What is Sudden Infant Death Syndrome (SIDS)Sudden infant death syndrome has been defined as “the sudden death of an infant under one year of age, which remains unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene and review of the clinical history.” It occurs less frequently in the first month of life, the risk is highest between 2 and 4 months of age, decreasing thereafter. The boys are more affected as compared with the baby girls.. Almost 90% of the reported cases took place in the first six months of life.
Etiology of SIDSAnecdotal evidence suggests that some of the infant deaths are due to upper airway obstruction. Obstructive apnoea has been suggested as a possible reason for SIDS. Another group of investigators have shown that the hypoxanthine concentration was found to be raised in the vitreous humor of babies dying from SIDS. Hypoxanthine is a breakdown product of adenosine monophosphate, a catabolic process accelerated by hypoxia, providing supportive evidence that babies suffered from recurring hypoxia before death.
It has also been suggested that many infants die due to a viral upper respiratory tract infection, which may have led to hyperpyrexia and central apnoea causing SIDS. Another study claims that babies dying due to SIDS may have a defect of immune system. An increased concentration of IgG, IgM and may be IgA was reported in the lungs of these babies.
Autonomic impairment or immature cardiorespiratory autonomic control, and a failure of arousal responsiveness from sleep are also known to cause SIDS.
Increasingly developing research has shown that SIDS may be the consequence of a primary underlying genetic disorder, including inborn errors of metabolism (Especially fatty acid metabolism disorders), genetic defects of cardiac conduction and hypertrophic cardiomyopathies.
Risk factors for SIDSA triple risk model has been suggested for SIDS risk;
· A vulnerable infant
· A critical developmental period in homeostatic control
· Exogenous stressor, such as being placed for sleep in the prone position
The generally recognized risk factors for SIDS as reported in research studies are;
Maternal smoking and smoke exposureMaternal smoking during pregnancy and postnatal exposure to tobacco has emerged as separate risk factor for SIDS. Prenatal smoke exposure causes decreased lung volume and compliance, decreased heart rate variability to stress; nicotine has neuroteratogenic effects resulting in decreased arousal to hypoxia and other stimuli.
Sleep practice and environmentThe side sleep position has increased the risk to SIDS. Side sleep position is unstable and infants may roll to prone increasing the risk of SIDS. Soft bedding and soft surfaces including pillows, quilts, comforters, sheepskin and porous mattresses are all important risk factors. Warmer room temperature and multiple layers of clothing or blankets on the infant also act as a risk factor. Bed sharing with smoking mothers or after consuming alcohol may prove hazardous for the baby.
Infant medical conditionPremature infants or those with low birth weight are at an increased risk of SIDS. Apnoea, upper respiratory tract infection are other risk factors for SIDS.
SiblingsSiblings of SIDS victims are at an increased risk. This may be due to genetic or metabolic disorders.
Prevention of SIDSThe risk to SIDS may be reduced to cut down the deaths of the infants. American Academy of Pediatrics has recommended some suggestions for reducing the risk factors for SIDS.
· Back to sleep, infants should be kept in supine position. Side sleeping is not considered safe.
· Use a firm sleep surface.
· Do not use soft toys or loose objects for infants.
· DO not smoke during pregnancy and after delivery.
· Co sleeping is not recommended. A separate but proximate sleeping environment such as a cot or bassinet close to parent’s bed is preferred.
· Breastfeeding is considered protective for SIDS risk.
· Do not overheat
· Offer a pacifier to the baby at nap time and bed time. Do not reinsert it once the baby goes to sleep.
· Avoid development of positional plagiocephaly, encourage “tummy time” when the infant is awake and playful.
· Do not excessively use car seats or bouncers.
Despite a definite reduction in the cases of SIDS, there still needs a lot to be done in the field. A definitive search strategy is required to look into the causes, pathophysiology of SIDS and suggest effective interventions to avoid the risk of SIDS.
ReferencesChristodoulou, J. (2013, February). Advances in the Genetic Investigation of Sids. Pathology, 45.
Milner, A. (1989, March 18). Sudden Infant Death Syndrome Recent focus on the respiratory system. British Medical Journal, 298, 689-690.
Moon, R. Y., Horne, R. H., & Hauck, F. R. (2007, November 3). Sudden Infant Death Syndrome. The Lancet, 370, 1578-1587.