Among all 303,978 beneficiaries who reached the coverage gap in 2006 or 2007, 94,220 (31%) were enrolled in Part D plans while the remainder were enrolled in non-Part D retiree plans. Among enrollees in Part D plans, 9,436 (10%) received no financial assistance to pay for drugs during the coverage gap (). At least 79% had hypertension, and ≥35% had coronary artery disease. In the Early Part D cohort, 38% of non-subsidy enrollees had diabetes compared to 50% of full subsidy beneficiaries. Among retirees, 35% had coronary artery disease compared to 40% of non-subsidy enrollees. In the 2 months prior to cohort entry in 2006, non-subsidy beneficiaries used an average of 6 drugs, whereas partial subsidy beneficiaries used an average of 7 and full subsidy beneficiaries an average of 8. All beneficiaries reached the gap spending threshold late in the year. Non-enrollees reached the threshold last, after 229–240 days (~8 months).
Baseline characteristics of all 303,978 Medicare beneficiaries who reached the coverage gap spending threshold in 2006 or 2007.
The PS model had a c statistic of 0.72. Of the 9,436 exposed beneficiaries, 9,383 (99%) could be PS-matched. The hdPS model had an improved c statistic of 0.91; still, nearly all exposed patients, 9210 (98%), could be hdPS-matched. After PS-matching, measured covariate distributions were largely balanced between the exposed and unexposed groups (), and residual differences were minimal: for example, unexposed matched beneficiaries had $123 more Medicare Parts A and B spending in the baseline year than did exposed beneficiaries. hdPS-matched results were similar (data not shown).
Selected baseline characteristics* of multivariate propensity score 1:1 matched beneficiaries in the Early Part D cohort, 2006 and the Established Part D cohort, 2007.
Kaplan-Meier curves demonstrated the almost immediate difference in drug discontinuation rates after coverage gap entry (). Beneficiaries spent a median 95 days (IQR: 49, 145) in the coverage gap, with exposed beneficiaries having discontinued 10.1% (IQR: 4.8%, 13.5%) of drugs by day 95, whereas unexposed had discontinued 6.1% (IQR: 2.8%, 8.8%).
Survival function estimates: drug discontinuation since reaching the coverage gap spending threshold
In the PS-matched pooled cohort, the exposed death rate was 25% greater than that of the unexposed, 5 versus 4 deaths/100 person-years (). Among the exposed, 73% of deaths occurred outside the hospital, whereas among the unexposed, 74% of deaths occurred outside the hospital. Exposed patients were 20% more likely to have hospitalizations for MI or stroke or to die than were the unexposed. In the hdPS-matched pooled cohort, differences in event rates for this outcome disappeared. Similarly, in the hdPS-matched cohort, the exposed death rate was no greater than that of the unexposed and exposed patients were no more likely to die outside of a hospital setting than were unexposed patients (73% versus 68%, p=0.31).
Table 3 Number and rates of health services utilization and cardiovascular outcome events in the coverage gap period among beneficiaries who received no financial assistance (exposed) compared with beneficiaries who received financial assistance (unexposed) in (more ...)
In PS-matched analyses, exposed beneficiaries had elevated but non-significant increased hazards of death (HR=1.25, 95% CI, 0.98–1.59) (). Hazard ratios were nearly identical when location of death was considered: out-of-hospital death (HR=1.25, 0.94–1.65). Exposed beneficiaries were 28% more likely to die or have a hospitalization for MI or stroke (1.02–1.60) but no more or less likely than unexposed beneficiaries to have increased rates of non-discretionary hospitalizations (hospitalizations occurring within 24 hours of an emergency room visit, HR=0.65, 0.41–1.03) or emergency room visits (HR=0.87, 0.74–1.02) with cardiovascular diagnoses. In hdPS-matched analyses, the hazard of all cause death remained non-significant (HR=0.99, 0.78–1.24) as did the hazard of out-of-hospital death (HR=1.07, 0.81–1.41). In contrast to PS-matched results, in the hdPS-matched analysis, exposed beneficiaries were no more or less likely to die or have a hospitalization for MI or stroke (HR=1.04, 0.84–1.30). None of the analyses showed effect modification by pre-August versus August and after arrival to the spending threshold.
Hazard ratios of adverse health events in the coverage gap, comparing beneficiaries who received no financial assistance (exposed) with beneficiaries who received financial assistance (unexposed) in the coverage gap.
The separate sensitivity analyses which 1) excluded exposed beneficiaries with generic drug coverage during the coverage gap period, 2) limited the unexposed group to retirees only (excluded low-income beneficiaries with full or partial subsidies), 3) explored alternate covariate assessment periods, or 4) used only the primary diagnosis code for cardiovascular outcomes all produced analogous results.