Patterns of prescription drug expenditures and medication adherence among medicare part D beneficiaries with and without the low-income supplement

Table 3 Regression-adjusted estimates of expenditures, prescription drug use, and adherence to medications stratified by type of medicare part D coverage (n = 344,817)

	LIS N = 25,226	Non-LIS/GC N = 29,289	Non-LIS/Non-GC N = 290,302
Expenditures
Total expenditures	$1,887^a,b	$1,360^a	$1,341
Total expenditures	(1,864-1,910)	(1,344-1,375)	(1,336-1,347)
Out-of-pocket expenditures	$148^a,b	$546^a	$570
Out-of-pocket expenditures	(146–150)	(539–552)	(567–572)
Plan expenditures^c	$1,708^a,b	$822^a	$776
Plan expenditures^c	(1,687-1,729)	(811–833)	(772–780)
Expenditures on brand name medications
Total expenditures	$1,325^a,b	$926^a	$898
	(1,305-1,346)	(911–941)	(893–903)
Out-of-pocket expenditures	$96^a,b	$374^a	$369
Out-of-pocket expenditures	(94–98)	(368–381)	(367–371)
Plan expenditures^c	$1,221^a,b	$560^a	$537
Plan expenditures^c	(1,202-1,240)	(549–571)	(533–540)
Expenditures exceeding the gap threshold	27.6%^a,b	17.4%^a	16.9%
Expenditures exceeding the gap threshold	(27.2-28.1)	(17.0-17.8)	(16.8-17.0)
Prescriptions
Total number of prescriptions	38.1^a,b	25.1^a	26.5
Total number of prescriptions	(37.8-38.4)	(24.9-25.3)	(26.4-26.5)
Total number of brand name prescriptions	10.7^a,b	6.4^a	6.9
Total number of brand name prescriptions	(10.5-10.8)	(6.3-6.5)	(6.87-6.92)
Adherence to medications
Diabetes drug adherence	62.5%^a,b	57.7%	57.4%
Diabetes drug adherence	(61.0-63.9)	(56.0-59.4)	(56.9-58.0)
Hypertension drug adherence	65.6%^a,b	64.2%^a	62.4%
Hypertension drug adherence	(64.9-66.3)	(63.5-64.9)	(62.2-62.6)
Lipid-lowering drug adherence	59.6%^a,b	57.0%^a	55.6%
Lipid-lowering drug adherence	(58.5-60.6)	(56.0-58.0)	(55.3-55.9)

LIS: low-income subsidy beneficiaries; GC: gap coverage; PDC, proportion of days covered, which was calculated from dispensing data within each class of drugs; Adherence: defined as having a PDC ≥80% in the year or month for the entire regimen, allowing drug supply to carry over from month to month.
Each model of medication adherence included only beneficiaries with the condition of interest. Estimates were adjusted for the individual beneficiary characteristics and clinical co-morbidities listed in Table 1 and for the residential census characteristics listed in Table 2.
^aSignificantly different from the Non-LIS/Non-GC group (p <0.05).
^bSignificantly different from the Non-LIS/GC group (p <0.05).
^cMeasures of plan cost for LIS beneficiaries is comprised of the cost to the plan plus subsidies.

ISSN: 1472-6963