Objectives: This research investigates the relationship between income, age, and the utilization of prescription drugs to determine variation by income levels and age group.
Methods: Data derived from a random sample of approximately 6 million commercially insured members whose pharmacy benefits are managed by a large pharmacy benefit manager were used. The sample included all adjudicated claims and basic demographic information for the period 2010-2012 combined with median income data at the Zip Code level based on Zip Code Tabulation Area data from the US Census Bureau (Five Year Sample of the American Community Survey). The outcome measure was annual average days’ supply of prescription medications. Least Squares Means Estimates of annual days supply by income decile were adjusted by member age group. Median income ranged from about $32,000 to $104,000 and the age groups were defined as 0-19, 20-34, 35-49, 50-64 and 65+(Non-Part D active or retired).
Results: The overall growth in average days’ supply of prescription medications varied considerably by income and age. Utilization growth was 1% or less for the top two income deciles and 2.3% and 6.6% for the bottom two deciles respectively in 2011 and 2012. However, utilization for patients under age 35 increased as income increased (34.3% days in 2012). For patients 35 and older utilization decreased as income increased (-7.3% days in 2012).
Conclusions: These results reinforce that for middle aged and older patients, lower income may be correlated with poorer health habits that may cause chronic disease. This is consistent with other published research indicating that health status is positively correlated with income.