Table 2.
The Impact of the Coverage Gap on Antidepressant Use among Elderly Beneficiaries Diagnosed with Depression in 2007
| Unadjusted Data* | Diff-in-Diff Coverage Gap Effects† | % Change, Diff-in-Diff Effects/Pre-Gap Values‡ | |||||
|---|---|---|---|---|---|---|---|
|
| |||||||
| Pre-Gap | Within-Gap | Estimate | 95% CI | % | 95% CI | ||
|
Probability of Using an Antidepressant
| |||||||
| All | No-coverage | 0.81 | 0.63 | −0.05 | (−0.06, −0.03) | −5.6 | (−7.1, −4.1) |
| Generic-only | 0.83 | 0.72 | −0.03 | (−0.05, −0.02) | −4.1 | (−5.6, −2.5) | |
| LIS | 0.80 | 0.70 | Reference | ||||
|
| |||||||
| Brand-name | No-coverage | 0.40 | 0.27 | −0.06 | (−0.07, −0.05) | −14.2 | (−16.9, −11.6) |
| Generic-only | 0.37 | 0.27 | −0.04 | (−0.05, −0.03) | −11.0 | (−14.1, −7.8) | |
| LIS | 0.30 | 0.24 | Reference | ||||
|
| |||||||
| Generics | No-coverage | 0.56 | 0.43 | 0.00 | (−0.02, 0.01) | −0.9 | (−3.0, 1.3) |
| Generic-only | 0.62 | 0.55 | −0.01 | (−0.02, 0.01) | −1.3 | (−3.4, 0.8) | |
| LIS | 0.62 | 0.53 | Reference | ||||
|
| |||||||
|
No. of Monthly Prescriptions for Antidepressants
| |||||||
| All | No-coverage | 0.75 | 0.57 | −0.09 | (−0.11, −0.07) | −12.1 | (−14.3, −9.9) |
| Generic-only | 0.86 | 0.71 | −0.06 | (−0.08, −0.04) | −6.9 | (−9.1, −4.8) | |
| LIS | 0.78 | 0.70 | Reference | ||||
|
| |||||||
| Brand-name | No-coverage | 0.29 | 0.19 | −0.07 | (−0.08, −0.06) | −23.6 | (−26.9, −20.3) |
| Generic-only | 0.29 | 0.19 | −0.06 | (−0.07, −0.05) | −20.3 | (−24.0, −16.7) | |
| LIS | 0.22 | 0.19 | Reference | ||||
|
| |||||||
| Generics | No-coverage | 0.46 | 0.38 | −0.02 | (−0.04, −0.01) | −4.9 | (−8.0, −1.8) |
| Generic-only | 0.58 | 0.52 | 0.00 | (−0.02, 0.02) | −0.1 | (−2.9, 2.7) | |
| LIS | 0.56 | 0.51 | Reference | ||||
|
| |||||||
|
Monthly Pharmacy Spending for Antidepressants
| |||||||
| All | No-coverage | 40 | 26 | −8.29 | (−9.38, −7.21) | −20.8 | (−23.5, −18) |
| Generic-only | 44 | 31 | −6.63 | (−7.83, −5.43) | −15.0 | (−17.8, −12.3) | |
| LIS | 35 | 30 | Reference | ||||
|
| |||||||
| Brand-name | No-coverage | 30 | 19 | −7.98 | (−9.02, −6.95) | −27.0 | (−30.5, −23.5) |
| Generic-only | 30 | 19 | −7.05 | (−8.22, −5.88) | −23.4 | (−27.3, −19.5) | |
| LIS | 21 | 19 | Reference | ||||
|
| |||||||
| Generics | No-coverage | 10 | 7 | −0.31 | (−0.76, 0.14) | −3.0 | (−7.3, 1.3) |
| Generic-only | 14 | 11 | 0.42 | (−0.15, 0.99) | 3.0 | (−1.1, 7.1) | |
| LIS | 14 | 11 | Reference | ||||
*
These are average numbers in the pre-gap and within-gap periods, but they are unadjusted raw data.
†
“Diff-in-Diff Coverage Gap Effects” are adjusted estimates from the difference-in-difference model with the inverse of propensity score as a weight. The estimates measure changes in outcomes between within-gap and pre-gap periods in each study group, relative to the changes in outcomes in the comparison group (“Reference”).
‡
“% Change” is calculated using “Diff-in-Diff Coverage Gap Effects” divided by pre-gap values. Abbreviations: LIS = low-income-subsidies; this is the comparison group.