Real-world study of flash glucose monitoring among adults with type 2 diabetes within the Swedish National Diabetes Register
Katarina Eeg-Olofsson et al. NDR
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Abstract
Background:
The Swedish National Diabetes Register (NDR) initiated registration of the FreeStyle Libre® system and other continuous glucose monitoring (CGM) systems in June 2016. We investigated change in HbA1c for people with type 2 diabetes (T2DM) using FreeStyle Libre in Sweden.
Methods:
We included adults with T2DM, registered in the NDR after January 1, 2014, and an index date for first use of FreeStyle Libre of June 2016 or later. Methodology was a before/after comparison of HbA1c within 6 months before the index date versus HbA1c around 6 and 12 months after the index date.
Results:
711 adults with T2DM using FreeStyle Libre had HbA1c measurements within the study period. Mean HbA1c was significantly reduced at 6 months (0.50%-unit) and at 12 months (0.52%-unit) in this group. Degree of change was negatively correlated to baseline HbA1c. Reductions in HbA1c were observed in incident users of FreeStyle Libre with T2DM who were truly na ̈ıve to CGM or had unknown prior experience of CGM, and aged 25–74 years.
Conclusions:
This real-world study on the Swedish NDR shows that people with T2DM using FreeStyle Libre system for 6 and 12 months significantly reduced their HbA1c.
Utdrag ur artikeln
Introduction
In Sweden, approximately 5.5% of the population have diabetes,1 the majority of whom have type 2 diabetes (T2DM).
The Swedish National Diabetes Register (NDR) was founded in 1996 and is an integral part of diabetes care in Sweden, covering both primary and secondary care. The NDR aims to monitor and help improve diabetes care, reducing diabetes-related morbidity and enabling comparisons between a number of important clinical outcome measures.
Nationwide registration of people with diabetes in Sweden is encouraged at least once a year. By January 2019, the register covered 435,093 adults recorded as having diabetes during the pre-ceding 12 months, The NDR includes approximately 90% of all patients aged ≥18 years diagnosed with T2DM in Sweden. Healthcare providers report continuously directly to the NDR or via electronic patient records from routine clinical practice.1
In June 2016, the NDR initiated documentation of the usage of sensor-based continuous glucose monitoring (CGM) including flash glucose monitoring with the FreeStyle Libre® system (Abbott Diabetes Care, Witney, Oxon, UK) amongst adults with diabetes and thus created the oppor- tunity to systematically investigate the impact of the FreeStyle Libre system in Sweden.
Since 2018, the Swedish National Board of Health and Welfare has rec-ommended sensor-based glucose monitoring for people with type 1 diabetes (T1DM), and also for people with T2DM who are treated with multiple daily insulin injections and have problems with recurrent hypoglycemia or hyperglycemia.2,3
Landmark studies have proven that good glucose control, as measured by reduced glycated hemoglobin A1c (HbA1c), is strongly associated with lowered risk of diabetes complications for adults with T2DM.
The UK Prospective Di- abetes Study4,5 demonstrated that a lowering of HbA1c is associated with clinically significant reductions in micro-vascular complications and long-term macrovascular disease.
Randomized clinical trials (RCTs) indicate that, in comparison to self-monitored blood glucose (SMBG) testing, real-time CGM systems can reduce HbA1c in people with T2DM on insulin therapy.6
In studies using the FreeStyle Libre system to date, the REPLACE7 RCT, showed no change in HbA1c over / 26 weeks comparing the FreeStyle Libre system with SMBG in the total study population, whereas one other RCT8 and several real-world observational studies9–11have shown significant reductions in HbA1c amongst adults with T2DM on insulin or non-insulin therapy using the FreeStyle Libre system.
The aims of this study were:
(a) to assess the data collected within the NDR, regarding both the incident and prevalent users of the FreeStyle Libre system amongst individuals with T2DM in Sweden since mid-2016, stratified by type of diabetes treatment and
(b) to analyze changes in recorded HbA1c levels in people with T2DM, before and after initiating the FreeStyle Libre system, including sub-
group analyses according to prior metabolic control and age.
Discussion
The main findings of this retrospective cohort study using the Swedish NDR are revealing as they relate to change in HbA1c amongst incident users of the FreeStyle Libre system with T2DM. Across the study period 3202 adults with T2DM had at least one registered use of the FreeStyle Libre system in the NDR between 1st June 2016 and 25th June 2019 (Table 1). Amongst this population, HbA1c measurements were available within NDR such that it was possible to analyze this aspect of glycemic performance for 711 adults with T2DM before and after the index date for FreeStyle Libre use.
Equally, HbA1c data in NDR enabled an assessment of metabolic control prior to the index date, such that the association be- tween change in HbA1c and use of flash glucose monitoring in adults with T2DM could be evaluated in this context.
For incident users of FreeStyle Libre with T2DM, the NDR data reveal a significant association between FreeStyle Libre use after the index date and reductions in lab- oratory measured HbA1c.
