Cross-sectional associations between early mobile device usage and problematic behaviors among school-aged children in the Hokkaido Study on Environment and Children's Health.

"Declaration Ethics approval and consent to participateThe institutional ethical board for human gene and genome studies at Hokkaido University Center for Environmental and Health Sciences (reference no. 139, August 30, 2022) and Hokkaido University Graduate School of Medicine (May 31, 2003) approved the study protocol. Written informed consent was obtained from all participants at the time of enrollment. Consent for publicationNot applicable. Availability of data and materialThe datasets generated and/or analyzed during the current study are not publicly available because the study involves human participants with a nondisclosure provision of individual data stated in the written informed consent in order to prevent compromise of study participants’ privacy but are available from the corresponding author upon reasonable request. Competing interestsThe authors declare no conflict of interest. FundingThis work was supported by the Grant-in-Aid for Health Science Research from the Japanese Ministry of Internal Affairs and Communications (JPMI10001). Authors’ contributionsReiko Kishi designed the study and developed the methodology. Chihiro Miyashita, Keiko Yamazaki, Naomi Tamura, and Atsuko Ikeda-Araki, collected the data and performed the analyses. Chihiro Miyashita, Keiko Yamazaki, and Naomi Tamura drafted the manuscript. Reiko Kishi, Satoshi Suyama, Takashi Hikage, Manabu Omiya, and Masahiro Mizuta provided critical revision of the manuscript. All authors take full responsibility for the content of this paper. All authors read and approved the final manuscript. AcknowledgementsWe would like to express our appreciation to all of the study participants of the Hokkaido Study on Environment and Children’ Health. We also express our profound gratitude to all personnel in the hospitals and clinics that collaborated with the study, including Sapporo Toho Hospital, Keiai Hospital, Endo Kikyo Maternity Clinic, Shiroishi Hospital, Memuro Municipal Hospital, Aoba Ladies Clinic, Obihiro-Kyokai Hospital, Akiyama Memorial Hospital, Sapporo Medical University Hospital, Hokkaido University Hospital, Kitami Red Cross Hospital, Hoyukai Sapporo Hospital, Gorinbashi Hospital, Hashimoto Clinic, Asahikawa Medical College Hospital, Hakodate Central General Hospital, Ohji General Hospital, Nakashibetsu Municipal Hospital, Sapporo Tokushukai Hospital, Asahikawa Red Cross Hospital, Wakkanai City Hospital, Kushiro Rosai Hospital, Sapporo-Kosei General Hospital, Shibetsu City General Hospital, Nikko Memorial Hospital, Sapporo City General Hospital, Kohnan Hospital, Hakodate City Hospital, Hokkaido Monbetsu Hospital, Tenshi Hospital, Hakodate Goryoukaku Hospital, Nakamura Hospital, Kin-ikyo Sapporo Hospital, Kitami Lady’s Clinic, Engaru-Kosei General Hospital, Kushiro Red Cross Hospital, Nayoro City General Hospital, and Obihiro-Kosei General Hospital. Competing interests The authors declare no conflict of interest."

"Funding This work was supported by the Grant-in-Aid for Health Science Research from the Japanese Ministry of Internal Affairs and Communications (JPMI10001)."