Comprehensive cost of illness of all diseases in Japan: Measurement of the social burden of diseases in a super-aged society

•Traditional indicators for social burden of disease is too complex for policy-makers.•The comprehensive cost of illness (CCOI) method is easy to use for policy-making.•CCOI in 2017 was 90.6 trillion yen (16.6% of GDP) in Japan.•From 2002 to 2017, CCOI increased 1.36 times.•The three top-ranked diseases influencing CCOI did not change during this period. Evaluation of the social burden of illness is important for policy decision-making. However, policy-makers find indicators traditionally used in the healthcare field difficult to use because calculation of these indicators is complex and the unit of indicators is often expressed on “years” basis. The aim of this study was to measure the burden of all diseases using the Comprehensive Cost of Illness (CCOI) method and to provide indicators that are easy to use for policy-making. Utilizing government-based nationwide statistical data, we used the CCOI method to estimate the social burden of illness from 2002 to 2017. CCOI consists of direct costs (medical direct cost and formal care cost) and indirect costs (morbidity cost, mortality cost, and informal care cost). From 2002 to 2017, CCOI increased from 66.5 trillion yen (12.9% of the gross domestic product [GDP]) to 90.6 trillion yen (16.6% of GDP). From 2002 to 2017, the three top-ranked diseases influencing CCOI did not change. The ranking of these diseases (from first to third) is as follows: circulatory system diseases, neoplasms, and digestive diseases. The trend of CCOI is consistent with the trends of national health expenditure and disability-adjusted life years. The CCOI method is expressed in monetary terms, so the effects of aging and the development of medical technology are represented by trends in each cost and are considered valuable as the basis of health policy, instead of national health expenditure. Measuring the social burden of disease is important for making policy decisions. There have been indicators to measure the burden of disease in the past, but they have been complex and difficult to use because they are measured in "years". We have developed a comprehensive cost-of-illness method (CCOI) that includes the burden of long-term care by applying a method called the cost-of-illness method (COI), which expresses the burden of illness in monetary terms. Using this method, we measured the cost of illness in Japan's aging population, which in 2017 was 66.5 trillion yen (approximately US$532 billion), accounting for 12.9% of GDP. Since this