Self-Reported Prevalence and Risk Factors for Shaking and Smothering Among Mothers of 4-Month-Old Infants in Japan

BACKGROUND: To estimate the prevalence of shaking and smothering and to determine risk factors in a population-based sample of mothers with 4-month-old infants in Japan. METHODS: We administered a questionnaire to women who participated in a 4-month health checkup program in Aichi Prefecture, Japan (n = 6487; valid response rate, 66.8%), and assessed frequency of shaking and smothering during the past 1 month, as well as maternal, infant, and familial characteristics. Associations of shaking, smothering, and either shaking or smothering with possible risk factors were analyzed using multiple logistic regression. RESULTS: Self-reported prevalence of shaking, smothering, and either shaking or smothering at least once during the past month was 3.9% (95% confidence interval [CI], 3.5%–4.4%), 2.7% (95% CI, 2.3%–3.1%), and 5.4% (95% CI, 4.9%–6.0%) respectively. Several different risk factors were found for shaking and smothering. Risk factors for either shaking or smothering were age 34 years or younger (especially 24 years or younger), age 40 years or older, full-time working, later attendance at 4-months health checkup, primiparity, living in a detached house, living on the 2nd floor or higher (especially on the 10th floor or higher), economic adversity, perceived excessive crying, and postpartum depression. Protective factors against infant abuse were living in a four-room house and having a larger number of people to consult with. CONCLUSIONS: Self-reported prevalences of shaking and smothering among mothers in Japan were similar to prevalences reported in western countries. These finding may be useful for identifying mothers at increased risk of shaking and smothering their infants.