written previously about the lack of rigorous scientific evidence linking wearables use and real physiological improvements. Common wearables worn simply as wrist bands or body bands track heart/pulse rate metrics, sleep patterns, breath patterns. Continuous glucose monitoring (CGM) has gained traction even with its requirement to insert a tiny filament into the skin. There is a wide range of accuracy in wearables.

My experience has been that even a basic measure, such as heart rate (as measured by the wrist pulse rate), has a massive error rate (of up to 20%) when compared with the pulse rate measured with a finger-on-the-pulse method (either on wrist or neck). Any calculated metric such as heart rate variability based on these measured base values will carry along the error rates.

In addition to inaccuracy, the other equally important concern is the lack of proven benefit of using such tracking. For example, there is no clinical data in a large population to support the use of continuous glucose monitoring in individuals without diabetes. The optimal target of 80-110 mg/dl for glucose control that is being pushed onto this non-diabetes population is without evidence, and is heavily influencer-driven to promote their own nutrition and supplement plans. All this is doing is forcing people to eschew some of their favourite foods without any actual benefit.

Entropy is still in the early part of its lifecycle. Independent of the scientific data it will generate, basic human bias towards action will play a role in its adoption. Wearing and tracking give us the feeling that we are doing something - that the issue is being monitored even if not completely addressed - especially if the action is risk-free. As long as such a bias exists, we will be keen to adopt newer technologies and amuse ourselves with tracking all sorts of information, including 'entropy'.

If thermodynamics has to keep fuelling our biomarker names, then the esoteric term 'Fugacity' should be a leading contender. This term is common in chemical engineering, and is used when dealing with mixtures. It approximates the thermodynamic activity of each component in a mixture.

'Fugacity' comes from the Latin root 'fugere,' which means to flee. Higher fugacity suggests a higher tendency to 'escape' or to mix into another phase. In Marathi, the word 'fuga' means a gas-filled balloon. This delightful match between the etymology of 'fuga' and all the smoke being blown around - and mirrors being shown - in the bio-hacking world puts Fugacity at the top of the list of perfect names for the next biomarker on the market.

The writer is MD, Resonance

Laboratories, Bengaluru