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Introduction In early childhood, irregular sleep schedules that may promote circadian rhythm misalignment predict greater weight gain. However, circadian rest-activity (CRA) rhythmicity in infancy in relation to growth is understudied. The aim of the present study was to investigate the association between newborn circadian rest-activity rhythmicity and change in weight-for-age from birth to three months. Methods Data were captured as a secondary data analysis from the Snuggle Bug / Acurrucadito Study (see Support). English or Spanish speaking mothers (n=41, age M±SD=33.1±4.6y, 31.7% Hispanic/Latina) and their full-term (≥37wk) infants of normal weight (2.5-4kg; 58.5% female; 25.6% WIC enrolled) were recruited from Phoenix, Arizona. CRA rhythmicity was measured at eight weeks with ankle-worn Micro Motionloggers (Ambulatory Monitoring Inc.) for five 24hr periods at one-minute epochs. CRA metrics assessed included 24hr autocorrelation, mesor, magnitude, acrophase, goodness-of-fit R2, interdaily stability, intradaily variability, and relative amplitude. Birthweight was mother-reported and 3mon infant weight was measured with a Seca scale. Weight-for-age Z-scores (WAZ) by infant sex were computed based upon World Health Organization growth charts and the change difference between timepoints was the primary outcome. Regression models adjusting for birth WAZ examined the relationships between CRA metrics at eight weeks with change in WAZ from birth to 3mo. Results At eight weeks, mean±SD CRA metrics were as follows: 24hr autocorrelation of 0.25±0.03, mesor of 115.6±14.7, amplitude of 68.1±18.3, goodness-of-fit R2 of 0.42±0.10, acrophase of 14:12±1:42, interdaily stability of 0.57±0.12, intradaily variability of 0.93±0.19, and relative amplitude of 0.61±0.11. Mean birth WAZ and change in WAZ from birth to 3mon were 0.39±0.73 and -0.57±0.77, respectively. After adjusting for birth WAZ, in separate models, greater mesor (R2 Change=0.10, β=-0.32, p=0.03), amplitude (R2 Change=0.11, β=-0.34, p=0.03), and goodness-of-fit R2 (R2 Change=0.10, β=-0.32, p=0.04) were significantly associated with less change in WAZ from birth to 3mon. Conclusion Among relatively healthy, full-term infants born of normal weight, greater 24hr circadian rest-activity rhythmicity achieved by 8 weeks was associated with slower rate of weight gain across the newborn stage. Promoting behaviors and environmental cues from parents that strengthen early circadian rhythmicity in their infants may promote healthy weight trajectories. Support (if any) NIH/NHLBI R01HL147931

Introduction Infant sleep is influenced by biopsychosocial factors. However, the influences of early parental sleep quality and parent-infant bonding on infant sleep development are underexplored. This study aimed to examine the relationships between early maternal sleep quality and mother-infant bonding at 8 weeks postpartum, and infant bedtime difficulty at 3 months postpartum. Methods This study is a secondary analysis from the Snuggle Bug/Acurrucadito Study, an observational, longitudinal cohort study investigating the associations between 24-hr sleep-wake patterns, gut microbiome, and weight development among infants. Mothers (n=60, 31.5±5.4y, 66.3% married, 40.8% Hispanic, 41.5% < bachelor’s degree) and their full-term (≥37wk), singleton infants without major complications were recruited from Phoenix, Arizona metropolitan area. At 3 and 8 weeks, and 3 months of infant age, mothers completed the Pittsburgh Sleep Quality Index (PSQI, range:0-21, higher scores indicate worse sleep quality), and reported on infant bedtime difficulty, using a 5-point Likert scale (range:1-5) with higher scores indicating greater bedtime difficulty. Mother-infant bonding was measured by the Postpartum Bonding Questionnaire (PBQ, range:0-125) at 8-week age, with higher scores indicating greater bonding problems. Based on the Transactional Model of Infant Sleep, path analyses were conducted to identify the direct effect of 8-week PSQI scores, and indirect effects of 8-week PBQ total scores and 8-week bedtime difficulty on 3-month bedtime difficulty, using z scores for all variables and the 3-week bedtime difficulty as a covariate. Results At 8 weeks postpartum, the means of PSQI, PBQ, and bedtime difficulty were 5.8±2.6, 5.3±4.7, and 2.4±1.0, respectively. Bedtime difficulty at 3 months was 2.0±1.0. After adjusting for the 3-week bedtime difficulty, the 8-week maternal sleep quality was not directly associated with 8-week (β=.005, 95%CI [-0.31, 0.32]) or 3-month infant bedtime difficulty (β=-0.14, 95%CI [-0.43, 0.14]), whereas 8-week mother-infant bonding significantly mediated the relationship between 8-week maternal sleep quality and 3-month infant bedtime difficulty (β=0.1, 95%CI [0.02, 0.22]). Conclusion This study highlighted that early maternal sleep may disrupt early mother-infant bonding, which, in turn, may increase infant bedtime difficulty later in development. Future research should investigate how best to support healthy family sleep and bonding relationships. Support (if any) NIH/NHLBI R01HL147931

