Does breastfeeding influence sleep? A longitudinal study across the first two postpartum years

Background: The association between breastfeeding and sleep of the gestational parent is poorly understood. This longitudinal study investigated how breastfeeding is associated with total nighttime sleep duration and sleep efficiency (percentage of total sleep time in bed) in nulliparous participants over the first two postpartum years. Methods: Nulliparous participants (N = 155, M_age = 33.45, SD_age = 3.50) self-reported patterns of breastfeeding via telephone interviews and sleep via self-report at 1.5, 3, 6, 12 and 24 months postpartum. Data were analyzed using mixed-effects models, with breastfeeding variables as predictors and sleep variables as outcomes, controlling for relevant covariates. Results: Neither the presence of breastfeeding nor the percentage of human milk in infants' total diets was significantly associated with participants' sleep duration or sleep quality (P-values > 0.08). This finding held after controlling for the number of nighttime feeds (P-values > 0.11). However, greater numbers of nighttime feeds, regardless of feeding content, were strongly associated with shorter sleep duration and poor sleep efficiency (P-values < 0.05). On average, with each additional nighttime feed, nocturnal sleep duration decreased by 6.6-8.4 minutes, and sleep efficiency decreased by 2.88%-3.02%. Conclusions: Data from this study showed that breastfeeding per se was not associated with shorter or poor nocturnal sleep, but the number of nighttime feeds was. Sharing nighttime infant care amongst different carers in the household could help reduce postpartum sleep disturbance and ameliorate its negative impact on wellbeing.