Longitudinal Study of Sleep Behavior in Normal Infants during the First Year of Life

Abstract

Study Objectives: To longitudinally examine sleep patterns, habits, and parent-reported sleep problems during the fi rst year of life. Methods: Seven hundred four parent/child pairs participated in a longitudinal cohort study. Structured interview recording general demographic data, feeding habits, intercurrent diseases, family history, sleep habits, and parental evaluation of the infant's sleep carried out at 1, 3, 6, 9, and 12 months Results: Nocturnal, daytime, and total sleep duration showed a high inter-individual variability in the fi rst year of life associated with changes in the fi rst 6 months and stability from 6 to 12 months. Bedtime was at around 22:00 and remained stable at 6, 9, and 12 months of age. Approximately 20% of the infants had more than 2 awakenings and slept more often in the parent bed. Nearly 10% of the infants were considered as having a problematic sleep by parents and this signifi cantly correlated with nocturnal awakenings and diffi culties falling asleep. Conclusions: Sleep patterns change during the fi rst year of life but most sleep variables (i.e., sleep latency and duration) show little variation from 6 to 12 months. Our data provide a context for clinicians to discuss sleep issues with parents and suggest that prevention efforts should focus to the fi rst 3-6 months, since sleep patterns show stability from that time point to 12 months. S C I E N T I F I C I N V E S T I G A T I O N SS leep patterns and sleep structure show signifi cant changes during the fi rst year of life; the circadian rhythm is not established in the fi rst months, and sleep is distributed throughout the day and night with a basic rest/activity cycle, similar to that of fetal life. At 1-2 weeks of age the fetal circadian rhythms starts to fade away and, at 1-2 months, the circadian activity rhythm develops with colic as the fi rst sign of circadian rhythmicity; at 3-4 months of age, infants are entrained to the 24-h cycle and melatonin production is stable. At 6-9 months, wakefulness increases, daytime naps are established, and fi nally, at 12 months 70% to 80% of infants sleep mostly at night. 2 demonstrated that daytime sleep is mostly determined by maturation (age), whereas nocturnal sleep is better predicted by ecological factors. More specifi cally, studies of infant sleep correlates showed that intense parental involvement and reduced self-soothing skills may interfere with nighttime sleep consolidation.2,3 Not only major developmental steps are determined by the interaction between maturational processes and ecological factors; sleep-wake patterns are also heavily infl uenced by biological and cultural factors, and therefore the concept of "normal sleep" varies according to cultural BRIEF SUMMARYCurrent Knowledge/Study Rationale: To our knowledge, most of the data on the sleep pattern development in the previous reports were derived from longitudinal studies designed to collect different information but not exclusively intended to assess sleep structure and ecology. Our study represents the fi r...

Infant sleep problems: The sleep characteristics of the “Don't Know” response

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