Continuous Glucose Monitoring in Older Adults: What We Know and What We Have Yet to Learn

Abstract

Objective:

To assess the growing use of continuous glucose monitoring (CGM) systems by older adults and explore additional areas integration that could benefit adults with frailty.

Background:

The use of CGM devices has expanded rapidly in the last decade. This has been supported by substantial data showing significant benefit in glycemic metrics: hemoglobin A1c improvements, less hypoglycemia, and improved quality of life. However, sub-populations, such as older persons, exist where available data are limited. Furthermore, frail older adults represent a heterogeneous population with their own unique challenges to the management of diabetes. This group has some of the poorest outcomes related to the sequela of diabetes. For example, hypoglycemia resulting in significant morbidity and mortality is more frequent in older person with diabetes than in younger persons with diabetes.

Method:

We present a concise literature review on CGM use in the older adult as well as expand upon glycemic and nonglycemic benefits of CGM for patients, caregivers, and providers. Retrospective analysis of inpatient glycemic data of 16,935 older adults with Type 2 diabetes mellitus at Atrium Health Wake Forest Baptist indicated those with fraility managed with insulin or sulfonylurea had the highest rates of delirium (4.8%), hypoglycemia (3.5%), cardiovascular complications (20.2%) and ED visits/hospitalizatoins (49%). In addition, we address special consideration of specific situations including inpatient, palliative and long term care settings.

Conclusion:

This review article summarizes the available data for CGM use in older adults, discusses the benefits and obstacles with CGM use in this population, and identifies areas of future research needed for improved delivery of care to older persons with diabetes.

Introduction

The continuous glucose monitoring (CGM) technology was initially utilized for the management of type 1 diabetes mellitus (T1DM). The first CGM was available in 1999, and the first CGM augmented continuous subcutaneous insulin infusion (CSII) insulin pump was available in 2006. Advanced applications for automated insulin dosing (AID) became commercially available in 2016. ¹ In the last decade, there has been a growing population of patients with type 2 diabetes mellitus (T2DM) benefiting from CGM for close monitoring; 37.3 million people in the United States (11.3%) have diabetes, and 8.5 million of those remain undiagnosed. ² Older adults represent the fastest growing population with diabetes (29.2% in 2021) and a high-risk population for hypoglycemia.^2,3 Barriers for patients’ use of CGM improved in July 2021 with the Centers for Medicare and Medicaid Services (CMS) eliminating the requirement of four fingerstick blood glucose (FSBG) checks to qualify for coverage. Later, this expanded, in April 2023, to a broader population of those with diabetes on one injection of insulin per day or with documented hypoglycemia.^4,5 Although CGM use is steadily increasing in the outpatient setting, CGM has yet to receive the Food and Drug Administration (FDA) approval for inpatient use. ⁶ Expanded utilization of inpatient CGM during the coronavirus disease 2019 (COVID-19) pandemic, upon the FDA’s emergency use authorization, greatly altered the trajectory of rapid integration of this technology in the inpatient setting. Newer frontiers of CGM application have recently expanded to evaluate use in the perioperative setting to target adequate glycemic control.^7,8 In particular, the growing population of older adults with diabetes represents an opportunity to utilize CGM technology in new and innovative ways: reducing the risk of hypoglycemic and hyperglycemic events in not only the ambulatory setting but also in the inpatient setting given the high rates of acute-care utilization in older adults. CGM technology has potential promise for advancing clinical care delivery and improving both outpatient and inpatient workflows for older adults.^9,10

