Socioeconomic inequalities in healthcare services are major public health and healthcare concerns. We have examined the association of income with symptoms, morbidities and healthcare usage in a national sample of the Japanese population.

For this study, data compiled on 21,929 men and 24,620 women from the Comprehensive Survey of the Living Conditions of People on Health and Welfare in 2007 were assessed. Among the survey respondents with symptoms, we compared the prevalences of symptoms and treatments and the number of respondents who received treatments for 16 groups of symptoms and disorders according to household income, from the highest to the lowest, using the relative index of inequalities (RII). The RIIs were computed by age groups [25–59 years (young group) and 60+ years (senior group)].

People with lower incomes had higher prevalences of symptoms and treatments for most of the disorders examined. The RIIs of symptoms and treatments were 1.19 [95% confidence interval (CI) 1.09–1.31] and 1.04 (95% CI 0.93–1.16) for the young group and 1.69 (1.53–1.87) and 1.51 (1.36–1.67) for the senior group, respectively. In terms of treatment prevalence among those with symptoms, the RII was not significantly lower than 1.0 except for a few disorders in the young group.

Our results indicate that income inequalities can be related to the prevalences of various symptoms and morbidities in our Japanese sample population and that these inequalities were greater in the senior group than in the young group. Our results also suggest that lower income is not a substantial barrier to the use of healthcare services by older Japanese individuals, while it is related to lower healthcare usage by individuals of working age.