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Effects of Health Insurance Benefit Plan Design on Effectiveness of Anti-diabetic Medications in Adults with Type 2 Diabetes Mellitus
Method: We used a retrospective longitudinal cohort study design to look at administrative claims data for both public and private payers in the US from the 2007-2010 Multi-Payer Claims Database (MPCD). Beneficiaries over 18 years of age and having >=2 inpatient or outpatient diagnoses of T2DM (ICD-9-CM codes: 250.x0 or 250.x2) within 12 months were eligible for inclusion in the study cohort. They were also required to have at least 12 month of continuous enrollment before and after the first diagnosis of T2DM, with neither T2DM diagnosis nor anti-diabetic used in the pre-index period. Individuals enrolled in capitated health plans were (exclusively capitation-plan beneficiaries) compared with people covered by at least one Fee for Service (FFS) plan (FFS-plan beneficiaries). Propensity score matching technique (PSM) was used to address the self-selection of health plan coverage. Logistic regression models for the four outcome variables (hospital admission, proportion of days cover (PDC), ACE inhibitors use and statin use) were used to measure the effects of insurance types (FFS versus capitation), controlling for demographics and clinical characteristics.
Results: Among 18,718 individuals who met the eligibility criteria, a quarter of them (n=4466 (24.76%)) were enrolled only in capitated health plans and 13574 (75.24%) were covered by at least one FFS health plan. Overall, 3384 (18.08%) had at least one hospital admission while 40.57% had good medication adherence as measured by PDC≥0.8. The proportion of ACE inhibitors use and statin use were 14.14% and 23.32% respectively. The PSM scores were used to match 3351 beneficiaries of FFS health plans with 3351 beneficiaries of Capitated health plans. All baseline characteristics for the PSM-matched groups were comparable. Coverage of FFS health plan (OR=1.48, 95% confidence interval [CI]= 1.295-1.688), higher Charlson Comorbidity Index Score(CCI), insulin use, comorbid mental disease were significantly associated with increased risk of hospital admission, while residence in the Northeast or West region were associated with lower risk of hospital admission compared with the South (all p<0.05). Medication adherence did not differ by coverage of health plans. Older age and being White were significantly associated with better medication adherence while insulin use was associated with lower medication adherence (all p <0.05). FFS health plan coverage (OR=1.88, 95%CI=1.614-2.188]), Whites, residence in Midwest compared with the South, and insulin use were significantly more likely to use ACE inhibitors while older age was associated with lower odds of ACE Inhibitors use (all p<0.05). We also found that FFS health plan coverage (OR=2.32, 95%CI=2.049-2.638), male, Whites, residence in Northeast compared with the South, and insulin use were significantly associated with higher odds of statins use while older age and higher CCI Score were significantly associated with lower odds of statins use (all p <0.05).
Conclusion: After PSM, FFS health plan coverage is associated with more hospital admissions and use of ACE inhibitors and statins. Understanding the causality relationships between health plans and health outcomes are warranted for effective system-level intervention.