Funding for this research was provided by:
Science-Technology Foundation of Guangdong Province (2016A020223005)
National Institutes of Health
the Women and Children’s Foundation of Guangdong Province (5100071020195)
the All-China Women’s Federation
Received: 20 June 2019
Accepted: 11 December 2019
First Online: 23 December 2019
Ethics approval and consent to participate
: According to the article 16 of the General Principles of the Civil Law of the People’s Republic of China and the article 14 of International Ethical Guidelines for Biomedical Research Involving Human Subjects, for participants aged 10–16 years, written informed consents were obtained from both children themselves and one of their current guardians, and for participants aged 3–9 years, written informed consents were obtained from one of their current guardians before the survey. Usually, parents are statutory guardians of minors. However, when both parents were apart from children, the written informed consent form was obtained from one of the current guardians designated by a parent.This study was approved by the Biomedical Research Ethics Review Committee of the School of Public Health, Sun Yat-sen University (Guangzhou, China).
: Not applicable.
: The authors declare that they have no competing interests.