Wealth-related versus income-related inequalities in dental care use under universal public coverage: a panel data analysis of the Japanese Study of Aging and Retirement.

BACKGROUND There is a substantial body of evidence of income-related inequalities in dental care use, attributed to the fact that dental care is often not covered by public health insurance. Wealth-related inequalities have also been shown to be greater than income-related inequalities. Japan is one of the exceptions, as the the universal pubic health insurance system has covered dental care. The aim of this study was therefore to compare wealth- and income-related inequalities in dental care use among middle-aged and older adults in Japan to infer the mechanisms of wealth-related inequalities in dental care use. METHODS Data were derived from the Japanese Study of Aging and Retirement, a survey of community-dwelling middle-aged and older adults living in five municipalities in eastern Japan. Of the participants in the second wave conducted in 2009, we analyzed 2581 residents. Dental care use was measured according to whether the participant had been seen by a dentist or a dental hygienist in the past year. The main explanatory variables were income and wealth (financial assets, real assets and total wealth). The need for dental care was measured using age, the use of dentures and chewing ability. The concentration indices for the distribution of actual and need-standardized dental care use were calculated. RESULTS Among the respondents, 47.9% had received dental care in the past year. The concentration index of actual dental care use (CI) showed a pro-rich inequality for both income and wealth. The CIs for all three wealth measures were larger than that for income. A broadly comparable pattern was seen after need-standardization (income: 0.020, financial assets: 0.035, real assets: 0.047, total wealth: 0.050). CONCLUSIONS The results showed that wealth-related inequalities in dental care use were greater than income-related inequalities in Japan, where most dental care is covered by the public health insurance system. This suggests that wealth-related inequalities in dental care use cannot be explained by economic budget constraints alone. Further studies should investigate the mechanisms of wealth-related inequalities in dental care use.