Continuous Glucose Monitoring: A Perspective on Its Past, Present, and Future Applications for Diabetes Management

摘要

The transition from urinary glucose measurement to more sophisticated self-monitoring of blood glucose (SMBG) systems in the 1970s and 1980s dramatically changed the approach to and understanding of diabetes management ( 1 ). Innovations in the design and technology of portable blood glucose meters have become integral to the success of intensive treatment of both type 1 and type 2 diabetes, and the outcome of this treatment has led to a tremendous decrease in the development of long-term micro- and macrovascular complications ( 2 – 4 ). However, intensive insulin therapy has its limitations, including increased frequency of hypoglycemia and the need for frequent SMBG testing. In the past decade, continuous glucose monitoring (CGM) technology has evolved into a novel tool to support diabetes management. Unlike conventional glucose meters, which provide a snapshot of the blood glucose value at the time of testing, CGM provides semi-continuous information about glucose levels. It does this indirectly, by extrapolating blood glucose levels from interstitial fluid glucose via an algorithm. Importantly, CGM allows users to make decisions regarding their day-to-day diabetes management using real-time glucose trends. Along with this information, CGM systems provide customizable hypo- and hyperglycemia alarms and display trends of the rate of change of glucose levels. Most recently, CGM systems have been integrated with insulin pumps and are being used in artificial pancreas clinical trials. In this article, we discuss the clinical benefits of CGM; its challenges, including accuracy and user experience; and its present and future role in the management of diabetes. Clinical Benefits of CGM Numerous studies have explored whether sustained use of CGM offers clinical benefits in individuals with diabetes. Randomized, multicenter clinical trials have shown improved glycemic control in adults with type 1 diabetes using CGM compared to those using SMBG and a reduction in the time spent in hypoglycemia with concomitant improvement in A1C for those using CGM technology ( 5 – 10 ). Even in patients with type 1 diabetes whose diabetes was well controlled at baseline with an A1C 180 mg/dL) with stable A1C levels after 6 months ( 11 ). In patients with type 2 diabetes, CGM has also been shown to improve A1C and reduce the time spent outside of glycemic targets, with the largest reduction in patients with a baseline A1C >9% ( 12 , 13 ). Adherence to and frequency of CGM use over time has been a particularly important aspect of the associated reduction in A1C. More frequent CGM use in all age-groups has been associated with greater A1C reduction from baseline to 6 months ( 14 ). Both the Juvenile Diabetes Research Foundation Continuous Glucose Monitoring Randomized Clinical Trial and the Sensor-Augmented Pump Therapy for A1C Reduction (STAR) 1 trial showed that lower A1C levels were observed in patients who used CGM ≥60% of the time ( 5 , 15 ). The STAR 3 trial showed that increased frequency of sensor use was associated with greater A1C reduction, and sensor use >80% of the time resulted in a doubling of the effect ( 16 ). CGM Patient Selection and Clinician Education Important considerations need to be made when recommending CGM therapy. As reported in the American Association of Clinical Endocrinologists (AACE) 2010 consensus statement on CGM, appropriate candidates include individuals with type 1 diabetes who have hypoglycemia or hypoglycemia unawareness and who have an A1C above their target ( 17 ). In 2011, the Endocrine Society released its first CGM guidelines and recommended the use of CGM in adults with type 1 diabetes who can demonstrate that they can use these devices on a nearly daily basis (6–7 days per week) ( 18 ). Similarly, in a white paper based on a 2015 CGM summit, the American Association of Diabetes Educators (AADE) stated that CGM may be appropriate for any person with diabetes who is willing to wear a CGM device, regardless of age, diabetes type, or duration of diabetes ( 19 ). Recently, a 2016 AACE CGM consensus conference suggested that the use of CGM may be especially beneficial for type 1 diabetes patients who are >65 years of age with comorbidities or at risk for severe hypoglycemia, as well as for patients with diabetic chronic kidney disease ( 20 ). Additionally, it suggested that the benefits of CGM therapy also may apply to insulin-treated individuals with type 2 diabetes, as well as pregnant women with diabetes, although more studies are needed in these populations ( 20 ). In its 2015 CGM summit white paper, AADE outlined the benefits of CGM therapy in identifying glycemic excursions, characterizing the effects of physical activity and high–glycemic index meals on glucose levels, and mitigating hypoglycemia frequency and severity via alerts and alarms for impending hypoglycemia ( 19 ). Most importantly, AADE emphasized the need to adequately select and train patients who wish to use CGM techno