Lower respiratory tract infections and gastrointestinal infections among mature babies in Japan

Background: Epidemiologic evidence regarding the background factors of childhood infections in Japan is scarce. The aim of the present study was therefore to investigate the rates and associated factors of hospitalization for lower respiratory tract infections (LRTI) and gastrointestinal infections (GII) among children with birthweight ≥2500 g and ≥37 weeks of gestational age. Method: The data for the study were collected at 18‐month health checkups in one city in Japan. The community database included information on the main outcome (past hospitalization) and 16 host, environmental, and parenting factors. The Kaplan–Meier method and log–rank test were used to determine sex differences in hospital admission for infection, and the Cox regression model to analyze sex‐specific factors associated with the hospitalization. Results: The proportion of children who were admitted to hospital before their 18‐month checkup was 7.1% for LRTI and 2.2% for GII. Hospital admission for LRTI among boys was higher than girls. Multivariate analysis indicated the following LRTI‐associated factors: child‐care attendance (hazard ratio HR]= 1.97) and three or more adults living together (HR = 2.63) for boys; and child‐care attendance (HR = 4.30) and two or more children living together (HR = 4.57) for girls. GII‐associated factors were maternal age <25 years (HR = 3.45) for boys, and hand washing by caregivers after lavatory use and diaper changing (HR = 6.93) for girls. Conclusions: One out of 11 children was hospitalized because of LRTI or GII during their first 18 months, which was associated with a biologic factor (sex), environmental factors (child‐care attendance and family size), and parenting practices (shorter duration of exclusive breast‐feeding and caregivers' unfavorable hygiene practices).