Diabetes-Technology and the Environment: What Do We Have to Consider?

Introduction

All aspects of health care somehow also have a considerable environmental footprint; a recent global assessment estimated this to be between 1% and 5%. ¹ In this publication, there was no separate consideration of the various diseases in terms of their impact on the environment. Considering the number of patients with diabetes (PwD) and all the different drugs, devices, and so on involved in diabetes therapy, a sound assumption is that the ecological “side effects” of diabetes therapy are significant.

The impact of climate change on PwD was discussed several times before; however, the interaction between climate change and diabetes technology (DT) is a somewhat ignored topic.^{2 -8} In the last decades, we have seen a massive increase in the usage of DT year by year. This development is driven by all the positive effects these products have for PwD; they can perform their diabetes therapy more safely and efficiently. However, this in turn harms our environment. The carbon emissions associated with the manufacturing of such products and all the issues with the handling of the (plastic) waste associated cannot be ignored.^9,10 It is of interest to note that there is no publication about the ecological footprint of DT; this can be assumed to be a challenging undertaking.

The Effect of the Environment on Medical Devices

Many environmental factors have an impact on the function of medical devices, also those used for diabetes therapy. ¹¹ In addition to the overall technological manufacturing process, these environmental factors are carefully studied during the clinical development of such devices. One such factor is the environmental temperature. The function of devices used for DT is guaranteed by the manufacturer for a certain temperature range.

Impact of Heat on the Function of Medical Devices Used for Diabetes Therapy

The number of PwD living in countries in which climate change induces an increase in environmental temperature/heat waves will increase massively in the next decades. Because of the vulnerability of PwD to heat, they will represent a disproportionate burden for the health care systems.^12,13 One can speculate that the impaired function of medical devices used for diabetes therapy contributes to this negative development (see below). The impact of heat on devices used for diagnostic purposes (= glucose measurement) and therapeutic purposes (= insulin administration) has to be considered separately.

In general, many of these devices have temperature sensors built-in as a safety measure. Diagnostics devices need information about the temperature to correct measurement results adequately. However, not much is known (= published) about the extent to which such corrections work in daily life, especially with temperatures (far) outside the recommended temperature range. In this case, the devices are supposed to stop functioning to avoid the delivery of erroneous results, as, for example, enzymes used for specific glucose measurements might denature or change form when exposed to hot temperatures. If the devices do not stop functioning, they might deliver incorrect information.

Heat has also an impact on other components that are essential for the proper function of medical devices, for example, batteries might lose capacity earlier than expected. An important practical aspect is that adhesives used to attach the devices to the skin fail, often because of profound sweating.

Diagnostic Devices

Systems for Self-Monitoring of Blood Glucose

Environmental temperature affects the enzymatic reactions used for specific glucose measurement. The blood drop applied on the reaction zone of the test stripes has body temperature; however, when the environmental temperature is well above (or below) this temperature, the measurement result has to be compensated. It can be assumed that the systems used for Self-Monitoring of Blood Glucose (SMBG) do compensate for a range of temperatures when the temperature is in the functional range. In other words, the reported glucose value is practically not or only partly depending on the ambient temperature. Systems used for SMBG are supposed to not provide measurement results if environmental temperatures are outside the specified range.

The temperature sensors most often are built into the housing of the device used for SMBG measurement itself; they measure the temperature inside the device, not in the reaction zone at the tip of the test strips. Therefore in practice, the temperature at the tip of the test strips might be lower than inside the housing, if the measurement is performed at low environmental temperatures and the device was stored in an insulated location (eg, a pocket of the jacket) before the measurement. Subsequently, there might be at least some differences between the temperatures, which might induce measurement deviations.

Two other aspects have to be considered when using systems for SMBG in hot conditions, one is the need for adequate storage of test strips at temperatures <30°C, which is often difficult to do in reality. It is of interest to note that at least one manufacturer of systems for SMBG states that his test strips maintain measurement performance even at a storage temperature of around 50°C (https://diabetes.terumo.com/technology_solution_02/). The other aspect is that exposure to increased environmental temperatures can induce dehydration. This induces changes in the hematocrit, which are known to have an impact on the glucose measurement results if the hematocrit is outside a certain range.^{14 -16}

Systems for Continuous Glucose Monitoring

Also with these systems, enzymatic reactions are used for glucose measurement; however, this measurement takes place in the interstitial fluid in the subcutaneous tissue. One can assume that the temperature around the tip of the glucose sensor remains more or less at body temperature as long as the endogenous physiological systems for controlling body temperature work. However, it remains to be demonstrated that this is the case also in PwD with their impaired ability to react to heat challenges. By the way, it would also be of interest to know whether the function of the glucose sensor is impaired when a PwD develops a fever.

It would also be of interest to know if heat has an impact on the function of the other parts of continuous glucose monitoring (CGM) systems, mainly the parts of the glucose sensor that are attached to the skin itself. Have the manufacturer of CGM systems data about the failure rates during heat waves in comparison with more normal temperatures?

