AUTHOR=Ruan Huijuan , Zhang Yajie , Tang Qingya , Zhao Xuan , Zhao Xuelin , Xiang Yi , Geng Wei , Feng Yi , Cai Wei 

TITLE=Sleep duration of lactating mothers and its relationship with feeding pattern, milk macronutrients and related serum factors: A combined longitudinal cohort and cross-sectional study

JOURNAL=Frontiers in Nutrition

VOLUME=Volume 9 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2022.973291

DOI=10.3389/fnut.2022.973291

ISSN=2296-861X

ABSTRACT=Objective: Insufficient sleep is common in postpartum mothers. The main objectives of this study are to explore the sleep duration among Chinese lactating mothers and preliminarily investigate the relationship between sleep duration and feeding pattern. The secondary objectives are to investigate the relationships between sleep duration and milk macronutrients and between maternal-related indicators. 
Methods: The present study comprises a longitudinal and a cross-sectional cohort from December 2019 to December 2020. Postpartum lactating women living in Shanghai were recruited through online and offline recruitment. The subjects were included in the longitudinal cohort or cross-sectional study based on their lactation period at the time of recruitment. The longitudinal cohort included a total of 155 mothers. Human milk and feeding pattern were measured and collected at 2-4 months and 5-7 months postpartum. At four predetermined follow-up time points, data on sleep duration was collected (at the time of recruitment, 2-4 months postpartum, 5-7 months postpartum, and 12-17 months postpartum). The cross-sectional study included 35 lactating mothers (2-12 months postpartum) who reported their sleep duration and provided blood samples. Mid-infrared spectroscopy (MIRS) method was used to analyze the  breast milk macronutrients, while MT, GH, GHRL, GLP-1, PRL, and CCK in maternal blood were determined by ELISA.
Results: The maternal sleep duration before pregnancy was 8.14±1.18 hours/d (n=115), 7.27±1.31 hours/d (n=113) for 2-4 months postpartum, 7.02±1.05 hours/d (n=105) for 5-7 months postpartum, and 7.45±1.05 hours/d (n=115) for 12-17 months postpartum. At 2-4 months postpartum, the frequency of formula feeding per day is related to reduced maternal sleep duration. At 2-4 months and 5-7 months postpartum, the relationship between macronutrients in breast milk and the mother's sleep duration was insignificant. Other than the positive correlation found between maternal GHRL and sleep duration, no significant relationship was observed between sleep duration and other indexes.
Conclusions: Postpartum mothers generally sleep less, but there is no correlation between insufficient sleep and the macronutrient content of breast milk. Formula feeding may be related to the mother's sleep loss, while breastfeeding may be related to increased maternal sleep duration. The findings suggest that sleep duration is related to maternal serum GHRL.