Use and Out-of-Pocket Costs of Insulin for Type 2 Diabetes Mellitus From 2000 Through 2010

Insulin analogs are molecularly altered forms of insulin. Compared with human synthetic and animal insulin for treatment of type 2 diabetes, short-acting analogs may offer flexible dosing and convenience, long-acting analogs less nocturnal hypoglycemia,¹ but both at greater cost.² Because insulin analogs have become increasingly popular,^3,4 we examined trends in insulin use, out-of-pocket expenditures, and severe hypoglycemic events among privately insured US adults with type 2 diabetes from 2000 through 2010.

We conducted a retrospective analysis of data from the Optum Labs Data Warehouse, an administrative claims database of privately insured enrollees from throughout the United States, but with more representation from states in the South and Midwest. The study was exempt from institutional review board approval because it used preexisting, deidentified data. Adults aged 18 years or older with type 2 diabetes and at least 2 years of continuous plan enrollment between January 2000 and September 2010 were included.

We defined diabetes according to the Health Plan Employer Data and Information Set criteria and excluded patients with claims for type 1 diabetes in the absence of oral antihyperglycemic medications. First, we calculated the proportion of patients with type 2 diabetes who used any insulin during each year and characterized patients with insulin use through descriptive analyses. Second, we calculated the proportion of patients who obtained each specific insulin type using the Cochran-Armitage test to assess for trends in insulin use. Third, we calculated median out-of-pocket costs associated with each insulin prescription per year (adjusted to 2010 dollars⁵), comparing costs across years using quantile regression. In addition, among patients with insulin use, we examined age- and sex-adjusted rates of severe hypoglycemic events (hospitalization or emergency department visit with a primary discharge diagnosis of hypoglycemia).⁶

For all analyses, a 2-sided P value of less than .05 was considered significant. All analyses were performed using SAS statistical software version 9.2 (SAS Institute Inc).

From 2000 through 2010, 123 486 patients filled at least 1 prescription for insulin, comprising 9.7% (95% CI, 9.5%-9.8%) of adults with type 2 diabetes in 2000 and 15.1% (95% CI, 15.0%-15.3%) in 2010 (P = .001). Characteristics of the study sample appear in the Table. Among adults who used insulin, 96.4% (95% CI, 96.0%-96.8%) filled prescriptions for human synthetic insulin in 2000 and 14.8% (95% CI, 14.5%-15.2%) in 2010 (P < .001), whereas 18.9% (95% CI, 18.2%-19.7%) filled prescriptions for insulin analogs in 2000 and 91.5% (95% CI, 91.2%-91.8%) in 2010 (P < .001) (Figure). Use of animal insulin was less than 1% during all years.

The median out-of-pocket costs per prescription for all types of insulin increased from $19 (interquartile range, $14-$23) in 2000 to $36 (interquartile range, $20-$53) in 2010 (P < .001). A small, nonstatistically significant decline in the rate of severe hypoglycemic events among insulin users was observed (21.1 and 17.7 events per 1000 person-years in 2000 and 2010, respectively, P = .054).

Among privately insured adults in the United States, use of insulin among patients with type 2 diabetes increased from 10% in 2000 to 15% in 2010 in the context of widespread adoption of insulin analogs. Out-of-pocket expenditures increased from a median of $19 to $36. Severe hypoglycemic events declined slightly but this was not statistically significant.

Our study has some limitations. First, we included privately insured patients only; public health care systems may use insulin analogs to a lesser extent. Second, we had no information for total expenditures on insulin and may have underestimated the total cost to the health care system. Third, we could not account for the use or cost of insulin delivery devices (except for prefilled pens). Fourth, we could not identify hypoglycemic events that did not require medical assistance. Although we found a nonsignificant decline in severe hypoglycemia, our analyses may be underpowered and we cannot exclude changes in less severe hypoglycemic events. Fifth, we relied on unpublished working documents describing the database, so there may be some uncertainty regarding the accuracy, completeness, and validity of the data.

We found a large increase in the prevalent use of insulin analogs among privately insured patients with type 2 diabetes. The clinical value of this change is unclear.

Corresponding Author: Kasia J. Lipska, MD, MHS, Department of Internal Medicine, Yale School of Medicine, PO Box 208020, New Haven, CT 06520 (kasia.lipska@yale.edu).

Author Contributions: Dr Shah had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Lipska, Ross, Beran, Yudkin, Shah.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Lipska, Beran, Yudkin.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Van Houten, Yudkin, Shah.

Obtained funding: Shah.

Administrative, technical, or material support: Yudkin, Shah.

Study supervision: Yudkin, Shah.

Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Lipska reported receiving support from the Centers for Medicare & Medicaid Services to develop ambulatory care performance measures; being supported by the Pepper Center career development award (P30 AG21342); receiving grant R03 AG045086 (Grants for Early Medical/Surgical Specialists’ Transition to Aging Research) from the National Institute on Aging; and receiving a scholar award (grant UL1 TR000142) through the Yale Center for Clinical Investigation. Dr Ross reported being a member of a scientific advisory board for FAIR Health Inc; receiving grant funding from Pew Charitable Trusts, Medtronic Inc, and Johnson & Johnson; receiving funding from the Centers for Medicare & Medicaid Services to develop and maintain performance measures used for public reporting; receiving funding from the US Food and Drug Administration to develop methods for postmarket surveillance of medical devices; being supported by grant K08 AG032886 from the National Institute on Aging; receiving funding from the American Federation for Aging Research through the Paul B. Beeson career development award program; and receiving personal fees from Pew Charitable Trusts outside the submitted work. Dr Shah reported receiving other from Optum Labs outside the submitted work. No other disclosures were reported.

Funding/Support: This project was supported by grant R21HS17628 from the Agency for Healthcare Research and Quality.

Role of the Sponsor: The Agency for Healthcare Research and Quality had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Additional Contributions: We thank Harlan Krumholz, MD, SM (Department of Medicine, Yale University School of Medicine), and Victor Montori, MD, MSc (Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic), for their valuable comments on an earlier draft. No compensation was received.