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Adding Glucose-Lowering Agents Delays Insulin Initiation and Prolongs Hyperglycemia
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Adding Glucose-Lowering Agents Delays Insulin Initiation and Prolongs Hyperglycemia

Courtney Hugie, PharmD, BCPS; Nancee V. Waterbury, PharmD, BCACP; Bruce Alexander, PharmD; Robert F. Shaw, PharmD, MPH, BCPS, BCNSP; and Jason A. Egge, PharmD, MS, BCPS
A review of national Veterans Health Administration data has identified how the number of glucose-lowering agents used prior to insulin initiation impacts glycemic control.

ABSTRACT

Objectives: Nine classes of glucose-lowering agents (GLAs) are available for patients with type 2 diabetes prior to starting insulin. This study’s aim was to determine if the number of GLAs is associated with a difference in glycated hemoglobin (A1C) at insulin initiation in the US Department of Veterans Affairs Health Care System (VAHCS).

Study Design: Retrospective cohort study.

Methods: A retrospective cohort with national Veterans Health Administration data was created. Veterans with type 2 diabetes and first insulin prescription filled in the VAHCS between January 1, 2009, and August 28, 2013, were identified. Included veterans refilled insulin within the first year, had an A1C >7% (53 mmol/mol) at least 60 days prior to insulin initiation, and received a GLA within 6 months prior to insulin. Veterans were grouped into 4 cohorts according to the number of GLAs used.

Results: A total of 90,497 veterans with type 2 diabetes met inclusion criteria. Insulin was initiated at a mean A1C of 9.9% (85 mmol/mol). The mean A1Cs prior to insulin for 1, 2, 3, or >3 GLAs were 10.3% (89 mmol/mol), 9.9% (85 mmol/mol), 9.6% (81 mmol/mol), and 9.6% (81 mmol/mol), respectively. Months to insulin increased with the number of GLA trials and prolonged the time veterans were exposed to A1C >8% (64 mmol/mol).

Conclusions: Multiple glucose-lowering drug classes are associated with a numerical, but not a clinical, difference in A1C at insulin initiation in the closed formulary of the VAHCS. 

Am J Manag Care. 2016;22(4):e134-e140

Take-Away Points

In 2014, it was estimated that more than 29 million Americans had type 2 diabetes, and the estimated total cost for diabetes in the United States was $245 billion in 2012. Diabetes-related costs can decline by 4.2% for each percentage point reduction in glycated hemoglobin (A1C). In our study, initiating insulin after 1 or 2 glucose-lowering agents (GLAs) reduced A1C by 2.5 percentage points in approximately 14 months.
  • Guidelines recommend intensifying patients’ diabetes regimens to achieve A1C goals.
  • A closed formulary resulted in two-thirds of patients starting insulin after trials on 1 or 2 GLAs.
  • Trials of 3 or more GLAs further delayed insulin initiation and prolonged hyperglycemia.
According to the CDC, more than 29 million Americans are currently diagnosed with diabetes, with the projected lifetime risk of developing the disease near 40%.1 The prevalence of diabetes in the veteran population is estimated at 25% for a variety of reasons, including older average age and previous exposure to Agent Orange during the Vietnam era.2 More than 85% of Americans with diabetes are prescribed a glucose-lowering agent (GLA), with the majority using noninsulin therapy.1

Medical costs associated with diabetes are staggering and create a financial burden on the healthcare system.3 In 2012, the estimated total cost of diabetes in the United States was $245 billion, with direct medical expenses responsible for more than 70% of the total. In the United States, more than 60% of the cost for diabetes care is provided by the government (including Medicare, Medicaid, and the military), with the majority of costs secondary to hospitalizations from diabetes-related complications. Given the increased prevalence and progressive nature of diabetes, this cost burden will likely continue to rise.3

