Objectives: Daily toothbrushing behaviour is very effective for the prevention of early childhood dental caries (ECC), but is mostly dependent upon parental management. Intrapersonal association between lower toothbrushing frequency and depression is well known; however, the impact of maternal postpartum depression on child toothbrushing behaviour within the mother-child dyad remains unknown. The aim of this study was to determine the association between the prevalence of maternal postpartum depression and lower toothbrushing frequency in children aged two years.
Methods:A secondary analysis of a data set from the Japan Environment and Children's Study was performed. A total of 104 062 fetuses were enrolled after obtaining informed written parental consent, in which 84 533 mother-infant pairs were included after applying exclusion criteria. The Edinburgh Postpartum Depression Scale (EPDS) was used to evaluate maternal postpartum depression (a total score of ≥9 in EPDS) at one and six months postpartum. Indeed, the participants were classified based on the persistence of postpartum depression: 'Resilient' (no prevalence); 'Improving' (prevalence only at one month postpartum); 'Emergent' (prevalence only at six months postpartum); and 'Chronic' (prevalence at both time points). The association between postpartum depression and a toothbrushing frequency in children (the reference group: more than once per day, the low group: once per day, and the very-low group: less than once per day) was examined using Poisson regression models with adjustments for maternal and child characteristics after multiple imputations for missing data.
Results:The prevalence of maternal postpartum depression at one and six months postpartum was 13.9% and 11.4%, respectively; the proportions of each persistence group were 81.1% ('Resilient'), 7.5% ('Improving'), 5.0% ('Emergent') and 6.4% ('Chronic'). Concerning children's toothbrushing frequency, 51.6% and 0.5% of participants self-reported frequencies of once per day and less than once per day, respectively. The association of maternal postpartum depression with a lower toothbrushing frequency in children consistently had higher relative risks (RRs). However, | 301 TSUCHIYA eT Al. the Environment's Institutional Review Board on Epidemiological Studies (No. 100 406 001), and by the Ethics Committees of all participating institutions (ie