Effect of no cost sharing for paediatric care on healthcare usage by household income levels: regression discontinuity design

Abstract

Objectives To investigate the impact of no cost sharing on paediatric care on usage and health outcomes, and whether the effect varies by household income levels.Design Regression discontinuity design.Setting Nationwide medical claims database in Japan.Participants Children aged younger than 20 years from April 2018 to March 2022.Exposure Co-insurance rate that increases sharply from 0% to 30% at a certain age threshold (the threshold age varies between 6 and 20 years depending on region).Primary outcome measures The outpatient care usage (outpatient visit days and healthcare spending for outpatient care) and inpatient care (experience of any hospitalisation and healthcare spending for inpatient care).Results Of 244 549 children, 49 556 participants were in the bandwidth and thus included in our analyses. Results from the regression discontinuity analysis indicate that no cost sharing was associated with a significant increase in the number of outpatient visit days (+5.26 days; 95% CI, +4.89 to +5.82; p<0.01; estimated arc price elasticity, −0.45) and in outpatient healthcare spending (+US$369; 95% CI, +US$344 to +US$406; p<0.01; arc price elasticity, −0.55). We found no evidence that no cost sharing was associated with changes in inpatient care usage. Notably, the effect of no cost-sharing policy on outpatient healthcare usage was larger among children from high-income households (visit days +5.96 days; 95% CI, +4.88 to +7.64, spending +US$511; 95% CI, +US$440 to +US$627) compared with children from low-income households (visit days +2.64 days; 95% CI, +1.54 to +4.23, spending +US$154; 95% CI, +US$80 to +US$249).Conclusions No cost sharing for paediatric care was associated with a greater usage of outpatient care services, but did not affect inpatient care usage. The study found that this effect was more pronounced among children from high-income households, indicating that the no cost sharing disproportionately benefits high-income households and may contribute to larger disparities.