Quality Of Life In Rheumatoid Arthritis: Cross-National Comparison Study Between US and South Korea

Abstract

Background/Purpose: Quality of life (QOL) is a well-established outcome for rheumatoid arthritis (RA) trials. To perform trials with QOL as an outcome involving many countries, it is valuable to compare QOL measures across countries. The objective of this study was to compare health-related quality of life (HRQOL) of rheumatoid arthritis (RA) patients between United States (US) and South Korea.

Methods: Two year follow-up data on health and HRQOL measured with EuroQoL-5 dimension (EQ-5D) between 2009 and 2011 were compared between US-based (BRASS) and Korean-based (KORONA) cohorts. A total of 1,166 subjects (187 from BRASS and 979 from KORONA) were included in this study to compare the cross-sectional differences in QOL in 2009 and the longitudinal two-year change through 2011. We performed multivariate linear regression analyses to identify factors associated with QOL and its changes in each cohort.

Results: The mean (standard deviation) of EQ-5D score (1.0 being the best possible score) of BRASS subjects was 0.82 (0.16) and that of KORONA subjects was 0.69 (0.25) (P <0.01) at baseline in 2009 (see table). Disease activity score (DAS) 28 (P<0.01) and modified health assessment questionnaire (MHAQ) score (P<0.01) were inversely associated high QOL in both cohorts. Income level (P<0.01) was positively and the number of comorbidities (P<0.01) was negatively associated with QOL only in KORONA (see table). Mean changes in QOL were not different between cohorts (P=0.17). Only changes in DAS28 and MHAQ during 2 years were significantly associated with the change in QOL in both cohorts.

Conclusion: In this cross-national comparison study, changes in QOL and predictors for QOL were comparable between US-based BRASS and Korean-based KORONA, in spite of the differences in baseline characteristics and QOL level in each population.