Income-based inequality in nationwide general health checkup participation in Japan

In Japan, it is mandatory for employers to provide general health checkup opportunities to employees. Although many companies have subsidized checkups for employees' dependent family members, their participation is low. We assessed income-based inequality in the participation of employees' dependents in the general health checkup.

This is a cross-sectional descriptive study. Annual participation rate in general health checkup and various factors including income, age, and sex were collected and analyzed to examine the income-based inequality of participation rate in general health checkup.

The data for the present study were sourced from the Fukuoka Branch of the Japan Health Insurance Association, a large medical insurer in Japan. We extracted data of 196,057 dependents aged 40-74 years. We conducted a multiple logistic regression analysis using participation from April 2015 to March 2016 as dependent variable and income category ranging from 1 (lowest) to 4 (highest) between April and June 2015 as independent variable (adjusted for sex and age). We computed slope index of inequality (SII) and relative index of inequality (RII) based on income category.

Higher the income, the more likely were dependents to participate in the general health checkup. SII for the participation rate of general health checkup ranged between -0.02 (95% confidence interval [CI]: -0.07 to 0.03) and 0.06 (0.03-0.09) for men; 0.03 (0.01-0.06) and 0.10 (0.09-0.11) for women. RII for the participation rate of general health checkup ranged between -0.19 (95% CI: -0.66 to 0.29) and 0.88 (0.15-1.61) for men; 0.22 (0.05-0.39) and 0.68 (0.60-0.76) for women. The highest inequality existed for men in their 50s and 60s and women in their 50s; the lowest inequality was among men and women aged 70-74 years.

There was income-based inequality in participation in the general health checkup among dependents (family members) of the insured persons. The degree of inequality differed with age group. It cannot be explained solely by financial barrier among low-income group, rather it may reflect Japanese unique context in medical insurance system.