No Cost Sharing for Public Assistance Recipients and Health Service Usage in Japan.

IMPORTANCE

In Japan, the public assistance (PA) system for low-income individuals provides medical aid that covers all health care costs (no cost sharing). However, little is known about how health care service utilization changes after PA certification.

OBJECTIVE

To examine the trajectories of outpatient medical and dental care utilization among PA recipients before and after PA certification.

DESIGN, SETTING, AND

PARTICIPANTS

Longitudinal data from a municipality in Japan participating in the Longevity Improvement Fair Evidence Study from 2017 to 2022 were used. Generalized estimating equations were used to calculate absolute differences and relative ratios in health care service utilization before and after PA certification. An interrupted time-series analysis (ITSA) was performed to examine the trends in health care service use based on monthly panel data. The elasticity of each health care service was also calculated. The participants were individuals who switched from National Health Insurance to PA and were 20 years and older. The analysis was performed in 2024.

EXPOSURE: PA certification.

MAIN OUTCOMES AND MEASURES: Outpatient medical and dental care expenditures, visits, and unit costs per month from 1 year before to 1 year after PA certification.

RESULTS

Overall, 2893 study participants were analyzed (mean [SD] age, 54.2 [15.3] years; 1501 women [51.9%]). For outpatient medical care, the mean (SD) expenditures per month before and after PA certification were ¥16 565 (¥53 159) and ¥22 442 (¥53 443), respectively (converting to US dollars using the rate of ¥100 = $0.68 based on 2025 rates). For outpatient dental care, the mean (SD) expenditures per month before and after PA certification were ¥1727 (¥3726) and ¥3978 (¥6894), respectively. The ITSA showed significant increases in outpatient expenditure immediately after PA certification: ¥2681 (95% CI, 317-5046) and ¥2330 (95% CI, 1896-2764) in medical and dental care, respectively.

CONCLUSIONS AND RELEVANCE: This study found that eliminating cost sharing under a PA system was associated with increased outpatient health service use, particularly for dental care. These findings highlight financial barriers to care among low-income populations and suggest that no cost-sharing policies can improve access but may require policy measures to address overuse.