The progressive nature of type 2 diabetes (T2D) requires prescribers to modify, and often intensify, diabetes regimens over time.4 Metformin is recommended as the initial GLA for most patients with T2D, but evidence to guide treatment after metformin monotherapy is limited.4 There are currently 9 different classes of GLAs that healthcare providers can prescribe prior to starting insulin (Table 1). The Veterans Affairs (VA)/Department of Defense (DoD) Clinical Practice Guidelines for Management of Diabetes (last published in 2010) and the American Diabetes Association (ADA) Standards of Medical Care in Diabetes contain algorithms to guide providers in making treatment decisions.4,5 In the VA/DoD guidelines, metformin with a sulfonylurea is the preferred oral combination when monotherapy no longer provides adequate glycemic control.5 Alternative agents can be considered for patients unable to use metformin or a sulfonylurea. The Veterans Administration Health Care System (VAHCS) restricts the use of alternative agents by placing them in a nonformulary status with criteria for use.5 With their highest level of evidence, the ADA Standards of Medical Care supports the addition of a second oral agent, a glucagon-like peptide 1 (GLP-1) receptor agonist, or insulin if metformin alone does not achieve or maintain the glycated hemoglobin (A1C) target.

The VA/DoD and ADA standards encourage providers to consider the needs of individual patients when determining appropriate therapy, recognizing the lack of evidence for the “one size fits all” approach.4,5 Glycemic control targets should be determined based on individual patient characteristics in the context of comorbidities, life expectancy, risk of hypoglycemia, pre-existing microvascular complications, and patient preferences.4,5

According to the VA/DoD guidelines, all patients with diabetes should have a target A1C <9% (75 mmol/mol).5 Patients with advanced microvascular disease, major comorbid illness, and/or life expectancy less than 5 years should have a target A1C 8% to 9% (64-75 mmol/mol). Patients who have had diabetes for more than 10 years, and/or have comorbid conditions, and have a combination diabetes regimen including insulin should have a target A1C <8% (64 mmol/mol). A patient without significant microvascular complications, who is free of major concurrent illnesses and has a life expectancy of at least 10 years, should have a target A1C <7% (53 mmol/mol).

In 2012, the ADA and the American Geriatric Society (AGS) published a consensus report on diabetes in older adults.6 Their report creates a framework for establishing glycemic goals in adults with diabetes aged over 65 years. This framework, similar to that of the VA/DoD, considers patient characteristics, health status, life expectancy, hypoglycemia vulnerability, and fall risk.6 Establishing a target A1C does not restrict patients and providers from discussing the benefits of a lower goal, but implies there are reduced benefits of intensifying treatment.5

The addition of insulin is an effective method for lowering A1C. The ADA recognizes that the progressive nature of T2D eventually results in the need for insulin therapy for many patients.4 Evidence supports early insulin initiation, or intensification in patients with significant hyperglycemia (defined by plasma blood glucose >300 mg/dL, A1C >10% [86 mmol/mol], and/or symptoms of hyperglycemia), although treatment with insulin is often delayed.7

The purpose of this retrospective study was to determine if the addition of multiple glucose-lowering drug classes is associated with a difference in A1C at insulin initiation in the closed formulary of the VAHCS.

METHODS
Data Source

The electronic VA Informatics and Computing Infrastructure national database was utilized for data extraction. The study was approved by the University of Iowa Institutional Review Board and the Iowa City VA Health Care System Research and Development Committee. Age and region were determined on the day insulin was initiated, and body mass index (BMI) was calculated using the height and weight closest to the insulin initiation date.

Patient Selection

The study population included veterans with T2D (determined according to International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] codes) who had their insulin prescription first filled in the VA system between January 1, 2009, and August 28, 2013. Data were analyzed for veterans who refilled their insulin prescriptions within the first year, had an A1C >7% (53 mmol/mol) within 60 days prior to insulin initiation, and received a prescription for a GLA within 6 months prior to insulin initiation.

Patient Assignment

Veterans were grouped into 4 cohorts according to the number of glucose-lowering classes used prior to insulin (1, 2, 3, or >3 classes). Each ingredient in a combination medication was counted; for example, Janumet (metformin/sitagliptin) was considered as 2 GLA classes.

