Colorado's $100 copay cap improves diabetes medication adherence and health outcomes

By Pooja Toshniwal PahariaReviewed by Danielle Ellis, B.Sc.Aug 19 2024

In a recent study published in JAMA Network Open, researchers examined the relationship between Colorado's $100 copayment maximum and self-expenditure, medication compliance, and health service usage for diabetes-associated comorbidities.

Background

Diabetes is the most expensive chronic ailment in the United States, and type 1 disease needs lifetime insulin therapy. Insulin costs have plateaued despite manufacturer cuts, but list prices are ten times higher than in most other nations. This economic burden has resulted in 25 states and the District of Columbia passing legislation reducing insulin copayments for state-regulated commercial health insurance plans. Colorado was the first state to impose an insulin copayment limit, although empirical research on the association between these policies and health outcomes is scarce.

About the study

In the present study, researchers evaluated the impact of the statewide $100 insulin copayment capping policy from Colorado's Insulin Affordability Program on self-expenditure, treatment compliance, and the use of healthcare services for diabetes complications.

Approximately 38 million individuals have diabetes, and more than 7 million use 1 or more formulations of insulin

The study exposure included enrollment in state-regulated health insurance policies abiding by the insulin copayment cap law enacted on January 1, 2020. The primary outcome measures were basal and bolus insulin adherence, self-expenditure, and healthcare usage for diabetes-related comorbidities.

Researchers used the proportion of days covered measure to assess adherence to basal and bolus treatment; expenditure by self, based on the prescription cost for a 30-day supply; and identified healthcare service use for diabetes-associated complications using primary diagnosis codes from medical claim data.

From January 2019 to December 2020, researchers analyzed non-elderly individuals with insulin-dependent diabetes using Colorado's All-Payer Claims Database (CO APCD). Eligible individuals were under 65 years old and engaged in the same healthcare plan between January 2018 and December 2020.

The researchers identified medical claims for diabetes-associated complications (e.g., hyperglycemia, hypoglycemia, ketoacidosis, tissue or skin infections, retinopathy, cardiovascular illnesses, and renal problems) using primary diagnostic codes aggregated at the individual-month level. They monitored the participants for two years (January 2019–December 2020).

The post-policy implementation phase lasted between January and December 2020. The researchers utilized difference-in-differences regressions to examine outcome changes pre- and post-policy implementation among individuals continually enrolled in non-state and state-regulated insurance plans. They performed subgroup analyses depending on individuals' pre-policy expenditure (low: never spent $100.0 by self; high: $100 paid by self, one or more times).

Researchers analyzed data between June 2023 and May 2024 using generalized linear regressions, adjusting for age, gender, domicile, comorbidities, insurance plan type, and non-diabetes-related medical claims. To corroborate the findings, they performed sensitivity analyses, excluding two months preceding and following policy implementation, and falsification tests by repeating regressions using prescriptions apart from insulin as study outcomes.

Results

The study included 1,629 insulin-dependent diabetic patients, with 924 males (57%), 540 having comorbidities (33%), and an average age of 41 years. Among the participants, 123 (7.60%) registered in HDHPs, with 21% filing medical claims for diabetes-associated complications. One in every four insulin users spent more than $100 from their pocket for their prescriptions. Initially, the mean self-expenditure for a one-month supply of basal insulins was $68, and bolus insulins were $88. The treatment adherence rate was 63% for basal insulins and 65% for bolus insulin.

The copayment capping policy resulted in $17 in self-expense savings for basal insulin and $12 for bolus insulin doses, as well as 3.20% and 3.30% gains in adherence, respectively. Adherence changes were related to increases in the pre-policy high-spending individuals (basal, 9.9%; bolus, 13%). The program led to a 30% reduction in the mean number of insurance claims for type 1 diabetes-associated complications per individual monthly in the high-spender group. Sensitivity analyses found comparable results, and falsification analysis using noninsulin prescriptions had statistically negligible outcomes, validating the study findings.

Self-expenditure for bolus and basal insulins was highest between January and February and lowest in the last three months, corresponding to when participants reached their maximums or deductibles. However, in January 2020, the policy implementation month, spending from pockets was reduced, and seasonal fluctuation was reduced, notably for basal insulins. The drop was more severe among people who paid above $100 by themselves one or more times before policy implementation.

Conclusion

The study showed that enforcing insulin limits on type 1 diabetic patients lowered out-of-pocket costs while improving treatment adherence and health outcomes. However, these gains primarily benefited individuals whose pre-policy expenditure levels were above the ceiling. The cap level determines the short-term consequences.

The findings support policymakers' aims to make insulin more inexpensive, thus boosting insulin-dependent people's access to and adherence to therapy. In January 2022, legislation changed to restrict self-expenditure to $100 for a one-month supply and to offer emergency prescriptions to qualified persons for a fee of no more than $35 within 12 months.