The results of this pilot study provide initial evidence for effects of behavioral interventions delivered during the first year after birth on weight status at 1 year. As predicted, the behavioral interventions produced differences in sleep duration and feeding frequency among breastfed infants in the first months after birth and later in infancy affected the timing of introduction and acceptance of solid foods. The results at 1 year provide preliminary evidence that early-life differences among groups in sleeping and feeding may mediate differences in weight status at 1 year. These findings are potentially encouraging from an obesity prevention perspective because early-life growth patterns have increasingly been associated with both childhood and adult obesity (8
) as well as risk for hypertension (54
), coronary heart disease (58
), and type 2 diabetes mellitus (60
It is notable and not surprising that infants who received single interventions did not differ from the control group with regard to weight status at 1 year or growth over the study period. During the first year after birth the choice to breast or formula feed and the use of feeding to soothe, as well as later choices regarding the timing of the introduction of solids and the introduction of table foods all have been linked to differences in infant weight status (62
). It is likely that multiple interventions and consistent reinforcement of their messages through the various stages of infant development are necessary to maintain long-term and sustained protection from obesity.
The interaction between feeding mode (predominantly breast milk or not predominantly breast milk) and the effect of the study interventions is also noteworthy. As found in this study, breastfeeding has been shown to have a modest protective effect against obesity development, but it has also been associated with shorter sleep duration when breastfed infants are compared with formula-fed infants (69
). It is therefore paradoxical that shorter sleep duration has been associated with obesity, even among infants. The findings of this study for breastfed infants are provocative and hypothesis generating. Our findings, showing increased sleep duration among breastfed infants suggests that increasing sleep duration may confer additional protection against obesity for these infants. Alternatively, the inability to lengthen sleep duration among those not predominantly breastfeeding suggests that alternate strategies should be considered for this population already at risk for later obesity. The results for feeding frequency showing that the “Soothe/Sleep” intervention also reduced the number of nocturnal and total daily feedings for breastfed infants, suggest the possibility that reduced feeding frequency, rather than increased sleep duration may have contributed to the differences in growth noted among groups.
There are several limitations to this pilot study. First, our sample was limited to first-time mothers who intended to breastfeed, and was fairly homogeneous with limited minority participation making it difficult to generalize the findings to other populations, particularly those known to be at higher risk for obesity. Second, we obtained evidence of positive effects of our behavioral interventions designed to increase sleeping and reduce feeding frequency only among those dyads who continued to breastfeed. Because all mothers recruited originally intended to breastfeed, it is also possible that the mothers who discontinued breastfeeding differed in their ability to adhere to study interventions and/or requirements whether due to personal or environmental factors. The study population was also recruited from a single hospital with English speaking mothers who, as a group, were relatively well educated. Next, the duration of follow-up was relatively short. It will be important to follow infants longitudinally to see whether long-term obesity risk can be affected by interventions delivered during infancy. Fourth, the attrition rate for this study affects the interpretation of the findings particularly because the largest number of dropouts came from the dual intervention group. The birth of a first child and caring for the infant can be overwhelming for new parents, and although we noted effects of our interventions, the high participant burden and intensity of the interventions likely contributed to attrition. Alternatively, the added attention received by those receiving study interventions could have affected the outcomes compared with control participants who did not receive home visits of equal time duration or intensity. Finally, we do not have adequate data to assess the extent to which parents’ implementation of the “Soothe/Sleep” intervention may have affected its impact. Future evaluations should better measure the adherence to intervention components.
Despite the limitations, these findings suggest that multi-component interventions may potentially be successful at helping infants achieve a healthy growth trajectory. The secondary outcomes related to each intervention (sleep duration, nocturnal feeding, acceptance of solid foods) reveal that behaviors previously associated with differences in weight gain in infancy and with long-term obesity risk can be influenced. Because infancy represents a critical period of rapid growth and developmental plasticity with long-lasting metabolic and behavioral consequences, successful interventions may have highly meaningful long-term effects for the prevention of obesity and its comorbidities.