Outcomes

The primary outcome measure was A1C at insulin initiation. Secondary outcomes included: months from first prescription of a GLA to insulin initiation, lowest A1C after insulin initiation, and consecutive months of poor glycemic control (defined as an A1C >8% [64 mmol/mol]) prior to insulin initiation. The definition of poor glycemic control was based on VA/DoD and ADA/AGS recommendations for determining A1C target range. According to the US Census Bureau, in 2010 more than 42% of veterans were aged 65 years or older, so we therefore decided that a greater number of veterans with T2D would meet the criteria for an A1C target <8% (64 mmol/mol) compared with <9% (75 mmol/mol) or <7% (53 mmol/mol).8

Statistical Methods

Baseline characteristics for veterans at initiation of insulin following trials of the GLAs were reported as the mean and SD. Descriptive statistics were performed for all outcome variables. To reduce potential bias from extreme values, BMI and lowest A1C post insulin were winsorized at the 99% level in calculating the mean (ie, BMIs below the 1st percentile were set to equal to the 1st percentile BMI, and BMIs above the 99th percentile were set to equal to the 99th percentile). All data were analyzed using SPSS, version 21 (IBM, Armonk, New York).

RESULTS
There were 90,497 veterans with T2D who met the inclusion criteria. Table 2 describes their demographic characteristics along with GLA classes, type of insulin initiated, and final A1C post insulin for the overall population and each cohort. Most veterans in this study were white males; the mean age was 62.8 years. The mean BMI was 32.9, which matches World Health Organization Obesity Class I. Most veterans included in the study population lived in the South (37%), and the least number of veterans lived in the Northeast (14%).

The number of veterans receiving 1, 2, 3, or >3 GLAs was 10,728, 49,860, 23,747, and 5380, respectively. More than 55% of the study population received a trial of 2 GLAs and 26% received a trial of 3 GLAs before starting insulin. Veterans receiving 3 or more GLAs were, on average, 2 to 3 years older than those receiving 2 or less. Nearly 75% of veterans aged under 60 years started insulin after a trial of 1 or 2 GLAs, while about 35% of veterans 60 years or older were found to start insulin after a trial of 3 or more GLAs.

Insulin was initiated in the total study population at a mean A1C—the most recent measurement within 60 days before starting insulin—of 9.9% (85 mmol/mol). Veterans with only 1 GLA trial started insulin with the highest mean A1C at 10.3% (89 mmol/mol) while veterans receiving trials of 3 or more GLAs started insulin with the lowest A1C at 9.6% (81 mmol/mol). The majority of veterans received 2 GLA trials and started insulin with a mean A1C of 9.9% (85 mmol/mol).

Most veterans were started on a basal-only insulin regimen. However, veterans receiving 1 GLA trial were more likely to initiate bolus, or a combination of basal and bolus insulin, compared with the other 3 cohorts. Months from the first GLA prescription to insulin initiation increased with the number of GLA trials and prolonged the time veterans were exposed to A1C >8% (64 mmol/mol) (Figures 1 and 2).

Veterans who received 1 GLA trial started insulin after a mean of 28 months. On average, their A1C was >8% (64 mmol/mol) for 5 months prior to starting insulin. Time to insulin from first GLA prescription increased considerably—to a mean of 60 months—for veterans who received 2 GLAs. The A1C in these veterans was >8% (64 mmol/mol) for 11 consecutive months prior to insulin initiation. After 84 months, veterans in the 3-GLA cohort started insulin, but an additional 10 months lapsed before veterans in the >3-GLA cohort were started. For veterans receiving 3 or >3 GLAs, their A1C was >8% (64 mmol/mol) for 14 and 15 consecutive months, respectively, prior to insulin initiation. In all study patients, the addition of insulin improved the A1C to its lowest value of 7.4% (57 mmol/mol) in 14.5 months. However, it took an additional month to reach the lowest value in veterans with >3 trials of GLAs.

 
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