Health Outcome Changes in Individuals With Type 1 Diabetes After a State-Level Insulin Copayment Cap
Authors' conclusion
In this cohort study of Colorado's insulin copayment cap among individuals with type 1 diabetes, the policy was associated with an overall decline in out-of-pocket spending, an increase in medication adherence, and a decline in claims for diabetes-related complications only among insulin users who spent more than $100 in the prepolicy period at least once.
Study context
- Population
- Nonelderly insulin users with T1D continuously enrolled, Colorado, January 2019 to December 2020; mean (SD) age 40.6 (15.9) years, 56.7% male39,096 person-months
- Participants
- 1,629 users
- Exposure
- State-regulated plans subject to $100 insulin copayment cap vs non-state-regulated plans, prepolicy vs postpolicy
- Outcome
- Adherence to basal and bolus insulin (proportion of days covered), out-of-pocket spending for a 30-day supply, and health care utilization for diabetes-related complications
Methodological detailsdifference-in-differences, All-Payer Claims Database
- Difference-in-differences
- All-Payer Claims Database
Main finding
As reported in the abstract
Out-of-pocket spending change, basal insulin
$17.3 decline
95% CI -$27.3 to -$7.3
Out-of-pocket spending change, bolus insulin
$11.5 decline
95% CI -$24.7 to $1.7
Adherence increase, basal insulin
3.2 percentage points
95% CI 0.0 to 6.5
Adherence increase, bolus insulin
3.3 percentage points
95% CI 0.3 to 6.4
Observational data: associations, not effects.
Further findings
Adherence change, prepolicy high-spending subgroup
- Adherence increase, basal insulin
- 9.9 percentage points (95% CI, 2.4 to 17.4)
- Adherence increase, bolus insulin
- 13.0 percentage points (95% CI, 5.1 to 20.9)
Medical claims for diabetes-related complications per person per month, high spenders
- Mean reduction
- −0.09 (95% CI, −0.16 to −0.02); a 30% decrease
Original publication
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