An analysis of length of hospital stay for diabetes patients in Japan by the Box-Cox Transformation model

Thursday 19 May 2016, 1.00PM to 2.00pm

Speaker(s): Nawata Kazumitsu (University of Tokyo)


Diabetes has become a very important disease both in medical and economic terms. Moreover, diabetes can cause serious complications such as vision loss, kidney disease (nephropathy), heart failure, and stroke. If the costs of taking care of the comorbidities and complications of diabetes were included, the medical costs of diabetes would likely be much higher. The Public Health Agency of Canada has reported that the “direct health care costs may be as much as 4.5 times higher than when looking at diabetes alone.” In the United States, the total cost of diagnosed diabetes was estimated at $245 billion in 2012 according to American Diabetes Association (ADA). According to the OECD, the annual cost of diabetes prevention and treatment is approximately 90 billion euro in Europe alone. The International Diabetes Federation (IDF) reported that the number of people with diabetes was 387 million in 2014, or 8.3% of the world population, and was expected to increase by 205 million in 2035. In Japan, the potential population with diabetes age 20 or over was estimated as 16.2% and 9.2% of the male and female population in 2013.

In this paper, we analyzed length of stay (LOS) in hospitals and medical expenditures for type 2 diabetes patients. LOS was analyzed by the power Box-Cox transformation model when variances differed among hospitals. We proposed a new test and consistent estimator. We rejected the homoscedasticity of variances among hospitals, and then analyzed the LOS of 12,666 type 2 diabetes patients hospitalized for regular medical treatments collected from 60 general hospitals in Japan. The variables found to affect LOS were age, number of comorbidities and complications, introduced by another hospital, one-week hospitalization, 2010 revision, specific -hospitalization -period (SHP), and principal diseases E11.5, E11.6 and E11.7. There were surprisingly large differences in ALOS among hospitals even after eliminating the influence of characteristics and conditions of patients.

We then analyzed daily medical expenditure (DME) by the ordinary least squares methods. The variables that affected DME were LOS, number of comorbidities and complications, acute hospitalization, hospital’s own outpatient, season, introduced by another hospital, one-week hospitalization, 2010 revision, SHP, time trend, and principal diseases E11.2, E11.4 and E117. The DME did not decrease after the SHP. After eliminating the influences of characteristics and conditions of patients, the differences among hospitals were relatively small, 12% of the overall average. LOS is the main determinant of medical expenditures, and new incentives to reduce LOS are needed to control Japanese medical expenditures. Since at least 99% of patients require medical care after leaving the hospital, systems that take proper care of patients for long periods of time after hospitalization are absolutely necessary for efficient treatment of diabetes.

Location: Economics Staff Room - A/EC202

Admission: Staff and PhD Students