Wednesday, August 20, 2008

Post-natal Slow Wave Sleep Inhibition and the SIDS "Back to Sleep" Campaign

In human infants sleep develops rapidly during early development. This development includes an increase in non-rapid eye movement (NREM) sleep which is also called Quiet Sleep (QS) during the first 12 months of life in association with a decrease in rapid eye movement (REM) sleep which is also known as Active Sleep (AS) [1-3]. In addition, slow wave sleep (SWS) which consists of Stage 3 and Stage 4 NREM sleep appears at 2 months of age [4-7].


In a currently utilized model that explains the process in which slow wave sleep is involved in memory consolidation the hippocampus acts as a temporary storage facility for new memories which are then transferred to the neocortex during slow wave sleep (SWS) [8]. In this model, acetylcholine acts a feedback loop inhibitor inside the hippocampus during REM sleep and wakefulness. The activity during the high cholinergic wakefulness period is believed to provide an environment which allows for the encoding within the hippocampus of new declarative memories. The low cholinergic environment during SWS is thought to then allow these memories to be transferred from the temporary storage of the hippocampus to their permanent storage environment in the neocortex and for memory consolidation [9, 10].


A significant way of decreasing slow wave sleep in infants is by changing their sleeping position from prone to supine. It has been shown in studies of preterm infants [11, 12], full-term infants [13, 14], and older infants [15], that they have greater time periods of quiet sleep and also decreased time awake when they are positioned to sleep in the prone position. In both human infants and rats, arousal thresholds have been shown to be at higher levels in the EEG delta range [16-18]. In addition, Epidemiological studies strongly associate the prone sleep position to a higher risk of SIDS for infants [19-21]. Based upon the epidemiological evidence and studies of sleep physiology, the American Academy of Pediatrics developed a supine sleep position SIDS risk reduction strategy which is based on decreasing arousal thresholds and decreasing quiet sleep for infants [22].


In 1992 [23], a SIDS risk reduction strategy based upon lowering arousal thresholds during SWS was implemented by the American Academy of Pediatrics (AAP) which began recommending that healthy infants be positioned to sleep on their back (supine position) or side (lateral position), instead of their stomach (prone position), when being placed down for sleep. The AAP’s 1992 recommendations were announced five years after the Netherlands had started it’s infant supine sleep position campaign in 1987 [24]. The Netherlands recommendations were followed by infant supine sleep position campaigns in the United Kingdom, New Zealand, and Australia in 1991, the U.S. and Sweden in 1992, and Canada in 1993 [25, 26]. In 1994 [27], a number of organizations in the United States combined to further communicate these non-prone sleep position recommendations and this became formally known as the “Back To Sleep” campaign. In 1996 [28], the AAP further refined its sleep position recommendation by stating that infants should only be placed to sleep in the supine position and not in the prone or lateral positions.


In 1992, the first National Infant Sleep Position (NISP) Household Survey [29] was conducted to determine the usual position in which U.S. mothers placed their babies to sleep. According to the 1992 NISP survey, 13.0% of U.S. infants were positioned in the supine position for sleep [30]. According to the 2006 NISP survey 75.7% of infants were positioned in the supine position to sleep [31]. Mothers that are younger and those that are less well-educated are more likely to put their infants to sleep in the prone position [32-34].


Since 1998 there have been three studies published which show that infants placed to sleep in the supine position lag in motor skills, social skills, and cognitive ability development when compared to infants who sleep in the prone position [35-37]. None of these three studies analyzed children older than 18 months of age and the authors of all three studies considered the lags at less than 18 months of age to be temporary and do not think that the supine sleep recommendations should be changed. Placing infants in the prone position while they are awake has been recommended to offset the motor skills delays associated with the supine sleep position [38] but positioning the infant prone while awake will not impact the amount of slow wave sleep [39-43].


SIDS deaths in the U.S. decreased from 4,895 in 1992 to 2,247 in 2004 [44]. But, during a similar time period, 1989 to 2004, SIDS being listed as the cause of death for sudden infant death (SID) decreased from 80% to 55% [45]. In addition, maternal pregnancy smoking rates decreased by 38% during a similar time period, 1990-2002 [46]. According to Dr. John Kattwinkel, chairman of the Center for Disease Control (CDC) Special Task Force on SIDS "A lot of us are concerned that the rate (of SIDS) isn't decreasing significantly, but that a lot of it is just code shifting” [47]. Considering that the original non-prone sleep recommendations were implemented 16 years ago in the U.S. and that human development is not always linear it may be time to re-evaluate the long-term impact of the “Back to Sleep” Campaign on motor skills, social skills, and cognitive ability.




