Horizontal inequity in healthcare access under the universal coverage in Japan; 1986-2007

Universal coverage of healthcare aims at securing access to appropriate healthcare for all at an affordable cost. Since 1961, Japan's national health insurance has provided an equal package of benefits including outpatient, inpatient, dental, and pharmaceutical services. Reduced copayment and other welfare programs are available to the elderly. However, social health insurance may not be a panacea to achieve healthcare for all, especially when facing household impoverishment due to economic stagnation. Using time-series cross-sectional data of a nationally representative survey of Japan, we assessed the degree of inequity in healthcare access in terms of the "equal treatment for equal needs" concept, to identify the impact of changing economic conditions on people's healthcare access. Concentration indices of actual healthcare use (C(M)) and standardized health status as a marker of healthcare needs (C(N)) were obtained. We decomposed C(M) to identify factors contributing to inequalities in healthcare use. Results showed that horizontal inequities in healthcare access in favor of the rich gradually increased over the period with a widening health gap among the poor. The inequality in favor of the rich was specifically observed among people aged 20-64 years, whereas high horizontal equity was achieved among those aged >65 years. Decomposition of C(M) also demonstrated that income and health status were major contributors to widening inequality, which implies that changes in household economic conditions and copayment policy during the study period were responsible for the diminished horizontal equity. Our results suggest that the achievement of horizontal equity through universal coverage should be regarded as an ongoing project that requires continuous redesign of contribution and benefit in the nation's healthcare system.