Exposure to heat leads to an increase in skin blood flow. This might shorten the time between changes in blood glucose and those in interstitial fluid. A factor that the algorithms used to provide a glucose measurement result might have to be considered. Also, dehydration might affect the accuracy of the measurement result.

Therapeutic Devices

The absorption of insulin from the subcutaneous depot into the bloodstream is influenced by the local blood flow in the skin. ¹⁷ Higher temperatures induce more blood flow needed to control body temperature. This in turn induces a more rapid absorption of insulin, which hampers the predictability of the time-action profile of a given insulin formulation.^18,19 The onset of action can be assumed to be more rapid, while the duration of action is decreased. In addition, the variability of insulin action might be increased. With prandial insulin, this might impair optimal coverage of meal-related insulin requirements, which can lead to preprandial hypoglycemia or postprandial hyperglycemia. With basal insulin coverage of insulin, requirements between meals and during the night might be more difficult when the duration of insulin action is shorter and insulin action more variable.

The potency of peptides is impaired by heat; they must be stored within a specific temperature range. Given the high sensitivity of insulin (and other peptides used for diabetes therapy) for degradation (at temperatures above 30°C and also when frozen), adequate storage represents a challenge for many PwD during heatwaves (https://shop.medangel.co/). Storage of insulin in fridges also requires some attention. ²⁰

Insulin Pens

Once a PwD has taken his insulin pen out of the fridge, he or she might carry them around with themselves for a couple of days, until the pen is emptied. The pens are exposed to environmental temperatures during these days that are outside the recommended range. There is a considerable risk for insulin degradation while doing so, especially during elevated environmental temperatures and a lot of movements of the pen. Subsequently, the metabolic effect of applied insulin might be impaired. Some options for cooling insulin pens have been developed; however, they are not widely used.

Most of the traditional insulin pens used do not provide any information about their usage; however, the recently introduced “smart pens” provide information about the insulin dose and time of insulin administration. Some of these also offer a new option: continuous temperature measurement (https://www.diabetesms.com/product/dexcom-g6-cgm-system-1 and https://www.medtronicdiabetes.com/products/inpen-smart-insulin-pen-system). ²¹ In combination with information from wearables/smartphones about body movements, these temperature profiles enable the estimation of insulin stability.

Insulin Pumps

Conventional insulin pumps (= with visible insulin infusion sets) and patch pumps (= that are attached to the skin with an adhesive) are carried close to the human body, which means the temperature of the insulin in the reservoir is at or close to body temperature. ²² An increased environmental temperature might lead to even higher insulin temperatures; however, the increase in skin blood flow associated with a more rapid insulin absorption might be the more relevant aspect of insulin pumps as the predictability of insulin action is impaired. If the function of insulin pumps (also of patch pumps) in general is impaired during heatwaves would be of interest to know. The exposure of the insulin in the infusion set to higher temperatures might increase the risk of occlusions. The usage of shorter infusion sets might be of help in such circumstances. With an increase in the insulin temperature, especially when the insulin is used directly after being taken out of the refrigerator, there is a risk of air bubbles, which can have an impact on pump function (which is true for insulin pens as well). ²³

Automated Insulin Dosing Systems

The different aspects mentioned before for diagnostic and therapeutic devices are also of relevance for systems for Automated Insulin Dosing (AID). The AID systems are vulnerable to systematic errors (due to temperature extremes) in glucose measurement or insulin delivery by adjusting insulin delivery to meet target glucose ranges. The problem in theory occurs when the abnormal function of the glucose sensor or insulin pump is not constant because of fluctuating temperatures and the algorithm then has to continuously change.

Training of Patients (and Physicians/Nurses)

It appears as if the impact of environmental changes on diabetes therapy was not a topic that PwD were trained about until now. There is a need to inform PwD when it comes to heat exposure about adequate storage of insulin and how this factor might impair the function of the medical products used for diabetes therapy.

In case a heat wave is approaching, physicians might consider adjusting their own daily routines and providing respective information to their patients; especially to those known to be of higher risk. They might also recommend measures to avoid issues, like systems that protect insulin pens, usage of shorter insulin infusion sets, changing the insulin reservoir more often, and so on.

Summary

In summary, one has to acknowledge that the interaction between DT and the environment goes in both directions: The usage of DT has an impact on the environment, but environmental factors, like heat, have a clear impact on DT as well. It can be assumed that DT has a considerable ecological footprint. A practically important aspect is the impact heat has on the function of the different systems used for glucose monitoring and insulin administration. We have to acknowledge limited (scientific) knowledge about the impact of heat (and other environmental factors) on medical devices used for diabetes therapy in daily life. There is a clear need for adequate training of PwD (and physicians/nurses) about such aspects. Manufacturers might consider providing warning signals to PwD if a respective medical device was exposed to very low/high temperatures. If the products are exposed to extreme temperatures, a lock-out of the devices might be advisable to avoid erroneous measurement results or device failures.