Because CGM technology has only recently been made available to the larger public, there is limited data on its adoption and use in diabetes management. Use of CGM has rapidly expanded, increasing from 7,000 users in 2006 to 15,000 users in 2007.32,33
Reports from 2007 projected more than 140,000 users in 2009, but user data for 2011 is unclear.33
Unlike CSII, reimbursement for the cost of CGM devices and supplies varies greatly across insurance providers, so finances can also pose a significant barrier for many patients who might otherwise want to use this technology.
It has been demonstrated that real-time CGM has the ability to improve metabolic control, including lowering HbA1c without increasing the time spent in hypoglycemia, for some individuals with T1DM.34–37
A recent meta-analysis38
of six randomized, controlled trials of two or more months’ duration yielded positive results, with significant reductions in HbA1c with CGM use, especially in those patients with the highest baseline HbA1c levels, as well as those who used the device more. This same study also found some evidence, although weaker, for a reduction in time spent in hypoglycemia. Despite the expected advantages of CGM, more research is needed to determine which patients will reap the most benefits from this technology. In addition, few studies to date have examined the psychological impact of CGM use, including issues related to quality of life and reductions in fear of hypoglycemia. Early results39
indicate that CGM use has neither adverse nor beneficial effects on psychological functioning in youth, but clearly more research is needed. Actual data on level of interest in CGM in the T1DM community is scarce. In one survey40
, 90% of parents endorsed a high level of interest in having their children with T1DM use CGM but only if the cost was covered by insurance. Without insurance coverage, only 50% of parents believed they would use CGM.
It is important for potential users and their families to have realistic expectations about CGM, such as understanding that this technology is not a cure for diabetes, nor is it the artificial pancreas.41,42
Additionally, users should understand that with novelty comes imperfection, including discrepancies between interstitial glucose and BG meter readings, frequent false alarms, and a potentially overwhelming amount of glucose data.41,42
A common unrealistic expectation is that CGM will prevent all episodes of hypoglycemia and hyperglycemia, which, unfortunately, is not accurate. Ideally, a structured assess-ment of patient knowledge of intensive diabetes self-management, as well as patient expectations, would be conducted prior to CGM initiation, to identify those individuals who can most successfully use this technology, as well as those who might need more preparation. As research into patient acceptance and long-term use of CGM continues, it can serve as an essential guide for the development of patient selection, training, and support needed for CLC systems.
Research is just beginning to investigate potential psycho-logical and behavioral barriers to CGM use, and initial findings indicate that patients will need to have the motivation, willingness, and ability to use CGM extremely consistently in terms of the number of hours/days per week that the device is worn. As noted above, a meta-analysis38
of CGM studies indicates that improvements in glycemic control most likely occur in patients who use the device more consistently. In the JDRF CGM trial43
, which was included in that study, use of CGM was more consistent among adults age 25 years or older than in the younger age groups, with 83% of adults averaging at least 6 days of usage per week. Adults 25 years and older also demonstrated a significant reduction in HbA1c levels compared to the younger age groups. Those aged 15–24 years showed the least HbA1c improve-ment, and only 30% of these participants used the device at least six days per week. The fact that CGM may be beneficial in improving metabolic control only for those individuals who will use the technology almost all of the time has important implications for patient selection and education. One factor has been identified that appears to predict greater CGM use, which is pre-CGM frequency of BG monitoring.34
Because this behavioral variable also predicts success with CSII, it should be considered as an important patient selection characteristic for CLC trials.
Psychological factors, such as coping skills and perceived support, have also been identified as predictors of CGM success.44
A recent study comparing adult responders to CGM (improved HbA1c) to non-responders (no improvement) demonstrated the importance of type of coping strategy and perceived social support in reaping glycemic benefits from the device. Although participants in both groups experienced frustrations related to CGM use, responders tended to engage in self-controlled coping strategies (i.e., taking a neutral problem-solving approach), and they reported receiving more support from their significant others. Given the hassle factor that comes with CGM use, which can include frequent false alarms, physical discomfort of the sensor, sensor calibration failures, and discrepancies between CGM interstitial glucose and BG meter readings,45
patients’ ability to cope with these stressors, as well as their willingness to use CGM consistently and make changes in diabetes management behaviors, appear to be predictors of individuals who will fare best with this technology.46
The abundance of glucose data that CGM provides may also render feelings of anxiety.41
It is critical that patients know how to interpret and apply the data that they receive from the system, but there are no published guidelines for outpatient use at this time.47
In response to this problem, the DirectNet Study Group developed the DirecNet Applied Treatment Algorithm, which utilizes algorithms to help patients make diabetes management decisions (i.e., insulin dosing) based on real-time glucose values and downloaded sensor data.47
Promising results of a pilot pediatric study found that, after 13 weeks, all participants and their parents believed the algorithms provided clear instructions and improved postprandial BG excursions.
Not surprisingly, adoption and utilization of CGM requires ample patient education not only on the specific features and functions of the device, but also on how to utilize glucose feedback to improve diabetes self-management.48
Graded, gradual, systematic training is recommended, similar to the education protocols currently in place for initiating CSII.49
An education and training model has been proposed for health care professionals to enhance their efficiency with CGM technology and better train patients in its use.48
Such comprehensive education and close follow-up are likely to be necessary for many patients to achieve optimal glycemic control from CGM.49,50