The New Wave of Health Sensors

About two years ago, as a 68-year-old decades-long Type 2 diabetes patient, my doctor prescribed a wearable continuous glucose monitoring (CGM) device fully covered by Medicare.

My A1C (blood sugar level) at the time was pushing close to an unhealthy 9.0. I reduced my A1C to 7.1 in five months through intermittent fasting and continuous glucose monitoring. The CGM device gives me 24-hour real-time data on my glucose levels without having to finger-blood-stick for glucose readings nearly as much as I used to.

My CGM system comprises three elements; an applicator that I press onto my abdomen to apply a sensor patch via a button push, a transmitter that slips into the patch and a pocket-sized reader (or I can have readings sent to my smartphone). 

Each prescription comes with three 10-day sensors, and each transmitter, which is a separate prescription, lasts for 90 days. An added benefit is that I don't see my doctor for the recommended Type 2 diabetes patient visits every three to six months for an A1C reading and analysis, but instead, I now see him closer to every 10- to 12 months.

According to recent medical research titled "Digital health for aging populations," published in Nature Medicine by the Department of Nanotechnology at the University of California San Diego on July 18, 2023, wearable glucose monitoring systems have "proven to be extremely useful for reducing risks of hypoglycemia and hyperglycemia." 

UC San Diego professor Joseph Wang, also faculty director of the school's Center for Wearable Sensors, co-authored the Nature Medicine paper. He says CGMs are the most successful commercial wearable sensors on the market today. 

His team at the Center focuses on "developing wearable electrochemical sensors for non-invasive monitoring of a broad range of biomarkers relevant to health and wellness." As explained in the paper, sensing technology comes in four primary categories:

1. Wearable physical sensors. Measures physical signals such as basic vital signs, heart rate, ECG, respiration rate, body temperature, oxygen saturation or blood pressure.
2. Wearable chemical sensors. Tracks the chemical composition of various biofluids, such as sweat, tears, saliva and interstitial fluid (the fluid that fills spaces between cells).
3. Hybrid and multi-parameter sensing platforms. Simultaneously tracks chemical biomarkers and physical vital signs.
4. Non-wearable sensors. These are based on smart home digital systems that monitor older adults' behavior, posture and movement.

Wang added, "Emerging wristband sweat sensing platforms are gaining considerable recent attention." 

As noted in a March 2022 academic paper headlined "Wearable microfluidic-based e-skin sweat sensors," by the Department of Chemistry, National Institute of Technology (NIT) in India, "sweat testing has been employed in diverse applications ranging from medical diagnosis of diabetes, cystic fibrosis, tuberculosis, blood pressure and autonomic neuropathy to evaluating fluid and electrolyte balance in athletes."

Also called body-on-chip devices, the authors from NIT noted that while sweat testing is still a nascent technology, they predict such wearables will "revolutionize the health care system on various fronts in developed and emerging nations. It will significantly reduce the health care system's cost, improve life expectancy by fifteen to twenty years and reduce animal usage for clinical trial."

Peter Nguyen, a scientist at Harvard University's Wyss Institute of Biologically Inspired Engineering, conducts necessary research about wearables and sensing technologies. 

In a July 22, 2022 report titled "End-to-end design of wearable sensors" — co-authored by Nguyen with scientists from the Wyss Institute, the University of Freiburg, Germany; the Imperial College of London; and the Biophotonic Nanosensors Laboratory in Mexico — it was prognosticated that the next generation of wearables will also provide automated treatment.

"Smart bandages, for example, could allow for real-time monitoring of wound healing through pH measurement and, in the case of an infection, treatment by on-demand delivery of antibiotics or anti-inflammatory drugs," the report's authors noted. 

My small CGM will eventually be capable of automatically injecting me with measured insulin doses based on my glucose readings.

Nguyen believes that the next significant invention coming to the world of wearables, in anywhere from one to five years, are smartwatches that continuously take your blood pressure via miniaturized ultrasound technology, thus eliminating the awkward cuffs we so often wrap around our upper arms. 

"These are really tiny micro skilled devices that can emit pulses of ultrasound right over your skin and actually detect your blood vessel enlarging and closing," Nguyen says. "They can do this very complicated calculation that can estimate your blood pressure changing."

Adding sensing technologies to fabrics is another area of research with interesting futuristic implications, perhaps arriving within ten years or more, according to Nguyen. 

During the pandemic, for instance, he and the Wyss team conducted research on the development of COVID-19 fabric masks that could be embedded with what's known as "wearable freeze-dried cell-free technology (wFDCF)," which is also used in home pregnancy tests. 

The wFDCF masks were "able to rapidly and accurately detect the presence of SARS-CoV2 viral RNA in a patient's breath," according to press on this research.

Wearable diagnostic fabric states are started by "basically analyzing a sample using DNA. . . We took the technology, which is DNA sequencing, and we integrated it directly into the fabric. It collects things in the environment and analyzes them," Nguyen explains. 

Like a CGM device, users will get alerted when and if they've been infected with a virus. Nguyen adds that the Wyss Institute has grown interested in further developing fabric-sensing technologies for detecting the flu and tuberculosis. 

Still, the research has experienced delays due to business bureaucracies that stall the work. "The barriers (to further development) have not been scientific barriers. The barriers have been more on the business side," he says.

One technology that Nguyen mentioned that has grown in popularity and has continued to improve is shoe insoles that vibrate, known to improve nerve function for people with foot neuropathy and improve balance and reduce irregular gait in older adults.

"One thing I would tell older adults is just to have an open mind regarding trying these things," Nguyen advises. "Know that some of these are new and might not be perfect [the numerous iterations of different smartwatches and accessories come to mind] – but try them out. You might find them to be beneficial."

"It's never too late to go digital and take control of your health," adds Wang.