Which types of medical expenditure does self-rated health predict?

Objectives: Previous research found that self-rated health (SRH) has good predictive power for medical expenditure and hence is useful as means of risk-adjustment to improve comparability of different groups. This research aims to determine whether this predictive power vary by type of medical expenditure, and whether different domains of SRH contributes differently to this predictive power. Participants: 13,814 adults (18~65 years old) from the Taiwan 2005 National Health Interview Survey (NHIS). NHIS is nationally representative. Methods: The data from the 2005 NHIS was linked to the 2005 and 2006 administrative data from the National Health Insurance (NHI) database. NHI is compulsory for all citizens in Taiwan and covers most of medical services. SRH is measured using SF-36, which consisted of 8 domains of SRH, including four physical health and four mental health evaluations. Types of medical expenditure are classified using the Clinical Classification System (CCS). Results: Within the 8 domains of SF-36, physical functioning and role limitation due to poor physical health conditions were most significantly associated with total high medical expenditures. When sub-classify the medical expenditures using CCS, these two domains contribute the most to chronic disease-related expenditures. On the other hand, the mental domain from the SF-36 has low predictive power of mental-related medical expenditures. Conclusions and policy implications: While SRH is a good risk adjustment tool, domain specific scores may be more meaningful than the overall rating. This is especially true when analyzing specific disease categories. Future research that uses SRH as a risk adjustment should take this into consideration.