TABLE 5.

Difference-in-Differences Analysis Examining Changes in Prescription Drug Use and Plan Costs Between the Study Group Members^a

	Utilization β (95% CI)	P Value	Plan Costs β (95% CI)	P Value
All drugs	-0.06 (-0.12, -0.01)	0.020	0.27 (0.10, 0.45)	0.002
Generic drugs	-0.09 (-0.15, -0.04)	0.001	-0.09 (-0.21, 0.03)	0.126
Brand drugs	0.27 (0.11, 0.42)	< 0.001	0.85 (0.50, 1.19)	< 0.001

^aEach drug use and plan cost outcomes measure was analyzed in a separate generalized linear regression model with the interaction between study group and time period as the main independent variable of interest. All regression models were adjusted for age, gender, 2-level GPI count (disease burden proxy), and median household income. Numbers in bold indicate statistical significance at P < 0.05.

β = beta coefficient; CI = confidence interval; GPI = Generic Product Identifier.