Glycemic targets for evaluating time in range (TIR), time above range (TAR), time below range (TBR), glycemic variation, and glycemic management indicator (GMI) have been well established and include age considerations when assessing glycemic control. Given the primary goal of limiting hypoglycemia in older or high-risk patients with T1DM or T2DM, instead of typical standards like TIR of 70% for a hemoglobin A1c (HbA1c) level of ~7% with TBR <4% (<70 mg/dL, 3.9 mmol/L) and severe hypoglycemia <1% (<54 mg/dL, 3.0 mmol/L), there is a shift to target TIR of 50% for HbA1c of ~7.9% with TBR <1% (<70 mg/dL, 3.9 mmol/L) in this high-risk population. ¹¹ Recent guidelines recommend consideration of inpatient CGM for adult patients treated with insulin in noncritical care settings who are at high risk of hypoglycemia in conjunction with confirmatory FSBG. ¹² Remote monitoring with CGM proved to be exceptionally useful in the inpatient setting for patients with COVID-19 and hyperglycemia, as this technology aided in targeting adequate glycemic control under strict isolation precautions while reducing healthcare professional exposure for checking FSBG.^13,14

Overview of Evidence for CGM Use in the General Population

Ground-breaking randomized controlled trials (RCTs) evaluating the use of CGM largely occurred initially in the pediatric and younger adult populations only for T1DM and demonstrated improvement in HbA1c without worsening rates of hypoglycemia. ¹⁵ In the DIAMOND RCT, adults with T1DM on multiple daily injection (MDI) therapy over a 24-week duration noted reduction from baseline HbA1c of 1.1% at 12 weeks and 1.0% at 24 weeks in the CGM arm with reduction in TBR to 43 min/day in the CGM arm versus 80 min/day in the control arm. ¹⁶ Similar HbA1c lowering was noted in the RCT by Martens et al ¹⁷ who evaluated adults with T2DM managed with MDI or noninsulin glycemic medications, noting a reduction by −1.1% in the CGM arm versus −0.6% Hb A1c reduction in the FSBG arm. Additional studies, such as the IMMEDIATE study, support the use of CGM for improving T2DM in those with suboptimal control who are not yet on insulin and note improved TIR by 9.9% (2.4 hours) when CGM is utilized alongside diabetes education. ¹⁸

Overview of CGM Use in Older Adults

The prevalence of diabetes increases with age. Among individuals living longer, older adults with diabetes is an important group who need evidence-based interventions. Continuous glucose monitoring efficacy studies that solely focus on older adults are few. Many of the studies rely on post-hoc analysis and are vague regarding implementing CGM technology in older adults with individual needs and limitations. ¹⁹ Pratley et al ²⁰ showed that CGM was superior to FSBG in reducing hypoglycemia for those older than 60 years with T1DM. Subgroup analyses of the MOBILE study and DIAMOND study showed CGM was superior to FSBG in reducing HbA1c and improving TIR in older adults with T2DM and T1DM.^21,22 A recent publication by Leite et al ²³ evaluated adherence and efficacy of CGM for older adults with T2DM requiring insulin and noted a significant reduction in TBR within the 6-week study period. An additional study by Kahkoska et al ²⁴ demonstrated ways to model tailored and age-specific education with the use of strategic feedback loops for older adults with T1DM and their caregivers in order to promote effective ongoing use of CGM. In addition to significant reductions in hypoglycemia, there has also been a demonstrable cost-effectiveness to utilizing CGM instead of FSBG in older adults. ²⁵ The available data are promising, and trends of CGM use in older adults assessed from the Diabetes Prospective Follow-up Registry indicate that utilization of CGM in older adults is increasing. ²⁶

Nonglycemic Benefits of CGM to Patients, Caregivers, and Providers

We have described the positive effects of CGM on glucose metrics including reducing hypoglycemia, lowering HbA1c, and increasing time in target glucose range. In addition to these important outcomes, real-time CGM (rt-CGM) has been shown to improve patient quality of life and sense of well-being in older adults. ²⁷ Studies have evaluated quality of life in adults with T1DM or T2DM treated with insulin without prior CGM use, and find that CGM allowed for significant reductions in diabetes distress including emotional burden, regimen distress, and interpersonal distress. ²⁸ The use of CGM improved anxiety related to hypoglycemia, decreased avoidance behaviors, and improved patient glucose monitoring satisfaction. ²⁹ Other studies have noted use of CGM decreasing caregiver anxiety as well as improved sense of security from caregiver following implementation of CGM. ²⁴ A limitation of many of these studies is that they did not specifically evaluate the quality of life and emotional effects of CGM in older adults.