There was an observed decrease in HbA1c across the total incident population of 0.5%-unit at 6 months which was maintained at 12 months. Within the incident user group with T2DM, those truly na ̈ıve to prior use of CGM experienced reductions in HbA1c of 0.67%- unit at 6 months and 0.66%-unit at 12 months. P
eople with unknown prior use of CGM also achieved reductions in HbA1c, both at 6 months (0.43%-unit) and at 12 months (0.49%-unit). This significant but lower reduction compared to truly na ̈ıve users is arguably because of the presence in this group a significant proportion of people with no previous experience of CGM.
This is supported by the observation that the group of incident users with docu- mented prior experience of CGM did not experience a significant change in HbA1c at either timepoint (Figure 1). However, it must be noted that the user group with prior experience of CGM is a small proportion (<7%) of the total incident user population at both timepoints.
These significant reductions in HbA1c observed in T2DM in our study are comparable with those previously reported in smallerscale RCTs and real-world studies for adults treated on insulin or non-insulin therapy, who have no documented prior experience of flash glucose monitoring.8,9,11
Truly na ̈ıve users withT 2DM on insulin treatment will benefit from using the system as a result of the technical and psychological support that comes from short-term and longer-term awareness of trends in their daily glucose levels, allied to the immediate feedback that they get about impending hypoglycemia or prandial excursions.14,15
Some of the users with unknown prior use of CGM will see the same benefit, as they will in reality also be na ̈ıve. Others in this group will have prior undocumented experience with CGM and can have developed behaviors that aid in improved daily glucose control, independent of the device itself.
The value of good glucose-control behaviors independent of the application of FreeStyle Libre is also supported by the data on HbA1c change observed for the separate groups of users stratified by baseline HbA1c prior to the index date (Table 4) and insulin use status.
Incident users of the FreeStyle Libre system with better initial control, as evidenced by baseline HbA1c <8.0%, did not achieved any significant change 6 months after the index date, irrespective of their insulin or non-insulin treatment status. It is possible that the glycemic control objective for this group is focused on avoiding hypoglycemia whilst maintaining their HbA1c, rather than reducing it further.
In our study, reductions in HbA1c at 6 months after the index date were more notable for incident users with higher starting baseline values ≥8.0% and greatest for those with HbA1c ≥12.0%. These observations are in line with smaller real-world studies indicating that the degree of change in HbA1c for people with diabetes using the FreeStyle Libre system is directly correlated with baseline HbA1c in T2DM.8,9,16
It is clear from our data that significant reductions in HbA1c across the total population of incident users at 6 months after the FreeStyle Libre index date are driven by substantial reductions in those individuals with higher baseline HbA1c measurements.
Our analysis of the data from the NDR show that the benefits of reduced HbA1c after initiating the FreeStyle Libre system are extended across adults aged 25–74 years old with T2DM who are confirmed insulin users (Table 5).
Non-insulin users did not show a change in HbA1c, however this group contained mainly people with T2DM and good baseline glycemic control with HbA1c <8.0% (Table 4) where change was also not significant in the insulin user group.
Our study could not confirm a previous prospective study on 49 individuals with T2DM on non-insulin therapy and a baseline HbA1c of 7.8% which did show a significant reduction (0.46%-unit; p < 0.001) at 24 weeks.11 However, comparisons cannot be realistically drawn between a prospective RCT and our retrospective real-world analysis.
Another important outcome from our data is that im- provements in glycemic control amongst adults with T2DM on insulin aged 66–74 years are achievable using the FreeStyle Libre system. This extends previous studies reporting significant reductions in HbA1c using CGM in subjects with a mean age of 67 years with T2DM.17
Use of sensor-based glucose monitoring systems in older and elderly people with diabetes has focused on reducing the adverse risks and consequences of hypoglycemia and hyperglycemia in this high-risk population18,19 rather than directly reducing HbA1c.
Although our data cannot be interpreted in this context, they do indicate that improvements in long-term glycemic control are possible for older people with T2DM. Although the reductions in HbA1c appear to be attenuated in the 66–74 years age group compared to the 25–65 year old subjects (0.35% versus 0.72%), it is not possible to conclude whether this is due to a genuine age- dependent response to using the FreeStyle Libre system, or whether it reflects the known correlation between the scale of reduction with starting HbA1c,9,16 since the baseline HbA1c of the 66–74 years age group is 8.3% compared to 8.9% amongst the 25–65 years age group.
Further research on the response of younger versus older people with T2DM using the FreeStyle Libre system is likely to be valuable.
In this context, it must be acknowledged that HbA1c is only one aspect of glycemic control, and that other measures of glycemic health in T2DM are improved by using the FreeStyle Libre system, such as frequency and time spent in hypoglycemia,7 which could be of more value in older populations, compared to change in HbA1c.
Conclusions/summary
This real-world observational study on a large cohort of individuals with diabetes seen in clinical practice, has shown that people with T2DM in Sweden can significantly reduce their observed HbA1c for at least 12 months following initiation of the FreeStyle Libre system.
These reductions are evident by 6 months after starting with flash glucose monitoring and the degree of change in HbA1c is correlated with the baseline HbA1c of users prior to ini- tiation.
Across the age distribution of users, significant reductions in HbA1c for people with T2DM were evident for all adults 25–74 years old. This analysis has significant implications for person-centered clinical care in diabetes and also for long-term health economic outcomes in the treatment of diabetes at a national level.
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https://journals.sagepub.com/doi/pdf/10.1177/14791641211067418
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