Contributions
WRH conceived of the study and made substantial contributions
to study design, data acquisition, data analysis and
result interpretation and discussions. CWP took responsibility
for data collection and participated in data analysis and
interpretation. HCY helped for statistical analysis and
research design, assisted in interpreting the results and writing
the manuscript. She also took responsibility for drafting,
submitting and revising the manuscript. HCH and
HCT helped for data collection and contributed to discussions.