Table 4.
The Impact of Coverage Gap on Oral Anti-diabetic Medication Use and Spending among Elderly Beneficiaries Diagnosed with Depression in 2007
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| Unadjusted Data* | Diff-in-Diff Coverage Gap Effect† | % Change, Diff-in-Diff Effects/Pre-Gap Values‡ | |||||
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| Pre-Gap | Within-Gap | Estimate | 95% CI | % | 95% CI | ||
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Probability of Using a Drug
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| All | No-coverage | 0.15 | 0.12 | −0.01 | (−0.02, −0.01) | −8.7 | (−12.4, −4.9) |
| Generic-only | 0.20 | 0.17 | −0.02 | (−0.03, −0.02) | −11.0 | (−14.5, −7.5) | |
| LIS | 0.22 | 0.19 | Reference | ||||
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| Brand-name | No-coverage | 0.06 | 0.04 | −0.01 | (−0.01, 0.00) | −14.3 | (−22.1, −6.6) |
| Generic-only | 0.08 | 0.05 | −0.01 | (−0.01, 0.00) | −7.4 | (−14.7, −0.1) | |
| LIS | 0.09 | 0.06 | Reference | ||||
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| Generics | No-coverage | 0.13 | 0.10 | −0.01 | (−0.01, 0.00) | −5.6 | (−10.1, −1.1) |
| Generic-only | 0.18 | 0.15 | −0.01 | (−0.02, −0.01) | −8.4 | (−12.5, −4.4) | |
| LIS | 0.19 | 0.17 | Reference | ||||
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No. of Monthly Prescriptions
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| All | No-coverage | 0.17 | 0.12 | −0.02 | (−0.03, −0.01) | −13.4 | (−18.6, −8.2) |
| Generic-only | 0.25 | 0.19 | −0.03 | (−0.04, −0.01) | −10.3 | (−14.6, −6.0) | |
| LIS | 0.25 | 0.21 | Reference | ||||
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| Brand-name | No-coverage | 0.05 | 0.02 | −0.01 | (−0.02, −0.01) | −24.6 | (−33.8, −15.4) |
| Generic-only | 0.06 | 0.03 | −0.01 | (−0.02, −0.01) | −17.5 | (−26.1, −8.9) | |
| LIS | 0.07 | 0.04 | Reference | ||||
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| Generics | No-coverage | 0.12 | 0.10 | −0.01 | (−0.02, 0.00) | −8.9 | (−15.1, −2.7) |
| Generic-only | 0.18 | 0.16 | −0.01 | (−0.02, −0.01) | −7.9 | (−12.8, −3.0) | |
| LIS | 0.19 | 0.17 | Reference | ||||
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Monthly Pharmacy Spending
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| All | No-coverage | 8 | 5 | −1.62 | (−2.28, −0.97) | −19.4 | (−27.1, −11.6) |
| Generic-only | 11 | 7 | −2.05 | (−2.85, −1.25) | −18.1 | (−25.1, −11.0) | |
| LIS | 12 | 9 | Reference | ||||
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| Brand-name | No-coverage | 7 | 4 | −1.47 | (−2.10, −0.83) | −22.0 | (−31.5, −12.5) |
| Generic-only | 9 | 4 | −1.72 | (−2.49, −0.94) | −19.6 | (−28.4, −10.8) | |
| LIS | 9 | 6 | Reference | ||||
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| Generics | No-coverage | 2 | 1 | −0.16 | (−0.29, −0.03) | −9.2 | (−16.5, −1.9) |
| Generic-only | 3 | 2 | −0.33 | (−0.48, −0.18) | −12.8 | (−18.5, −7.2) | |
| LIS | 3 | 2 | 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.