Insufficient Sleep and Incidence of Dental Caries in Deciduous Teeth among Children in Japan: A Population-Based Cohort Study.

OBJECTIVES: To examine whether late bedtime and short nighttime sleep duration at age 18 months are associated with risk of caries in deciduous teeth. STUDY DESIGN: Population-based cohort study using health check-up data of 71 069 children born in Kobe City, Japan, who were free of caries at age 18 months and had information on sleep variables at age 18 months and records of dental examinations at age 3 years. Sleep variables were assessed by standardized parent-reported questionnaires, and the incidence of caries in deciduous teeth was defined as the occurrence of at least 1 decayed, missing, or filled tooth assessed by qualified dentists without radiographs. Logistic regression was used to estimate the effects of late bedtime and short sleep duration on dental caries with adjustment for clinical and lifestyle characteristics. RESULTS: Overall, 11 343 (16.0%) cases of caries were observed at age 3 years. aORs for children with late or irregular bedtimes compared with those with bedtimes before 21:00 were 1.26 (95% CI 1.19-1.33), 1.48 (1.38-1.58), 1.74 (1.58-1.92), 1.90 (1.58-2.29), and 1.66 (1.53-1.81) for bedtimes at 21:00, 22:00, 23:00, 0:00, and irregular bedtime, respectively. aORs for children with short or irregular sleep duration compared with those with sleep duration of ≥11 hours were 1.30 (95% CI 1.15-1.47), 1.16 (1.09-1.24), 1.11 (1.05-1.18), and 1.35 (1.25-1.46) for sleep duration of ≤ 8, 9, 10 hours, and irregular sleep duration, respectively. CONCLUSIONS: In this exploratory study, late bedtime and short sleep duration were both consistently associated with increased risk of caries in deciduous teeth.

Caesarean delivery and anaemia risk in children in 45 low- and middle-income countries.

Caesarean delivery (CD) may reduce placental transfusion and cause poor iron-related haematological indices in the neonate. We aimed to explore the association between CD and anaemia in children aged <5 years utilising data from Demographic and Health Surveys conducted between 2005 and 2015 in 45 low- and middle-income countries (N = 132,877). We defined anaemia categories based on haemoglobin levels, analysed each country's data separately using propensity-score weighting, pooled the country-specific odds ratios (ORs) using random effects meta-analysis, and performed meta-regression to determine whether the association between CD and anaemia varies by national CD rate, anaemia prevalence, and gross national income. Individual-level CD was not associated with any anaemia (OR 0.95, 95% confidence interval (CI) [0.86, 1.06]; I2  = 40.2%), mild anaemia (OR 0.91, 95% CI [0.81, 1.02]; I2  = 24.8%), and moderate/severe anaemia (OR 0.97, 95% CI [0.85, 1.11]; I2  = 47.7%). CD tended to be positively associated with moderate/severe anaemia in upper middle-income countries and negatively associated with mild anaemia in lower middle-income countries; however, meta-regression did not detect any variation in the association between anaemia and CD by the level of income, CD rate, and anaemia prevalence. In conclusion, there was no evidence for an association between CD and anaemia in children younger than 5 years in low- and middle-income countries. Our conclusions were consistent when we looked at only countries with CD rate >15% with data stratified by individual-level wealth status and type of health facility of birth.