AUTHOR CONTRIBUTIONS
All the authors have contributed to the preparation of this manuscript. A Koh conceptualized the study; E Yeoh, A Koh and S Fun contributed to data collection, study design and methodology; M Chua and A Koh performed data analysis; M Chua wrote the original draft of the manuscript; E Yeoh, A Koh and M Chua reviewed and edited the manuscript. In addition, all the authors are in agreement with the content of this manuscript.