References:
1. Louis J, Cannard C, Bastuji H, and Challamel MJ. Sleep ontogenesis revisited: a longitudinal 24-hour home polygraphic study on 15 normal infants during the first two years of life. Sleep 20: 323–333, 1997
2. Navelet Y, Benoit O, and Bouard G. Nocturnal sleep organization during the first months of life. Electroencephalogr Clin Neurophysiol 54: 71–8, 1982.
3. Roffwarg HP, Muzio JN, and Dement WC. Ontogenetic development of the human sleep-dream cycle. Science 152: 604–619, 1966.
4. Anders TF and Keener M. Developmental course of nighttime sleepwake patterns in full-term and premature infants during the first year of life. I. Sleep 8: 173–92, 1985.
5. Bes F, Schulz H, Navelet Y, and Salzarulo P. The distribution of slow-wave sleep across the night: a comparison for infants, children, and adults. Sleep 14: 5–12, 1991.
6. Coons S and Guilleminault C. Development of sleep-wake patterns and non-rapid eye movement sleep stages during the first six months of life in normal infants. Pediatrics 69: 793–798, 1982.
7. Fagioli I and Salzarulo P. Sleep states development in the first year of life assessed through 24-h recordings. Early Hum Dev 6: 215–228, 1982.
8. Hasselmo, M.E. 1999. Neuromodulation: Acetylcholine and memory consolidation. Trends Cogn. Sci. 3: 351–359.
9. Buzsáki, G. 1989. Two-stage model of memory trace formation: A role for “noisy” brain states. Neuroscience 31: 551–570.
10. Hasselmo, M.E. 1999. Neuromodulation: Acetylcholine and memory consolidation. Trends Cogn. Sci. 3: 351–359.
11. Myers MM, Fifer WP, Schaeffer L, et al. Effects of sleeping position and time after feeding on the organization of sleep/wake states in prematurely born infants. Sleep 1998;21:343–9.
12. Sahni R, Saluja D, Schulze KF, et al. Quality of diet, body position, and time after feeding influence behavioral states in low birth weight infants. Pediatr Res 2002;52:399–404.
13. Brackbill Y, Douthitt TC, West H. Psychophysiologic effects in the neonate of prone versus supine placement. J Pediatr 1973;82:82–4.
14. Amemiya F, Vos JE, Prechtl HF. Effects of prone and supine position on heart rate, respiratory rate and motor activity in full term infants. Brain Dev 1991;3:148–54.
15. Kahn A, Rebuffat E, Sottiaux M, et al. Arousal induced by proximal esophageal reflux in infants. Sleep 1991;14:39–42.
16. Ashton R. The influence of state and prandial condition upon the reactivity of the newborn to auditory stimulation. J Exp Child Psychol. 1973;15:315–327
17. Rechtschaffen A, Hauri P, Zeitlin M. Auditory awakening thresholds in REM and NREM sleep stages. Percept Motor Skills. 1966;22:927–942
18. Neckelmann D, Ursin R. Sleep stages and EEG power spectrum in relation to acoustical stimulus arousal threshold in the rat. Sleep. 1993; 16:467–477
19. Consensus: a scientific review of the association between prone sleeping position and sudden infant syndrome. J Paediatr Child Health 1991;27:323–4.
20. Dwyer T, Posonby AL, Newman NM, et al. Prospective cohort study of prone position and sudden infant syndrome. Lancet 1991;337:1244–7.
21. Mitchell EA, Tuohy PG, Brunt JM, et al. Risk factors of sudden infant death syndrome following the prevention campaign in New Zealand: a prospective study. Pediatrics 1997;100:835–40.
22. Kattwinkel J, Hauck F.R., Moon R.Y., Malloy M and Willinger M Infant Death Syndrome: In Reply, Bed Sharing With Unimpaired Parents Is Not an Important Risk for Sudden\Pediatrics 2006;117;994-996
23. Kattwinkel J, Brooks J, Myerberg D; American Academy of Pediatrics, Task Force on Infant Positioning and SIDS. Positioning and SIDS. Pediatrics. 1992;89:1120–1126
24. Högberg U, Bergström E. Suffocated Prone: The Iatrogenic Tragedy of SIDS. Am J Public Health. 2000;90:527–531 (103)
25. Högberg U, Bergström E. Suffocated Prone: The Iatrogenic Tragedy of SIDS. Am J Public Health. 2000;90:527–531 (104)
