Characterization of the Walmart Pharmacy Patient Population and Their Exposure to High Heat Indices to Inform Who Is at Risk of Heat-Related Events and Future Pharmacological Safety Interventions

BACKGROUND: As environmental temperatures increase, prescription medication users of certain drug classes, especially those in rural areas and males ≥18 years old, are at increased risk of heat-related illness.

OBJECTIVES: To characterize populations at increased risk of heat-related illness and inform pharmacological safety interventions based on individual-level data on prescriptions received, geography, gender, age group, and heat index.

METHODS: CDC guidance informed which drug classes were associated with heat-related events. Patients receiving prescriptions, as defined by Medispan drug class-level, between May 1-September 30, 2023, for one (C1), two (C2), or three (C3) drug classes were included. Descriptive analyses characterized the study population overall and by age group, gender, region, and cohort. Daily maximum heat indices were calculated from ERA5-Land data using the Magnus Formula. The number of patients exposed to a monthly USA state mean heat index of ≥85°F was estimated. Data management and analyses were conducted with BigQuerry and Python v3.11.4.

RESULTS: Overall, 10,230,771 patients were included, with 4,434,853 (43.3%) in C1, 2,623,932 (25.6%) in C2, and 3,171,986 (31.0%) in C3. Most (51.3%) resided in the South and were >40 y.o (83.1%). The median (IQR) number of prescriptions sold from May 1-September 30, 2023 varied by cohort: C1: 3.0 (IQR 2.0-5.0), C2: 5.0 (IQR 4.0-8.0), C3: 10.0 (IQR 7.0-15.0). Overall, 6,105,874 (59.68%) patients were exposed to a mean heat index ≥85° Fahrenheit. Over one third of the study population (37.1%) resided in the 10 states with the highest mean heat indices.

CONCLUSIONS: Nearly eight million patients receiving prescriptions were exposed to a mean heat index ≥85 Fahrenheit during the study period. Further research should evaluate how pharmacies can educate patients about their increased risk of heat-related events and promote behaviors associated with pharmacological safety.