Assessment of Racial/Ethnic and Income Disparities in the Prescription of Opioids and Other Controlled Medications in California

Abstract

Importance: Most drug epidemics in the United States have disproportionately affected nonwhite communities. Notably, the current opioid epidemic is heavily concentrated among low-income white communities, and the roots of this racial/ethnic phenomenon have not been adequately explained.

Objective: To examine the degree to which differential exposure to opioids via the health care system by race/ethnicity and income could be driving the observed social gradient of the current opioid epidemic, as well as to compare the trends in the prevalence of prescription opioids with those observed for stimulants and benzodiazepines.

Design, setting, and participants: This population-based study used 2011 through 2015 records from California's prescription drug monitoring program (Controlled Substance Utilization Review and Evaluation System), which longitudinally tracks all patients receiving controlled substance prescriptions in the state and contained unique records for 29.7 million individuals who received such a prescription from 2011 to 2015. Data were analyzed between January and May 2018.

Exposures: A total of 1760 zip code tabulation areas (ZCTAs) in California, with associated racial/ethnic composition and per capita income.

Main outcomes and measures: The percentage of individuals receiving at least 1 prescription each year was calculated for opioids, benzodiazepines, and stimulants.

Results: A nearly 300% difference in opioid prescription prevalence across the race/ethnicity-income gradient was observed in California, with 44.2% of adults in the quintile of ZCTAs with the lowest-income/highest proportion-white population receiving at least 1 opioid prescription each year compared with 16.1% in the quintile with the highest-income/lowest proportion-white population and 23.6% of all individuals 15 years or older. Stimulant prescriptions were highly concentrated in mostly white high-income areas, with a prevalence of 3.8% among individuals in the quintile with the highest-income/highest proportion-white population and a prevalence of 0.6% in the quintile with the lowest-income/lowest proportion-white population. Benzodiazepine prescriptions did not have an income gradient but were concentrated in mostly white areas, with 15.7% of adults in the quintile of ZCTAs with the highest proportion-white population receiving at least 1 prescription each year compared with 7.0% among the quintile with the lowest proportion-white population.

Conclusions and relevance: The race/ethnicity and income pattern of opioid overdoses mirrored prescription rates, suggesting that differential exposure to opioids via the health care system may have induced the large, observed racial/ethnic gradient in the opioid epidemic. Across drug categories, controlled medications were much more likely to be prescribed to individuals living in majority-white areas. These discrepancies may have shielded nonwhite communities from the brunt of the prescription opioid epidemic but also represent disparities in treatment and access to all medications.

Figure 1.. Opioid Overdose Deaths and Prescription Prevalence

A, Annual age-standardized opioid overdose death rates per 100 000 people. B, Annual prevalence of receiving at least 1 prescription for an opioid among individuals 15 years or older. Both figures represent the entire state of California, showing quartiles of mean annual rates during the 2011 through 2015 study period. The y-axis represents the percentage of individuals in each zip code tabulation area identifying as non-Hispanic white, by quintiles (Qs). The x-axis represents quintiles of the mean per capita annual income at the zip code tabulation area level. Values for all 25 quintile-quintile pairs are shown with color and text.

Figure 2.. Benzodiazepine and Stimulant Prescription Prevalences

Annual prevalence of receiving at least 1 prescription for a benzodiazepine (A) or a stimulant (B). Both figures represent the entire state of California, showing quartiles (Qs) of mean annual rates during the 2011 through 2015 study period. A, Values for all individuals 15 years or older. B, Data for all individuals of any age because stimulant prescription receipt is highest in the age group of 10 to 14 years.

Figure 3.. Prescription Prevalence, Race/Ethnicity Distribution, and Income Level for the Los Angeles Case Study

Data are mapped at the zip code tabulation area level. Prescription prevalence of opioids (A) and benzodiazepines (B) are shown for individuals 15 years or older and stimulants (C) for individuals of all ages. Mean per capita income (×$1000) (D) and the percentage of individuals identifying as non-Hispanic white (E) are also shown. All values are shown in quintiles and represent means of annual rates from 2011 through 2015.