Introduction Exclusively breastfed (EBF) newborns wake more often at night than partially breastfed, or exclusively formula fed (EFF) newborns. Contextual factors during the first weeks of life related to these associations are understudied. We examined relationships among post-birth experiences, objectively-estimated sleep-wake patterns, and feeding practices through three weeks post-delivery. Methods English or Spanish speaking mothers (n=20) and their full-term (≥37wk), singleton infants were recruited from Phoenix, Arizona. Mothers were 32.7±5.1y, 30.0% identified as Hispanic, 20.0% with < high school degree, and 15.0% were enrolled in the federal Women, Infants, and Children program. Infants were born normal weight (2500-4000g) and without major complications. At three weeks post-delivery, infants wore a Micro Motionlogger (Ambulatory Monitoring Inc.) on their left ankle for five 24hr periods at three weeks of age. Mothers completed an accompanying sleep diary and an adapted Infant Feeding Practices Study-II questionnaire. Pearson correlations and t-tests examined relationships between nocturnal sleep-wake patterns and feeding practices at birth and 3-weeks post-delivery. Results At birth, all mothers attempted breastfeeding, 40.0% of infants received formula, and mean time for milk to come in was 2.7 days (range: 1-4). At three weeks, one mother was EFF, 55.5% (n=11) were EBF, and 40.0% (n=8) were mixed feeding. Infant sleep-wake patterns included midpoint of 2:40±1:01, long wake episode (≥5min) frequency of 5.8±2.3, longest sleep bout duration of 127.2±34.9min, WASO of 124.1±54.3min, and TST of 434.7±79.7min. Breastmilk feeding frequency was positively related to long wake episode frequency (r=.49, p=0.03) and WASO (r=.47, p=0.04), and negatively related to longest sleep bout (r=-.59, p=0.006). Formula feeding frequency was positively related to longest sleep bout (r=.58, p=0.007). Greater time for milk to come in was positively related to long wake episode frequency (r=.53, p=0.02) and WASO (r=.56, p=0.01), and negatively related to longest sleep bout (r=-.47, p=0.04). Receiving formula in the hospital was associated with later sleep midpoint (t[18]=3.2, p=0.005), regardless of current formula feeding. Conclusion Feeding experiences and ability to breastfeed during the first few days of life may play a role in the quality and patterning of actigraphy-estimated sleep among newborns. Future research should investigate whether these associations persist into later infancy. Support (If Any) National Institutes of Health / National Heart, Lung, and Blood Institute R01 HL147931

Introduction Increased sleep problems in adults have been repeatedly reported during the COVID-19 pandemic. However, infant sleep was understudied. We aimed to examine the relationships between the impact of the COVID-19 pandemic, parent insomnia, infant temperament, and infant sleep during the COVID-19 pandemic. Methods Parents from the Phoenix metropolitan area with a full-term healthy infant ( Results The parent sample was predominantly female (94.3%), identified as White (72.9%), had obtained a bachelor’s degree or above (71.5%), was married or in a domestic partnership (98.6%), and had household incomes > US$70,000 (57.1%). More than one third (35.7%) experienced insomnia symptoms. The means of CEFIS, ISI, IBQ-R subscale Negative Affect, and BISQ-R scores were 29.3±9.5, 8.7±5.2, 4.1±1.1, and 68.8±12.7, respectively. After adjusting for infant age, the COVID-19 related family impact was not directly associated with BISQ-R scores, whereas parent ISI scores (β=-0.11, 95%CI [-.25, -.01]) and infant IBQ-R Negative Affect scores (β=-0.10, 95%CI [-.25, -.002]) significantly mediated the relationship. Conclusion The study highlighted the indirect effects of parent insomnia symptom severity and infant negative affect on infant sleep from the family impact of the COVID-19 pandemic. Future research should investigate how best to support healthy sleep for families during global crises. Support (If Any)