OBJECTIVES:

Economic burden of disease is often assessed using productivity impairment and indirect costs (IC). IC can be estimated using the human capital method using wages or gross domestic product (GDP). Research comparing methods using wages and GDP are limited. This research evaluates differences and implications when calculating IC using median wages vs GDP.

METHODS:

Data were obtained from the 2023 US National Health and Wellness Survey (NHWS), a population-based, cross-sectional, online, patient-reported survey of adults (≥18 years of age). Respondents diagnosed with asthma or psoriasis or were caregivers of adults or children with disease were included. Impairment was assessed using the Work Productivity and Activity Impairment (WPAI) scale. IC using wages were calculated using data from the 2023 US Bureau of Labor Statistics stratified by age, sex, and race. IC using GDP were calculated with unstratified 2023 GDP/capita estimates from the St. Louis Federal Reserve. Descriptive statistics and Wilcoxon rank-signed tests for paired data were used to evaluate differences between the two calculations of IC.

RESULTS:

Of the 12,772 total respondents, 57.6% were female and mean age was 44.9 (SD=16.1) years. Median (Q1,Q3) IC of asthma patients (n=3,412) using wages were $8,525($0,$21,750) while median IC using GDP were $11,610($0,$29,522) (p<0.001). Psoriasis patients (n=1,074) had IC from median wages of $7,634($0,$21,720) compared to $9,205($0,$26,785) IC from GDP (p<0.001). IC among caregivers of adults (n=6,857) (IC wages $8,304($2,282,$21,548) vs IC GDP $10,780($3,151,$28,195) and IC among caregivers of children (n=7,099) (IC wages $8,304($2,044,$21,720) vs IC GDP $10,615($2,819,$29,024)) were both significantly higher (all p<0.001) when GDP was used. Overall, IC were at least 20% higher when using GDP compared to wages.

CONCLUSIONS:

Using wages provides a more conservative and comprehensive approach in IC calculations, compensating for the lack of demographic earnings variation in GDP estimates.