Association Between Sleep Position and Early Motor Development
Majnemer A, Barr RG
J Pediatr. 2006;149(5):623-629
Summary
While emphasis on the supine sleeping position has been associated with marked decreases in rates of sudden infant death syndrome, some earlier reports suggested that the supine sleeping position might also be associated with delays in some motor activities when supine-sleeping infants were < 6 months old.
This study utilized formal and validated measures of early motor development (rather than parental report or office "screening" for gross motor delays) to compare the developmental motor milestones of prone-sleeping vs supine-sleeping 4- and 6-month-old infants. The authors identified subjects from community practices and evaluated children at either 4 or 6 months (no subject was evaluated at both ages). After consent in the community practice, parents completed surveys that collected demographic and some maternal medical history, including the infant's consistent sleep position.
All infants were at least 38 weeks' gestation and had no medical problems that would complicate the analyses. In addition, the infants did not attend daycare (to avoid variation in sleep position by different caregivers). The authors also selected only white children in an attempt to eliminate race and cultural factors. The infants were then examined within 1 week by an occupational and physical therapist. The physical and occupational therapists were masked to infant sleep position and the true nature of the study and examined the patients on separate occasions. The physical therapist completed the Alberta Infant Motor Scale (AIMS) while the occupational therapist completed the Peabody Developmental Motor Scales (PDMS). The infants were reevaluated at 15 months by the occupational therapist only. For 3 days after enrollment, the parents completed a diary to record the infant's position while awake and time spent in each position.
Seventy-one supine infants were evaluated at 4 months along with 12 prone-sleeping comparison infants. For the assessment of 6-month-olds, there were 50 supine-sleeping infants and 22 prone-sleeping infants. At 4 months of age, there was no statistically significant difference between the 2 groups with regard to AIMS percentile score (47.7 for supine group and 54.2 for prone group). There was a significantly higher "prone raw score" in the prone-sleeping group at this age, however, meaning that the infants did better on testing done in the prone position. Of note, 8.4% of the supine-sleeping 4-month-olds had reached the AIMS milestone of "extended arm support" compared with 27.3% of the prone-sleeping infants (P < .05).
At 4 months, there were no differences in PDMS measures for gross or fine motor. None of the children were below the respective clinically relevant cutoffs for the 2 tests, so none were technically "delayed." At 6 months, however, the supine-sleeping group performed at a significantly lower level on all but 1 measure. For example, the AIMS percentile score was 44.5% for the supine group vs 60% for the prone-sleeping group. Twenty-two percent of the supine-sleeping infants would have met criteria for gross motor delay at 6 months. For PDMS measures, the supine-sleeping group had a lower Gross Motor Quotient, but the Fine Motor Quotient was similar for the 2 groups. At 15 months, the groups were similar with regard to the PDMS quotient scores, but the supine-sleeping group was approximately half as likely to achieve "walking up stairs" and slightly less likely to be "walking" compared with the prone-sleeping group. In regression analyses, the sleep position remained significantly associated with AIMS and PDMS scores at both the 4- and 6-month evaluations. This relationship persisted at 15 months.
The authors did not detect significant differences in daytime positioning between the 2 groups, but percentage of time in prone daytime position did correlate with the outcome measures, and this relationship also held up in multivariate analyses. The authors concluded that supine-sleeping infants as well as infants with less prone positioning while awake experience early lags in attainment of motor milestones.
Viewpoints
Reviewer comment: I personally had to help my own 3 children "catch up" in the weeks preceding their respective 4-month-old health maintenance visits, so I'm glad to see that my experience was not so unusual. The lessons from this article are that the delays experienced by supine-sleeping infants are real even if they might not always reach clinical significance. In addition, the daytime positioning can either exacerbate (if there is not enough prone time) or ameliorate (with more prone time) the supine-associated delays. In an associated commentary, James Kemp notes that these findings and reassurances should not be extended in any way to nonhealthy or premature infants, and that is always a point worth emphasizing.
Abstract URL:http://www.medscape.com/medline/abstract/17095331