Circumstances and factors of sleep-related sudden infancy deaths in Japan

Motoki Osawa, Yasuhiro Ueno, Noriaki Ikeda, Kazuya Ikematsu, Takuma Yamamoto, Wataru Irie, Shuji Kozawa, Hirokazu Kotani, Hideki Hamayasu, Takehiko Murase, Keita Shingu, Marie Sugimoto, Ryoko Nagao, Yu Kakimoto

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6 Citations (Scopus)


Background Sudden unexpected death in infancy (SUDI) comprises both natural and unnatural causes of death. However, few epidemiological surveys have investigated SUDI in Japan. Objective This retrospective study was conducted to investigate the latest trends of circumstances and risk factors of SUDI cases in which collapse occurred during sleep. Methods Forensic pathology sections from eight universities participated in the selection of subjects from 2013 to 2018. Data obtained from the checklist form were analyzed based on information at postmortem. Results There were 259 SUDI cases consisting of 145 male infants and 114 female infants with a mean birth weight of 2888 ± 553 and 2750 ± 370 g, respectively. Deaths most frequently occurred among infants at 1 month of age (18%). According to population data as the control, the odds ratio (95% confidence interval) of mother’s age ≤19 years was 11.1 (6.9–17.7) compared with ages 30–39. The odds ratio for the fourth- and later born infants was 5.2 (3.4–7.9) compared with the frequency of first-born infants. The most frequent time of day for discovery was between 7 and 8 o’clock, and the time difference from the last seen alive was a mean of 4.1 h. Co-sleeping was recorded for 61%, and the prone position was found for 40% of cases at discovery. Mother’s smoking habit exhibited an odds ratio of 4.5 (2.9–5.8). Conclusion This study confirmed the trends that have been observed for sudden infant death syndrome; particularly, very high odds ratios were evident for teenage mothers and later birth order in comparison with those in other developed countries. Neglect was suspected in some cases of the prolonged time to discovery of unreactive infants. To our knowledge, this is the first report of an extensive survey of SUDI during sleep in Japan.

Original languageEnglish
Article numbere0233253
JournalPloS one
Issue number8 August 2020
Publication statusPublished - 08-2020
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General


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