OP2-2 - Impact of Myocardial Infarction on Statin Adherence among Medicaid Beneficiaries in 14 States from 2001 to 2015

Monday, April 24, 2023

4:15 PM – 5:45 PM GMT

Presenting Author(s)

CJ

Courtney A. Johnson, MPH (she/her/hers)

PhD Candidate
Brown University, United States

Author(s)

TS

Theresa I. Shireman, PhD (she/her/hers)

Director Center for Gerontology & Health Care Research, Professor Health Services, Policy, &Practice
Brown University
Providence, RI, United States
AT

Amal N. Trivedi, MD, MPH

Professor of Health Services, Policy & Practice, Professor of Medicine
Brown University
Providence, RI, United States
OG

Omar Galárraga, PhD (he/him/his)

Director of PhD Program in Health Services, Policy & Practice (HSPP), Associate Professor of HSPP
Brown University
Providence, RI, United States

ABSTRACT:

Background: Medicaid beneficiaries, who are low-income and have high chronic disease burdens, face many economic and social barriers to obtaining consistent healthcare. While research has found that medication adherence is suboptimal among this population, there is limited work on how a chronic disease-related ‘health shock’, such as myocardial infarction (MI), impacts adherence. We hypothesize that adherence improves after a health shock, but that this improvement attenuates over time.

Objective: To assess if myocardial infarction (MI) hospitalization, a health shock, impacts statin adherence.

Methods: Adult (18 – 64 years) Medicaid beneficiaries who filled at least one statin prescription from 2001 to 2015 were included. Beneficiaries dually eligible for Medicare were excluded since their prescriptions are covered by Medicare after 2006. The ‘health shock’ cohort was beneficiaries with a MI inpatient claim (ICD-9-CM: 410, ICD-10-CM: I21) while Medicaid eligible. Beneficiaries without the health shock were assigned a ‘proxy’ MI date; the time difference between Medicaid enrollment and MI date in the health shock cohort was randomly assigned to comparison cohort beneficiaries, and proxy MI date calculated as ‘Medicaid enrollment date’ plus ‘time difference’.

Adherence was measured using proportion of days covered (PDC), calculated as days of medication supplied in a month divided by days in the month. Pre-PDC was measured for the 12 months pre-MI. Post-PDC measurement started after hospital discharge for the health shock cohort and after proxy MI date for the comparison cohort, with censoring at subsequent MI, loss of Medicaid enrollment, or death. We used a differences-in-differences approach to compare changes in PDC in the health shock versus comparison cohort, before and after MI. Models were adjusted for demographic, geographic, and clinical characteristics, with robust standard errors clustered at the patient level.

Results: The health shock cohort had 53,103 beneficiaries and the comparison cohort 912,789. The health shock cohort was older (mean age: 54.1 [SD 7.5] vs 50.5 [SD 9.4]), and was more likely to be white (45.6% vs 41.9%) and male (50.7% vs 41.7%) than the comparison cohort (p < 0.01, all characteristics). Mean pre-PDC was 49.1% in the health shock cohort and 50.9% in the comparison cohort. Post-health shock, the adjusted difference-in-difference PDC was 11.9 percentage points (pp) (99% CI: 11.5, 12.4), implying a 23.4% relative change due to the health shock (i.e., 11.9/50.9). The adjusted difference-in-difference PDC decreased from 12.9 pp (99% CI: 12.4, 13.4) in the first 3 months post-health shock to 10.9 pp (99% CI: 10.4, 11.6) in the 9 to 12 months post-health shock, suggesting an attenuation of the health shock’s impact on adherence.

Conclusions: A health shock in the form of a myocardial infarction greatly impacted statin adherence, increasing PDC by over 23%. Post-MI, the health shock cohort had consistently higher PDC than the comparison cohort, although PDC decreased over follow-up in both cohorts. The health shock may have increased adherence by changing perceptions of long-term health or was a ‘teachable moment’ for better medication taking behavior. These results may help identify post-hospitalization windows for medication adherence interventions.