Sleep and temperament in 12 months old infants

INTRODUCTION: Several factors contribute to different sleep behaviors in infancy, including infant characteristics, parent-infant dynamics, as well as environmental characteristics. Previous studies have shown that difficult temperament appears related to more sleep awakenings and sleep problems in general. Nonetheless, results are far from being conclusive due to limitations of previous studies, including the reliance on parental reports for sleep metrics, small sample sizes and use of heterogeneous questionnaires to evaluate temperament. In this study we propose to address this knowledge gap by investigating the relationship between infant sleep and temperament at 12 months of age, relying on objective sleep metrics. METHODS: Caregivers of 623 infants aged 9-13 mos (10.3±1.1, 52% females) were recruited among users of Nanit baby-monitor in the United States. Caregivers completed the Brief Infant Sleep Questionnaire (BISQ-R) and the Infant Behavior Questionnaire (IBQ-R). Objective infant sleep metrics were obtained from the Nanit (1 week). Sleep metrics analyzed were: total sleep time, number of night-wakings, sleep efficiency, bedtime, wake up time, time awake at night and parent interventions. Person correlation between each sleep metric and IBQR global score (Orienting/ Effortful control; Surgency/extraversion; Negative Affectivity) and subscales were calculated. RESULTS: Higer infant negative affectivity was significantly associated with shorter total sleep time (r=-0.25, p<0.01), lower sleep efficiency (r=-0.13, p<0.01), longer time awake at night (r=0.1, p<0.001), later bedtime (r=0.12, p<0.01), more night-wakings (r=0.12, p<0.01) and parental interventions (r=0.17, p<0.01). Although Orienting/ Effortful control and Surgency/Extraversion global scores were not significantly associated with any sleep metric, some of their subscales were. Lower soothability was associated with shorter total sleep time (r=-0.09, p<0.05), poorer sleep efficiency (r=-0.1, p<0.01), and less parental interventions (r--0.08, p<0.05). Higher Perceptual Sensitivity was associated with more night awakenings (r=0.13, p<0.01), and high approachability to later bedtime (r=0.09, p<0.05). CONCLUSIONS: This study adds to the current literature on sleep and development thanks to a large sample size and objective sleep metrics. Our findings support previous research, highlighting that negative affectivity is associated with poor sleep across multiple domains while sleep disturbances may predict internalizing problems.