Many older adults with diabetes struggle with fear of hypoglycemia. With CGM, the easy access to real-time glucose data helps lessen that fear. Many older patients also express frustration with the burden of managing diabetes including administering medications based on multiple blood sugar checks per day. Continuous glucose monitoring allows for some of that burden to be lifted and allocation of that mental energy elsewhere. The available CGM systems include the ability to share real-time glucose data with caregivers and providers. This has expanded the use of telehealth for managing patients with diabetes. ³⁰ Because of this, providers are able to give data-driven recommendations regarding medication changes between face-to-face office appointments. CGM has also allowed for those living in remote rural areas to be provided care by diabetes specialists they would ordinarily not have access to due to long distances. Caregivers of older adults benefit from shared low and high blood glucose alerts allowing for prolonged independence of the patient and peace of mind for the family member.

Adoption of CGM and Barriers in Older Adults

The CMS has eased the criteria for CGM coverage to those being treated with any form of insulin and/or those with hypoglycemia. However, many questions remain. Older adults are a heterogeneous group, and it is unclear if all the purported benefits of CGM apply to every older adult. For example, older adults with cognitive dysfunction may repeatedly react to low and high alerts, resulting in severe fluctuations in blood glucose readings. Those with vision and hearing impairments may have difficulty seeing CGM data or acting on alarms and alerts. Utilization of any glycemic device can include challenges regarding manual dexterity in older adults who may have physical limitations with inability to place CGM devices without assistance. One study by Psavko et al ³¹ assessed the ease of use of CGM in older adults and noted reduced cognitive burden and improved usability with subsequent advancements and reduced number of tasks required to place a CGM with a new generation of devices studied. In addition, utilizing a personal smartphone as a receiver for CGM may be a barrier for patients who are not familiar with this technology. These patients may require support in educating on how to utilize such applications on a smartphone. Additional support from clinic staff is also required to facilitate connecting CGM data to the provider or clinic which the patient follows to have meaningful transfer of glycemic data.

It is notable that aspects of CGM use are different between individuals with T1DM and those with T2DM. Most older adults with T1DM have been managing their diabetes for decades and are more likely to have a strong foundation in diabetes education and management. Older adults with T1DM often started frequent daily blood glucose checks at diagnosis, and thus, CGM provides significantly more freedom and an improved sense of control over their diabetes, while minimizing finger sticks in the outpatient setting. It remains crucial to educate all patients with DM on benefits and limitations at the time of CGM initiation.

Additional Specific Situations: Inpatient, Palliative, and Long-term Care Inpatient

Inpatient CGM use is rising, but data are lacking on outcomes specific to older adults in an inpatient setting. The same applies to CGM use in skilled nursing facilities and again supports the need for more studies in this clinically diverse population. Hypoglycemic events carry potentially fatal risks for older adults^32,33 at a high cost to the healthcare system. The cost of hypoglycemia associated with the use of insulin and sulfonylureas to achieve control for older adults has been estimated at $509,214,473 per year in the United States. ³⁴ While common, hypoglycemia is rarely medically captured; 50% to 70% of older adults with T2DM taking anti-diabetic medications will report hypoglycemic symptoms,^35-39 but only 28% capture objective low blood glucose, ³⁹ and <10% have Medicare claims related to hypoglycemia.^39,40 Hypoglycemia occurs more commonly in frail older adults, whose physiologic changes slow the counterregulatory response to hypoglycemia and mask adrenergic symptoms, producing hypoglycemic unawareness. ³⁹ ,^41-43 Neuroglycopenic symptoms such as dizziness and confusion predominate, which can complicate the presentation of hypoglycemia. ⁴² Severe hypoglycemia (≤54 mg/dL and/or symptoms) doubles with each decade of life after age 60 ⁴⁴ and increases 1.3- to 3-fold with intensive glycemic control. ³⁷ ,^44-46 Risk is highest among black/African American patients^47,48 and among those with cognitive impairment, kidney disease, hypertension, and diabetes duration of >10 years.^36,44

