What are the pros and cons of continuous glucose monitoring?

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For people living with diabetes, blood sugar (glucose) checks are a part of everyday life. The standard way of measuring the glucose levels in the blood is by taking a small sample of blood from your finger and holding it against a test strip attached to a blood glucose meter. This needs to be done several times a day. The advent of continuous glucose monitoring (CGM) could mean an end to people with diabetes needing to prick their fingers so frequently. They could also be helpful for people trying to lose weight. But are they the godsend that they may first appear? Let’s take a look at what are the pros and cons of continuous glucose monitoring.

What is continuous glucose monitoring?

Continuous glucose monitoring is a method of, well, continuously monitoring the glucose in your body. It involves placing a tiny sensor just under your skin that measures your glucose levels, transmitting this information to an external monitor. Some continuous glucose monitoring (CGM)devices, such as the Dexcom G6 and the Eversense Implantable CGM, will sound an alarm when your blood glucose levels are too high or too low.

With many CGM devices, you will also need to conduct fingerstick calibrations a couple of times a day, but others, such as the Abbett Freestyle Libra, don’t require the use of fingerstick calibration at all. When you get a reading that suggests your blood glucose is too high or too low, you can take action either by taking insulin or holding back on taking some.

With the Dexcom G6 and the Eversense Implantable CGM, you can have the results sent directly to your smartphone, and they can then be shared with your healthcare provider. And with all of them, you will be able to see your blood glucose trends, which can give you valuable insight into how your day-to-day life and behavior influence your blood glucose.

CGM devices don’t measure your blood glucose directly. Instead, they measure the interstitial blood glucose, the amount of blood glucose in the fluid surrounding your body’s cells.

What are the benefits of CGM devices?

There is a wide range of benefits that go along with the use of a CGM device, especially for people living with diabetes. Firstly, they reduce or eliminate the need for frequent finger-prick testing, which can become quite a burden for many people. They can be particularly useful for people with diabetes who often have hypoglycemia unawareness. This is when you have low blood glucose but don’t experience any symptoms associated with it. You can be warned that your blood glucose is getting low before it becomes a problem by continuously monitoring your blood glucose.

The ability to send rich data to your healthcare provider is also an essential benefit of CGM devices. It can help them to understand the situation with your diabetes in much greater detail, which they can use to make medication decisions or to give you lifestyle advice.

Which is more accurate: fingerstick or CGM devices?

As we have touched on, CGM and fingerstick monitoring work slightly differently. A fingerstick monitor will directly test your blood glucose levels by using a small sample of your blood. On the other hand, CGM devices don’t measure your blood glucose directly and instead measure the glucose in the fluid surrounding your cells. Both are accurate because they can precisely measure the amount of glucose, but with the method that the CGM devices use, there can be a short delay. This is because it takes more time for your interstitial glucose to change.

This can mean that you won’t always get accurate results using this method, especially immediately after an activity that will change your blood glucose levels, such as eating a meal or exercising. However, with that being said, because you are continuously monitoring your glucose, you will be able to see that trend even if it is at a short delay.

What are the disadvantages of CGM devices?

While CGM devices might seem like the obvious answer to diabetes, they aren’t without their disadvantages. Many people find that inserting the sensor can be painful, and with most devices, this needs to be done every week or every two weeks. In addition, when a sensor is replaced, the new one needs to be placed at a different spot, and on smaller bodies, this can sometimes be a challenge. Some people also find that the insertion site can get irritated or sore.

There can also be problems with a loss of signal with the connection between the sensor and the CGM device, resulting in losing important data about their blood glucose levels.

Why do people stop using CGM devices?

Interestingly, the data shows that the adoption of CGM devices is remarkably low. It currently lies at between 8% and 17%. Given that CGM devices reduce or eliminate one of the more cumbersome sides of living with CGM, many would expect that number to be higher. Many users who stop using are generally focused on the sensor, including the user burden of needing to insert a new sensor so often and the pain and/or skin irritation that goes along with it.

Some past users of CGM devices that have stopped using them also mention that using a CGM device impacted their body image. Because an external device needs to be placed on the skin near the sensor for the CGM device to pick up the signal, there is a permanent reminder that they have diabetes that is visible to everyone. This can be a particular problem when the device is on the arm, which it will sometimes need to be. As cumbersome as fingerstick tests can be, they are unobtrusive and can be completed in private without anyone realizing.

And the use of a CGM device often doesn’t mean the end of fingerstick testing, so inserting the sensor and monitoring glucose with that method can seem like an additional burden on top of fingerstick testing, which can lead some users to choose one over the other to reduce how much time they have to put into dealing with their diabetes.