26. Rusen I, Shiliang L, Sauve R, Joseph K, Kramer M. Sudden infant death syndrome in Canada: Trends in rates and risk factors, 1985-1998. Chronic Diseases in Canada. 2005;24:1 (105)
27. U.S. Department of Human Services. "BACK TO SLEEP" CAMPAIGN SEEKS To Reduce Inicidence of SIDS In African American Populations PressRelease. http://www.hhs.gov/news/press/1999pres/991026.html Tuesday, Oct. 26, 1999
28. American Academy of Pediatrics Task Force on Infant Positioning and SIDS. Positioning and sudden infant death syndrome (SIDS): update. Pediatrics. 1996;98:1216-1218
29. National Institute of Child Health and Development (NICHD).SIDS Research. website.:http://www.nichd.nih.gov/publications/pubs/council_ppb_2004/sub8.cfm 08/28/2006
30. National Infant Sleep Position Household Survey. Summary Data 1992. http://dccwww.bumc.bu.edu/ChimeNisp/NISP_Data.asp updated: 09/04/07
31. National Infant Sleep Position Household Survey. Summary Data 2006. http://dccwww.bumc.bu.edu/ChimeNisp/NISP_Data.asp updated: 09/04/07
32. Willinger M, Hoffman HJ, Wu KT, et al. Factors associated with the transition to nonprone sleep positions of infants in the United States: The National Infant Sleep Position Study. JAMA. 1998;280:329–335
33. Bigger HR, Silvestri JM, Shott S, Weese-Mayer DE. Influence of increased survival in very low birth weight, low birth weight, and normal birth weight infants on the incidence of sudden infant death syndrome in the United States: 1985–1991. J Pediatr. 1998;133:73–78
34. Lesko SM, Corwin MJ, Vezina RM, et al. Changes in sleep position during infancy: a prospective longitudinal assessment. JAMA. 1998;280: 336–340
35. Dewey C, Fleming P, Golding J, the ALSPAC Study Team. Does the Supine Sleeping Position Have Any Adverse Effects on the Child? II. Development in the First 18 Months. Pediatrics. 1998;101:1-5
36. Majnemer A, Barr R. Influence of supine sleep positioning on early milestone acquisition. Developmental Medicine & Child Neurology. 2005;47:370-376
37. Davis B, Moon R, Sachs H, Ottolini M. Effects of Sleep Position on Infant Motor Development. Pediatrics. 1998;102:1135-1140
38. Majnemer A, Barr R. Influence of supine sleep positioning on early milestone acquisition. Developmental Medicine & Child Neurology. 2005;47:370-376
39. Myers MM, Fifer WP, Schaeffer L, et al. Effects of sleeping position and time after feeding on the organization of sleep/wake states in prematurely born infants. Sleep 1998;21:343–9.
40. Sahni R, Saluja D, Schulze KF, et al. Quality of diet, body position, and time after feeding influence behavioral states in low birth weight infants. Pediatr Res 2002;52:399–404.
41. Brackbill Y, Douthitt TC, West H. Psychophysiologic effects in the neonate of prone versus supine placement. J Pediatr 1973;82:82–4.
42. Amemiya F, Vos JE, Prechtl HF. Effects of prone and supine position on heart rate, respiratory rate and motor activity in full term infants. Brain Dev 1991;3:148–54.
43. Kahn A, Rebuffat E, Sottiaux M, et al. Arousal induced by proximal esophageal reflux in infants. Sleep 1991;14:39–42.
44. Bowman L, Hargrove T. Exposing Sudden Infant Death In America. Scripps Howard News Service. http://dailycamera.com/news/2007/oct/08/saving-babies-exposing-sudden-infant-death-in/
45. Bowman L, Hargrove T. Exposing Sudden Infant Death In America. Scripps Howard News Service. http://dailycamera.com/news/2007/oct/08/saving-babies-exposing-sudden-infant-death-in/
46. Centers for Disease Control. Smoking & Tobacco Use - Morbidity and Mortality Weekly Reports (MMWRs) – Smoking During Pregnancy – United States, 1990-2002 – October 7, 2004 / Vol. 53/ No. 39 http://www.cdc.gov/tobacco/data_statistics/MMWR/2004/mm5339_highlights.htm
47. Bowman L, Hargrove T. Exposing Sudden Infant Death In America. Scripps Howard News Service. http://dailycamera.com/news/2007/oct/08/saving-babies-exposing-sudden-infant-death-in/