Table 2.
The Impact of Medicare Part D on Likelihood of Use among Those with Hypertension Diagnosis in 2003
| 2-Year Part D Effect† | ||||||
|---|---|---|---|---|---|---|
| Unadjusted Likelihood of Use* | Propensity Score Weighting | Multivariate Regression | ||||
| Pre | Post | Odds Ratio | (95% CI) | Odds Ratio | (95% CI) | |
| Panel A: Likelihood of use | ||||||
| Any antihypertensive medications | ||||||
| Comparison | ||||||
| No cap | 88.1 | 89.1 | Reference | Reference | ||
| Intervention groups | ||||||
| No coverage | 59.8 | 69.7 | 1.40 | (1.25,1.56) | 1.43 | (1.27,1.6) |
| U.S.$150 cap | 82.2 | 84.6 | 1.08 | (0.95,1.23) | 1.07 | (0.94,1.23) |
| U.S.$350 cap | 86.1 | 86.9 | 0.97 | (0.89,1.05) | 0.97 | (0.9,1.05) |
| ACE | ||||||
| Comparison | ||||||
| No cap | 29.5 | 28.5 | Reference | Reference | ||
| Intervention groups | ||||||
| No coverage | 16.7 | 20.3 | 1.34 | (1.20,1.49) | 1.33 | (1.2,1.48) |
| U.S.$150 cap | 25.9 | 26.4 | 1.08 | (0.98,1.18) | 1.09 | (0.99,1.19) |
| U.S.$350 cap | 29.1 | 29.1 | 1.05 | (1.00,1.10) | 1.05 | (1,1.11) |
| ARB | ||||||
| Comparison | ||||||
| No cap | 27.7 | 29.8 | Reference | Reference | ||
| Intervention groups | ||||||
| No coverage | 10.9 | 17.3 | 1.53 | (1.35,1.75) | 1.52 | (1.34,1.72) |
| U.S.$150 cap | 19.4 | 22.0 | 1.05 | (0.96,1.15) | 1.06 | (0.96,1.16) |
| U.S.$350 cap | 24.7 | 26.6 | 0.99 | (0.95,1.04) | 1 | (0.95,1.04) |
| CCB | ||||||
| Comparison | ||||||
| No cap | 31.9 | 32.9 | Reference | Reference | ||
| Intervention groups | ||||||
| No coverage | 18.7 | 22.6 | 1.21 | (1.10,1.33) | 1.19 | (1.09,1.31) |
| U.S.$150 cap | 28.4 | 29.7 | 1.02 | (0.94,1.11) | 1.03 | (0.95,1.12) |
| U.S.$350 cap | 29.8 | 31.5 | 1.03 | (0.98,1.08) | 1.03 | (0.98,1.08) |
| β-blockers | ||||||
| Comparison | ||||||
| No cap | 41.5 | 45.5 | Reference | Reference | ||
| Intervention groups | ||||||
| No coverage | 23.6 | 34.3 | 1.44 | (1.30,1.59) | 1.45 | (1.32,1.6) |
| U.S.$150 cap | 34.9 | 41.5 | 1.13 | (1.04,1.22) | 1.14 | (1.05,1.23) |
| U.S.$350 cap | 38.1 | 43.6 | 1.07 | (1.02,1.12) | 1.08 | (1.03,1.13) |
| Diuretics | ||||||
| Comparison | ||||||
| No cap | 37.8 | 39.8 | Reference | Reference | ||
| Intervention groups | ||||||
| No coverage | 26.0 | 33.8 | 1.34 | (1.21,1.47) | 1.38 | (1.25,1.53) |
| U.S.$150 cap | 36.1 | 39.7 | 1.07 | (0.98,1.17) | 1.08 | (0.98,1.18) |
| U.S.$350 cap | 36.4 | 38.4 | 1.00 | (0.95,1.06) | 1.01 | (0.96,1.06) |
| 2-year Part D Effect† | ||||||
|---|---|---|---|---|---|---|
| Unadjusted* | Propensity Score Weighting | Multivariate Regression | ||||
| Pre | Post | Estimate | (95% CI) | Estimate | (95% CI) | |
| Panel B: Average daily counts | ||||||
| Any antihypertensive medications | ||||||
| Comparison | ||||||
| No cap | 1.53 | 1.66 | Reference | Reference | ||
| Intervention groups | ||||||
| No coverage | 0.75 | 1.18 | 0.29 | (0.24,0.33) | 0.30 | (0.26,0.34) |
| U.S.$150 cap | 1.27 | 1.46 | 0.05 | (0.01,0.08) | 0.06 | (0.02,0.09) |
| U.S.$350 cap | 1.38 | 1.51 | 0.00 | (−0.02,0.02) | 0.00 | (−0.02,0.02) |
Pre- and postcomparisons are unadjusted raw numbers.
“2-year Part D Effects” are adjusted difference-in-difference estimates from GEE regression models, which measured changes in likelihood of use 2 years pre- and 2 years post-Part D in each intervention group, relative to the changes in outcomes in the comparison group. One set of results were models with propensity score weighting, and the other set of results were from multivariate regressions without propensity score weighting. In calculating propensity score, the following variables were included in the logistic regression: zip-code level of income, race, residing in the urban areas, and individual-level variables such as age categories, sex, and 2004 and 2005 risk scores. Then an inverse weight was applied for each individual in the analytic GEE models. In the multivariate regression, shown for comparison, the above variables used to calculate propensity score were included in the model as covariates.
ACE, angiotensin-converting enzyme; ARB, angiotensin-II receptor blocker; CCB, calcium channel blocker; CI, confidence interval; GEE, general estimating equations.