What is the future for CGM devices?

While uptake of CGM devices is currently remarkably low, new technologies are always being developed that can reduce or eliminate the reasons why people either don’t use them or stop using them. One of the most important developments has been the closed-loop and fully insertable CGM systems. And there are already products on the market that offers this. For example, the Everense CGM is fully insertable, and the MiniMed is what is known as a closed-loop CGM device.

Closed-loop and fully insertable CGM devices work differently from other CGM devices. Fully insertable means that they don’t have any components that need to be attached externally to the skin, which can reduce the body image issues associated with using a CGM device and problems with lack of adhesion and lost signal. Instead of needing a transmitter on the skin, the fully inserted sensor contains a fluorescent chemical that produces a small amount of light when exposed to glucose, which the monitor can pick up. Crucially, they also don’t need to be changed as often. The Everense implantable CGM sensor has a 90-day life, significantly longer than the 7-14 days that most sensors can last. This reduces the burden and pain associated with so frequently needing to insert a new sensor and could make a CGM more practical on a day-to-day basis for many users.

A closed-loop system detects glucose using the same method as standard CGM devices. The MiniMed, for example, uses a Guardian Sensor beneath the skin that will need to be changed every seven days. However, they differ in the automatic way in which they deal with changes to blood glucose. Rather than giving off an alarm that tells the user they need to take or reduce their insulin, the MiniMed is attached to an insulin pump that will automatically adjust insulin levels when it detects changes to blood glucose levels. This can make a big difference to the lives of people with diabetes because it reduces the mental load of monitoring blood glucose and taking their medication.

The future of CGM devices likely lies in the amalgamation of these two technologies, which will probably happen shortly. A fully-insertable and closed-loop device will be the easiest, less intrusive way for people with diabetes to monitor their blood glucose and their insulin intake, and it would be a single device that eliminates most of the reasons why people either choose not to use a CGM device or who stop using one once they have started.

But that isn’t the only development in the works to monitor blood glucose levels. An exciting new development in this field is the use of smartwatches to measure blood glucose levels. Many of us already use smartwatches to monitor our heart rate, sleep cycle, breathing rate, and more. So why not a smartwatch that works as a CGM device?

And this isn’t just a dream. During the recent CES2022 conference, there were a number of innovative technologies related to diabetes and glucose monitoring. These include Light Touch Technology (LTT) can measure blood glucose levels without needing to take a blood sample using a high-intensity infrared laser, which may be life-changing for people with diabetes. Even those who don’t use a CGM device. And Quantum Operations presented a smartwatch-enabled device that used spectrum-sensing technology to detect blood glucose levels through the skin. 

And there are already smartwatches in development that could be used in the future as CGM devices or as a way of monitoring glucose for everyday health. The Glutrac, for example, doesn’t require the insertion of any sensors and instead uses optical sensors that measure a range of different bodily functions, such as absorption spectroscopy, electrocardiography, photoelectric plethysmography, and dynamic metabolic heat monitoring. Machine learning can use this data to predict when blood sugars are likely to be high or low.

The AerBetic uses nanosensors that can detect glucose levels in your breath, which sounds like science fiction but is based on sound scientific reasoning. We already know that medical support dogs can alert their owners that their blood glucose has changed, and they use their sense of smell to achieve this. The K’Watch uses an external patch with microneedles instead of one that needs to be inserted into the skin. The Kyocera can measure carbohydrate levels in the blood using pulse rate monitoring. 

We have discussed the many issues that users have with CGM devices as they stand today, and uptake is remarkably low, but that doesn’t mean that the idea isn’t sound. A CGM device that constantly measures people’s glucose is still a life-changing device for people living with diabetes, and the reasons why people tend to stop using them or choose not to use them in the first place are often centered around practical reasons that are related to the technology as it is today. 

The CGM devices of the future are unlikely to deal with the same issues that plague the CGM devices of today. Whether that be fully insertable closed-loop systems that reduce the need for painful insertions and monitoring insulin medication, or whether that be smart devices that use machine learning and other technologies to eliminate the need for a sensor to be inserted in the first place, a CGM device that works for everybody isn’t far away. 

To wrap up

Continuous glucose monitoring (CGM) devices can seem like a godsend to people living with diabetes, who often have to take small samples of their blood using a fingerstick monitor multiple times a day. But there are issues with how CGM devices are practical, which means only a tiny percentage of people with diabetes currently use them. Technological advances are changing the landscape entirely when living with diabetes. 

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