US Drug Prescription Rates Influenced by Race, State Healthcare Laws, and Wealth

The best predictors of which US counties’ patients are most likely to be prescribed higher-priced drugs are income, healthcare costs, and access to exercise opportunities, according to a new study published online in Nature Communications.

Other factors such as state-level laws, insurance networks, or cultural preferences likely explain the remaining variance in brand preference across US counties, according to researchers Rachel D. Melamed, PhD, and Andrey Rzhetsky, PhD, of the University of Chicago. They concluded that a “patchwork” of contrasting medication cultures is in place across the nation, showing “geographically separated sub-Americas” that demonstrate the influences of racial composition, state-level healthcare laws, and wealth.

Their findings are based on an analysis of Truven MarketScan medical claims data covering more than 150 million individuals (nearly half the country’s population), followed for up to 10 years (2003-2013). The authors focused on comparing prescription rates of the 598 most highly prescribed drugs in more than 2300 US counties. The data contain a total of approximately 36 million patient-years.

Among the study’s findings are the following:

• The use of prescribed drugs is significantly more similar for pairs of counties located closer together and for pairs of counties with similar demographics.
• Healthcare providers in urban areas, especially in the Northeast between New York and Washington, DC, tend to prescribe more expensive brand-name drugs, even when the drugs have not been proven to be more efficacious than cheaper alternatives. Some Midwestern and Western states and Northern New England preferred cheaper drugs.
• The fraction of the population that is insured is higher in the Northeast than in the South or West. Some preventive care therapeutic drug classes are prescribed more in the Northeast, and these are generally prescribed more in counties with higher insurance rates (including, fertility drugs, fluoride treatments, and smoking cessation drugs).
• Patterns of prescribing in northern New England (Massachusetts, New Hampshire, Vermont, and Maine) are most like Minnesota and Wisconsin—an unexpected finding, according to the researchers.
• Prescription drug use differs between northern and southern states and between rural and urban states. Across drug classes ranging from antihypertensive to dermatological, urban counties prescribe more brand-only drugs.
• As the degree of “urban-ness” grows, counties have fewer prescriptions for potassium repletion supplements, corresponding with lower use of potassium-depleting diuretics prescribed for hypertension.
• All 7 drugs belonging to the therapeutic class of antipsychotics are prescribed more in North and West counties.
• Allergy and cold medicines are highly used in most Southeast counties. Southeast counties also have greater use of drugs for obesity-related illnesses, including hyperlipidemia, hypertension, and diabetes.

The study was funded by the DARPA Big Mechanism program and by National Institutes of Health grants.

Reference

Melamed RD, Rzhetsky A. Patchwork of contrasting medication cultures across the USA. Nature Communications.2018;9:4022. doi: 10.1038/s41467-018-06205-1.