To evaluate quality of life, the tool used here is the Korean language version of World Health Organization Quality of Life Scale- Brief (WHOQOL-BREF) standardized by [34] from the original by WHOQOL Group [35]. The tool of this study uses a 5-point Likert scale and has 26 questions, with scores ranging from 26 to 130 points. Higher scores mean higher quality of life. The Cronbach's alpha for the previous study was .86 [34], and that of the current study was .94.