Smart Measurement of Blood Glucose Levels

I was diagnosed as being diabetic a couple of weeks ago. Luckily it seems to be controllable with a bit of monitoring and couple of pills each day, and hopefully it stays that way. Each day, I have to take readings of my blood glucose level to ensure it is within normal limits. This involves piercing my finger each day with a lancet to draw blood for the meter. It can be quite fiddly and annoying. That meant that by the end of the first week I found myself googling to see if there were any smart watches available that measured blood glucose levels (BGL). Unfortunately, it appeared that there were none, and any of the several that I found which made the claim to have one were most likely scams. With diabetes becoming a growing health issue around the world, I thought there would have to be at least one smart watch manufacturer that had found a way to continuously monitor BGL.

According to the International Diabetes Federation, there are over half a billion people currently living with diabetes, and that number is growing quite quickly. My googling also told me that it is not yet possible to measure BGL using the near infra-red sensors (NIR) found in smartphones and smartwatches as glucose does not have unique absorption peaks in the NIR region, and it is therefore difficult to distinguish it from other chemicals in the blood. It should be possible to use infrared light, or even mid-infrared light-based devices, which have been tested to check their capabilities for the task and found to have reasonable results. Implementing a solution using mid-infrared light into a watch or phone needs to integrate the sources, detectors, and optical components, which all add to the cost and increase the size of the device. If there was a way of taking the measurements using the NIR sensors already integrated into our current devices, things would be much simpler.

Fortunately, scientists have not been sleeping on the problem. A research team led by Tomoya Nakazawa of Hamamatsu Photonics in Japan has recently developed a new way to estimate BGLs from NIR measurements. The secret sauce of the new method is a new blood glucose level index that the team derived from basic NIR formulas. They did that by extracting oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb) signals from NIR measurements. Through the analysis of massive amounts of data on NIR measurements, the researchers realized that the phase delay (asynchronicity) between the oscillating components of the HbO2 and Hb signals is closely related to the degree of oxygen consumption during each cardiac cycle, thereby serving as a gauge for metabolism.

The team then performed experiments to prove the relationship between this newfound metabolic index and BGLs. Initially, they used the NIR sensor on a smartwatch by placing it over the finger of a healthy subject at rest. The subject then consumed different sugary and sugar-free beverages to induce changes in blood glucose. Similar experiments were conducted using a custom smartphone holder with a high-brightness LED. The results of those experiments were promising, and the changes in the metabolic index closely matched variations in blood glucose levels measured by a commercial continuous glucose monitor. Clinical tests on diabetic individuals are upcoming to confirm the applicability of the metabolic index in a real-world context.

Their researcher’s work was published in the Journal of Biomedical Optics.

I, for one, have my money waiting for the first smartwatch offering this feature. Hopefully it comes soon, for the sake of my fingers.