The authors conducted a retrospective analysis of electronic health record (EHR) data for patients attributed to an Accountable Care Organization (ACO) affiliated with their health system (Atrium Health Wake Forest Baptist, Winston-Salem, NC). Of the 16,935 older adults with T2DM followed for one year, those with frailty (6196, 36.6%) had the highest rates of ED visits/hospitalization (46.9%), falls (7.2%), delirium (4.3%), cardiovascular complications (18.1%), and hypoglycemia requiring medical attention (2.1%). Those with frailty on sulfonylurea or insulin (3166, 51.1%) had the highest rates of delirium (4.8%), hypoglycemia (3.5%), cardiovascular complications (20.2%), and ED visits/hospitalizations (49%). These data support the need to manage diabetes in frail older adults differently and use every tool available to prevent hypoglycemia. ³

The hospital setting holds specific additional challenges for older adults with diabetes. ⁴⁹ Both hypoglycemia and high glycemic variability can drive delirium, an acute confusional state highly prevalent, and under-recognized, in the hospital setting and more likely for those with frailty and/or cognitive impairment.^50,51 Furthermore, the events driving hospitalization—whether acute illness or a perioperative state—impose stressors on older adults, and these stressors often reveal underlying frailty or cognitive impairment that a person’s resilience may have previously masked. Specifically, as noted earlier, older adults under stress of a hospital setting may exhibit impaired fasting glucose, hypoglycemia, and glycemic variability, displaying a diminished capacity for maintaining homeostasis in the setting of a stressor event. ⁵² This augments the importance of objective testing for older adults receiving insulin or other glucose-lowering agents.^27,53

Palliative and Long-term Care

Minimizing painful fingersticks can allow for incorporation of CGM in the palliative care setting to be of significant benefit for management of DM, as care should be focused on avoiding symptomatic severe hyperglycemia and hypoglycemia while limiting unnecessary medication burden. CGM may be of benefit for those patients with T1DM transitioning to palliative care settings with continuation of basal insulin to avoid diabetic ketoacidosis. In addition, the lack of globally defined protocols has contributed to the slow acceptance and use of CGM in long-term care (LTC) centers, which are highly regulated organizations. The knowledge surrounding the use of CGM and views of nursing support staff remain unclear in LTC settings. We recommend further research to answer these questions. The settings in which older adults with frailty and/or cognitive impairment receive care may have challenges in working with CGM. Older adults with cognitive impairment may struggle with intermittent scanning, and most skilled nursing facilities do not have the resources to monitor blood glucose via CGM. ³⁶

Case Consideration with Frailty in an Older Adult

The development and use of CGM has re-defined how we deliver care to those living with diabetes. As CGM technology advances, we continue to find new indications for the technology. The following is a case study exemplifying this. A frail 62-year-old woman with history of chronic myelomonocytic leukemia (CMML) presented to our hospital for a planned bone marrow transplantation (BMT). Endocrinology was consulted for inpatient management of her T2DM. Her home regimen consisted of metformin only, with the most recent HbA1c level of 6.9%. However, upon receiving high-dose dexamethasone, she developed severe hyperglycemia. She was placed on basal and bolus insulin and was monitored on our hospital’s standard four-times-daily FSBG checks. Her hospital course was complicated by severe thrombocytopenia with a nadir platelet count of 3000/µL (reference range 150 000-450 000/μL). In an attempt to minimize needle sticks and bleeding risk, the primary team stopped FSBG checks and correctional insulin with the plan to use twice-daily blood draws from the patient’s peripherally inserted central catheter (PICC) line to monitor blood sugar values. As an alternative, the endocrinology consult team offered to provide a personal CGM with the app downloaded onto the patient’s smartphone for both her and the nursing staff to review readings. The patient, primary team, and bedside nursing staff were very enthusiastic about this option, with the patient requesting a personal CGM upon discharge. This frail older woman had an increased risk of hypoglycemia, and CGM was instrumental in reducing that risk. This is just one example that supports the case for expanded use of CGM in nonstandard clinical scenarios.

