From the Department of Epidemiology for Community Health and Medicine, Kyoto Prefectural University of Medicine, Kyoto, Japan (Yoshida, Koyama).

Department of Environmental Epidemiology, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan, Kitakyushu, Japan (Ishimaru).

Department of Hygiene, Public Health and Preventive Medicine, Showa University School of Medicine, Tokyo, Japan (Minoura).

Department of Molecular-Targeting Prevention, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan (Mutoh).

Cancer Control Center, OsakaInternational Cancer Institute, Osaka, Japan (Tabuchi).

Funding: None.

Conflicts of interest: None Declared.

Ethical considerations and disclosures: All procedures were conducted in accordance with the ethical standards of the Helsinki Declaration of 1975, as revised in 2013. The study protocol was reviewed and approved by the Research Ethics Committee of the Osaka International Cancer Institute (approved on June 19, 2020; approval number 20084). The Internet survey agency respected the Act on the Protection of Personal Information in Japan. All participants provided Internet-based informed consent before responding to the online questionnaire. This study was exempted from the obligation to obtain informed consent from the parents/guardians of minors younger than 18 years in Japan. The Ethical Guidelines for Medical and Health Research Involving Human Subjects enforced by Japan's Ministry of Education, Culture, Sports, Science and Technology and Japan's Ministry of Health, Labour and Welfare addressed, “when the research individuals have completed junior high school or another relevant schooling, or are 16 years or older, and are considered to have enough judgment concerning the research to be implemented on themselves, and the following matters are prescribed in the research protocol, and the chief executive of the research implementing entity approves the research to be carried out after relevant ethical review committee deliberation, informed consent shall be obtained not from representative but from the said research subject. (1) The research to be implemented does not involve any invasiveness; and (2) information concerning the implementation of the research, including the purpose of the research and how specimens or information will be handled, is made public, and opportunities to refuse that the research is commenced or continued on the research subject are ensured for persons who exercise parental authority over the said research subject and guardians of the minor.” All participants completed junior high school; the present study did not involve any invasive procedures, and the approval of the research ethics committee of the Osaka International Cancer Institute for the study protocol was obtained as aforementioned. A credit point known as “Epoints,” which could be used for Internet shopping and cash conversion, was provided to the participants as an incentive.

Address correspondence to: Tamami Yoshida, Department of Epidemiology for Community Health and Medicine, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kamigyo-ku, Kyoto 602-8566, Japan ([email protected]).