The healthy human infant tends to sleep in the prone rather than the supine position

Death from Failed Protection? An Evolutionary-Developmental Theory of Sudden Infant Death Syndrome

Sudden infant death syndrome (SIDS) has been mainly described from a risk perspective, with a focus on endogenous, exogenous, and temporal risk factors that can interact to facilitate lethal outcomes. Here we discuss the limitations that this risk-based paradigm may have, using two of the major risk factors for SIDS, prone sleep position and bed-sharing, as examples. Based on a multipronged theoretical model encompassing evolutionary theory, developmental biology, and cultural mismatch theory, we conceptualize the vulnerability to SIDS as an imbalance between current physiologic-regulatory demands and current protective abilities on the part of the infant. From this understanding, SIDS appears as a developmental condition in which competencies relevant to self-protection fail to develop appropriately in the future victims. Since all of the protective resources in question are bound to emerge during normal infant development, we contend that SIDS may reflect an evolutionary mismatch situation-a constellation in which certain modern developmental influences may overextend the child's adaptive (evolutionary) repertoire. We thus argue that SIDS may be better understood if the focus on risk factors is complemented by a deeper appreciation of the protective resources that human infants acquire during their normal development. We extensively analyze this evolutionary-developmental theory against the body of epidemiological and experimental evidence in SIDS research and thereby also address the as-of-yet unresolved question of why breastfeeding may be protective against SIDS.

A proof-of-concept study to construct Bayesian network decision models for supporting the categorization of sudden unexpected infant death

Sudden infant death syndrome (SIDS) remains a leading cause of infant death in high-income countries. Supporting models for categorization of sudden unexpected infant death into SIDS/non-SIDS could reduce mortality. Therefore, we aimed to develop such a tool utilizing forensic data, but the reduced number of SIDS cases renders this task inherently difficult. To overcome this, we constructed Bayesian network models according to diagnoses performed by expert pathologists and created conditional probability tables in a proof-of-concept study. In the diagnostic support model, the data of 64 sudden unexpected infant death cases was employed as the training dataset, and 16 known-risk factors, including age at death and co-sleeping, were added. In the validation study, which included 8 new cases, the models reproduced experts’ diagnoses in 4 or 5 of the 6 SIDS cases. Next, to confirm the effectiveness of this approach for onset prediction, the data from 41 SIDS cases was employed. The model predicted that the risk of SIDS in 0- to 2-month-old infants exposed to passive smoking and co-sleeping is eightfold higher than that in the general infant population, which is comparable with previously published findings. The Bayesian approach could be a promising tool for constructing SIDS prevention models.

Does the prone sleeping position affect the intracranial dural venous flow?

PURPOSE

There are few studies documenting the effect of posture on intracranial dural venous flow. The aim of the present study was to explore alterations caused by the prone position using magnetic resonance (MR) venography.

METHODS

A total of eight patients (five men and three women) underwent non-contrast MR venography in both supine and prone positions.

RESULTS

In the prone position, an increase in intracranial dural venous flow was found in all patients in the non-dominant transverse and sigmoid sinuses. An increase in venous flow to the straight sinus was observed in 75% of the patients. Flow to the superior ophthalmic vein decreased in three patients. No postural flow alterations were observed in any of the patients in the superior sagittal, dominant transverse, and sigmoid sinuses.

CONCLUSION

Based on results of the study, in the prone sleeping position, part of the intracranial venous flow may be preferentially drained through the straight and non-dominant transverse sinuses.

Proposal for mechanisms of protection of supine sleep against sudden infant death syndrome: an integrated mechanism review

Supine sleep decreases sudden infant death syndrome (SIDS) incidence, however the mechanisms for this are unclear. The triple risk model for SIDS requires that one or more underlying abnormalities of breathing or autonomic control are present; these are rare, but brainstem defects are found in most SIDS cases. Supine sleep increases sympathetic nervous system tone, and level of state organization, and may therefore act as a stressor. This is evidenced by physiological arousal, and by delayed neurodevelopment in supine compared to prone sleepers. It is argued here that prone sleep position is the biological normative standard in healthy infants, supporting autonomic regulation. During rapid eye movement (REM) sleep (and other circumstances), a parasympathetic-mediated adverse autonomic event (AAE) may be spontaneously triggered. In healthy infants, gasping initiates autoresuscitation and recovery.

HYPOTHESIS

The underlying vulnerability to SIDS is specific to autoresuscitation from an AAE, the initial serotonin-dependent gasp is commonly compromised. Serotonin metabolism defects also influence sleep architecture, increasing the likelihood of AAE. The mechanism whereby supine sleep decreases SIDS may therefore be a stressor effect, disturbing sleep architecture to decrease REM and AAEs, and increasing sympathetic tone, which may prevent and counteract the purely parasympathetic-mediated AAE, thereby decreasing the risk of SIDS.

The influence of wakeful prone positioning on motor development during the early life

OBJECTIVE

The "Prone to Play" campaign was proposed and has been ongoing since 2001, but the causal and dosage effects of wakeful prone positioning on motor development are still unclear. The purpose of this longitudinal cohort study was to investigate the effects of prone wakeful positioning at 3 to 6 months of age on motor development during the 6 to 24 months age bracket.

METHODS

Two hundred eighty-eight full-term newborns were recruited at birth and followed up at 4, 6, 12, and 24 months of age respectively. Data on experience, duration, and preference of prone wakeful positioning were collected at 4 and 6 months of age. The acquisition ages of prone specific and nonprone milestones were collected and analyzed to evaluate the impact of wakeful prone positioning on motor development during early life. Gross motor developmental quotients (GMDQ) and fine motor developmental quotients (FMDQ) of the Comprehensive Developmental Inventory for Infants and Toddlers were assessed at ages 6 and 24 months.

RESULTS

The prone duration significantly affected the acquisition ages of 3 prone specific milestones (rolling, crawling-on-abdomen, crawling-on-all-fours) and sitting; without affecting the other 2 nonprone specific milestones (walking and transferring objects), GMDQs and FMDQs. The infants of prone preference achieved prone specific milestones earlier than those of nonprone preference. The prone experience affected the crawling-on-abdomen acquisition age, but not the other motor outcomes.

CONCLUSION

Wakeful prone positioning promotes prone-specific motor milestones in early infancy. "Prone to play for a certain amount of time in an interactive and supervised environment" might be advocated.