Future Research Considerations

Research studies often compare older adults with those in youth or middle age, with a typical defining line of 65 years or older. However, older populations are characterized by significant heterogeneity between older individuals,^52,54 with the greatest interindividual variability of health and day-to-day function often occurring between 60 and 90 years of age. ⁵⁵ For example, individual older adults may differ from others in cognitive status, functional independence (ability to carry out daily activities), and in physiological domains such as blood pressure, bone mineral density, or fasting glucose.^52,54 Concepts such as multi-morbidity^56,57 and frailty^58-60 have emerged from the gerontology literature to help characterize older adults in whom the age-associated accumulation of physiological and functional deficits has overcome resilience strategies for homeostasis, resulting in subgroups of older adults who are more prone to adverse health outcomes, independent of the severity of individual disease states. This variability is notable in the setting of glucose control, where even in those without known diabetes, fasting glucose and glucose tolerance test results exhibit a heterogeneity that increases with age. Both frailty and dementia hold a complex bidirectional relationship with T2DM and seem to increase the likelihood of hypoglycemic episodes, in the presence of either T1DM or T2DM.^61,62 In such patients with frailty and with cognitive impairment, it is recommended to pursue de-escalation of therapies that place patients at risk of hypoglycemia including sulfonylureas and rapid-acting insulins as well as individualize glycemic HbA1c targets based on degree of frailty. ⁶³

While CGM use in the inpatient setting for older adults is promising as a tool for achieving adequate glycemic control while minimizing and even preventing episodes of hypoglycemia, there remain numerous areas in need of further research to promote evidence-based technology for this population. Evaluating a meaningful integration in the electronic medical record system that could span across the various inpatient settings, including intraoperative and postoperative periods, as well as for older adults requiring LTC and rehabilitation, is an understudied aspect of CGM utilization. Other considerations of assessing the utility of CGM in subgroups of older adults with a heterogeneous array of functional and cognitive limitations are needed. Engagement with multidisciplinary teams, such as pharmacists and nurse educators, will expand the reach of innovative programs to improve diabetes outcomes. The important roles of health disparities, social deprivation, barriers in utilizing CGM technology, as well as how to approach end-of-life care are each needed. We suggest that future studies evaluate how to best incorporate caregivers alongside multidisciplinary teams to incorporate glycemic data from CGM to provide improved individualized care plans for older adults with DM across the continuum of clinical care.

Candidacy for CGM in the Older Adult

Selecting the ideal candidate for utilization of CGM in the older adult patient population begins by first identifying those at increased risk of frailty and hypoglycemia. Given considerations of potential patient’s physical, visual, and/or auditory limitations, supporting caregiver use of CGM for ease of monitoring glycemic data to prevent hypoglycemia is of great importance. We encourage evaluating each older adult living with diabetes individually to assess their capacity to use CGM technology in an effort to reduce their risk of hypoglycemia. Potential CGM users should be educated on the limitations of interstitial glucose data monitoring and the appropriate response to CGM alerts and alarms. Finally, the specific CGM with supporting device chosen should be tailored to the individual patient. For instance, those who do not own smartphones or who may live in rural areas with limited wireless networking should be provided with a separate reader device in addition to the sensor.

In conclusion, CGM use in older adults is growing rapidly in traditional and nontraditional settings. Providers should be aware of the ideal candidate and best practices to ensure that both the patient and the caregiver receive the benefits of CGM technology. Continued research is needed to provide evidence-based interventions for this important patient population.