Poverty, Transportation Access, and Medication Nonadherence

Abstract

Background and objectives: Variability in primary medication nonadherence (PMN), or failure to fill a new prescription, influences disparities and widens equity gaps. This study sought to evaluate PMN across 1 metropolitan area and assess relationships with underlying zip code-level measures.

Methods: This was a retrospective observational study using data extracted from 1 regional community pharmacy market-share leader (October 2016-April 2017). Data included patient age, sex, payer, medication type, and home zip code. This zip code was connected to US census measures enumerating poverty and vehicle access, which were treated as continuous variables and within quintiles. The prescription-level outcome was whether prescriptions were not filled within 30 days of reaching the pharmacy. The ecological-level outcome was PMN calculated for each zip code (numerator, unfilled prescriptions; denominator, received prescriptions).

Results: There were 213 719 prescriptions received by 54 included pharmacies; 12.2% were unfilled. Older children, boys, and those with public insurance were more likely to have prescriptions not filled. Prescriptions originating from the highest poverty quintile were significantly more likely to not be filled than those from the lowest poverty quintile (adjusted odds ratio 1.60; 95% confidence interval 1.52-1.69); a similar pattern was noted for vehicle access (adjusted odds ratio 1.77; 95% confidence interval 1.68-1.87). At the ecological level, there were significant, graded relationships between PMN rates and poverty and vehicle access (both P < .0001); these gradients extended across all medication classes.

Conclusions: Poverty and vehicle access are related to significant differences in prescription- and ecological-level PMN across 1 metropolitan area. Pharmacists and pharmacies can be key partners in population health efforts.

FIGURE 1

Zip codes with prescriptions filled between October 1, 2016, and April 1, 2017, and corresponding rates of 30-day PMN.

FIGURE 2

A, Linear regression models used to assess associations between zip code PMN as measured at 30 days and the continuous measure of zip code percentage of individuals living below the federal poverty level. B, Linear regression models used to assess associations between zip code PMN as measured at 30 days and the percentage of households without access to a vehicle.

FIGURE 3

A, PMN as measured at 30 days for medication classes across the entire sample and for zip code quintiles with the lowest and highest rates of poverty. B, PMN as measured at 30 days for medication classes across the entire sample and for zip code quintiles with the lowest and highest rates of household access to a vehicle.