If you have not already done so, please read Blog Posts 1 through 5 that describe how sleep is important and beneficial. I will post specific information for parents and children based on my book, “Healthy Sleep Habits, Happy Child.” Please do not be put off by my book’s length. This is a reference book. Read only the topic of interest to you.
I discovered an association between temperament characteristics and sleep. In my study of sixty 4- to 5-month-old infants, the infants rated as having a difficult temperament had average sleep times substantially less than the infants rated as easy (12.3 versus 15.6 hours). Also, four of the individual temperament traits (mood, adaptability, rhythmicity, and approach/withdrawal) were each highly associated with total sleep duration. When this study was extended to include 105 infants, those infants with difficult temperaments slept 12.8 hours and those with easy temperaments slept 14.9 hours. This observation was subsequently confirmed in a study of Chinese-American infants of similar age but with different parenting practices.
It thus appears that infants who have a difficult temperament have briefer total sleep durations when assessed at 4–5 months of age regardless of differences in parenting practices. In addition to short sleep durations, a study of children between 6 and 36 months showed that more fragmented sleep is associated with a more difficult temperament. Also, a Canadian study showed that sleep difficulties starting around 5 months persist at age 6 years and that “sleep difficulties likely are part of the difficult temperament profile.” A Swedish study of children, over the same age range, also noted stability over time of frequent night wakings and low quality of sleep.
Perhaps the temperament-sleep association at 4–5 months is caused by biological features. For example, a continuation of sleep issues in a post-colic infant (who no longer is prone to spells of fussing or crying). Alternatively, the association between temperament and sleep may reflect parent issues such as maternal anxiety resulting in the inability to establish healthy sleep habits. Or both (Blog Posts 39–45).
In support of a biological or baby-driven path, a study of about one thousand Canadian families, temperament assessments were performed at age 5 and 17 months. “Maladaptive parental behaviors” were recorded at 29 and 41 months and included mother’s presence until the child fell asleep, giving food/drink after child wakes in the night, and co-sleeping in the mother’s bed after awakening at night. Analysis of the data “support the suggestion that difficult temperament is the original context within which sleep disturbances arise . . . when controlling for early sleep problems, difficult temperament remained predictive only of shorter total sleep time [at age 6 years].” Their findings further “suggest that sleep difficulties likely are part of the difficult temperament . . . [and maladaptive parental behaviors] develop in reaction to prior sleep problems [emphasis added].”
Support for a persistent parent-driven path between temperament and sleep is based on a study by Dr. Marcia Keener in which objective measures of sleep/wake organization, derived from time-lapse video recordings, were compared with parental perceptions of infant temperament at 6 months of age. Dr. Keener stated that “infants considered [temperamentally] easy have longer sleep periods and spend less time out of the crib for caretaking interventions during the night.” Her analysis also led her to the conclusion that night waking is caused by parental rather than biological factors. This observation of increased time out of the crib for temperamentally more difficult children at 6 months is similar to the observation that increased night waking occurs in formerly colicky infants at 4, 8, and 12 months, and it is also similar to the observation that mothers with depressive symptoms unnecessarily attend to their babies by removing them from the crib more often than mothers without these symptoms (Blog Post 45).
The framing of the question as to whether biological factors in the baby (such as colic or difficult temperament) or parenting issues (such as maternal anxiety or depression) cause persisting sleep problems may be fundamentally incorrect. Genetic influences regarding temperament, sleep duration (Blog Post 14), and screen time (Blog Post 22) may play a role contributing both to baby and parent behavior. In fact, a careful analysis of forty-five longitudinal studies of sleep behavior in children 4–12 years found only 12 studies that were rated as “high quality.” Examining these 12 studies, the researchers looked at 61 possible determinants for sleep duration. Only 3 determinants showed evidence for causing short sleep duration: A past history of short sleep duration, a difficult temperament and more screen time.
But genetics is not destiny. I believe that sleep modulates temperament (Blog Post 48), so it is important to get a handle on your child’s sleep early to influence temperament and thus mitigate adverse sleep outcomes associated with a difficult temperament.
(To be continued.)