Infants fed to sleep at 2 months wake up more often at 6 months

A 12-month longitudinal study found that infants who are put to bed with a bottle at 2 months of age tended to display more sleep problems at 6 months of age. They needed a longer time to fall asleep, spent more time awake, and woke up during the night more often. Mothers of infants who displayed more sleep problems at 6 months of age were more likely to keep putting them to bed with a bottle at 14 months of age. The paper was published in the Journal of Sleep Research.

Many infants have sleep problems, particularly in the first year of life. These include difficulty falling asleep, frequent or prolonged night wakings, short nighttime sleep duration, and an inability to soothe themselves back to sleep. These problems are important because they are linked to later risks for both child and family well-being.

Poor infant sleep has been associated with outcomes such as overweight, obesity, and difficulties in emotional and behavioral regulation. Sleep problems also affect parents, contributing to higher depressive symptoms, lower energy, and less adaptive parenting practices. Research suggests that infant sleep and parenting behaviors influence each other in a bidirectional, transactional way over time.

One parenting practice of interest is putting an infant to bed with a bottle, which is believed to interfere with the infant’s ability to self-soothe to sleep. Feeding infants to sleep is associated with shorter nighttime sleep duration, more frequent night wakings, and greater sleep fragmentation. Expert guidance therefore emphasizes putting infants to bed while drowsy but still awake, rather than using feeding as a sleep aid.

Providing a bottle at bedtime has also been identified as a feeding practice that promotes obesity, linking sleep routines to physical health outcomes. Poor infant sleep may, in turn, increase parents’ reliance on bottle-to-bed practices as a way to manage nighttime distress.

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Study author Esther M. Leerkes and her colleagues wanted to examine associations between putting the infant to bed with a bottle and maternal-reported infant sleep problems. They conducted a 12-month longitudinal study in which they followed a group of infants and their mothers from the infants’ 2nd month of life until the infants were 14 months old.

Pregnant women in their third trimester were recruited in and around Guilford County, North Carolina, to participate in the Infant Growth and Development Study. The primary goal of that larger study was to identify early life predictors of childhood obesity. Originally, 299 women were recruited. The average age of these mothers was approximately 30 years (mean age 29.71).

Data from participating women were collected when their infants were 2 months, 6 months, and 14 months old. 90% of these women provided data at the 2-month wave, 81% at 6 months, and 76% at 14 months.

Mothers reported how often they put their infant to bed with a bottle of formula, breast milk, juice, juice drink, or any other kind of milk by providing ratings on a 5-point scale. They reported infants’ sleep problems using the Brief Infant Sleep Questionnaire.

The study authors included data on maternal education, race, and their participation in the Women, Infant and Children Special Food Supplemental Program (WIC) in their analyses. They also controlled for maternal depressive symptoms, maternal sleep quality, breastfeeding status, and weekly work hours. WIC is a U.S. federal nutrition assistance program that provides supplemental foods, nutrition education, and health referrals to low-income pregnant women, new mothers, infants, and young children.

Results showed that infants who were put to bed with a bottle more frequently at 2 months of age tended to display more sleep problems at 6 months of age. They needed a longer time to fall asleep, spent more time awake at night, and had more frequent night wakings.

Mothers whose infants woke up more frequently and less time sleeping during the night at 6 months were more likely to be putting them to bed with a bottle at 14 months of age.

“In conclusion, putting infants to bed with a bottle and infant sleep problems influence one another across infants’ first year and into their second year. Given infant sleep problems are a predictor of maladaptive infant, parent and family outcomes, efforts to prevent parental use of this strategy are important to promote infant and parent well-being,” the study authors concluded.

The study contributes to the scientific knowledge about infant sleep patterns. However, it should be noted that both infants’ sleep quality and bottle-to-bed practices were reported by mothers, leaving room for reporting and common method bias to have affected the results.

The paper, “Transactional Associations Between Bottle to Bed and Infant Sleep Problems Over the First Year,” was authored by Esther M. Leerkes, Agona Lutolli, Cheryl Buehler, Lenka Shriver, and Laurie Wideman.