History and exam
Key diagnostic factors
common
presence of risk factors
Major risk factors include prone, side, or inclined position at last sleep, bed-sharing, soft sleeping surface/environment, maternal cigarette smoking, increasing number of smokers in house, smoking in same room as child, premature birth, formula feeding, non-use of pacifier, and maternal alcohol or drug use.
No factor appears to be sufficient, in itself, to initiate a SIDS event. Risk factors should be placed in the Triple-Risk hypothesis model and the aggregate of co-existing factors used to evaluate the risk of a SIDS event in any given patient.
A recent survey of 244 SIDS cases found that 78% of cases had 2 or more concurrent risk factors (modifiable or non-modifiable), while almost 35% had 4 or more.[119]
Other diagnostic factors
common
absence of metabolic disease
Family history of syndromes or metabolic disorders, for example errors of fatty acid metabolism, and features of dysmorphia.
absence of irritability, lethargy
Presence may indicate infection, metabolic disease, or dysrhythmia.
absence of fever, cough, or nasal congestion
Presence may indicate infection such as pertussis or respiratory syncytial virus.
absence of trauma
Presence may indicate non-accidental injury. Injury can be acute or old.
Exact mechanism of injury should be established.
Risk factors
strong
side, prone, or inclined position at last sleep
Sleeping in the side or prone position significantly increases the risk of SIDS compared with sleeping in the supine position. The risks of sleeping in the prone or side position are similar (odds ratio: 2.6 and 2.0, respectively).[47] Indeed, the population-attributable risk for side position is greater than that for prone position.[48][49] The side position is unstable, and many infants who start sleep in the side position may roll into the prone position.[49][50]
Inclined sleep products in which the infant is at a >10 degree incline are not safe for infant sleep. The inclined baby is more likely to roll to the side or prone. When this occurs, the baby is at higher risk of muscle fatigue and suffocation.[51]
In a nationally representative US study, fewer than half the mothers surveyed always placed their infants to sleep supine.[52]
The association of SIDS and prone sleep position is particularly high in infants born preterm.[53] Preterm infants should be placed in the supine position for sleep as early as possible.
There is no evidence that the supine sleep position increases the risk of aspiration. Infants with gastro-oesophageal reflux should be placed supine for sleep unless there is associated absence of protective airway reflexes (i.e., the risk of death from gastro-oesophageal reflux is greater than the risk of SIDS).[54]
bed-sharing/co-sleeping
Bed-sharing remains a controversial issue. Bed-sharing facilitates breastfeeding,[55] and many parents believe that it facilitates parent-infant bonding and monitoring of the infant.[56] However, bed-sharing, as it is frequently practised in Western countries, can increase the risk of SIDS and accidental deaths (e.g., suffocation, entrapment) in infants.[57][58][59][60][61][62][63]
Bed-sharing with one or both parents who smoke increases the risk of SIDS to a greater extent (odds ratio [OR}: 2.3 to 17.7) than sharing with non-smoking parents.[49][64][65][66][67][68] Bed-sharing on a surface with soft bedding accessories, such as pillows and blankets, increases the risk of SIDS (OR: 2.8 to 4.1),[69][70] as does sharing with an adult who has consumed alcohol (OR: 1.66)[71][72] or with someone who is not a parent (OR: 5.4).[69]
Younger age (<11 weeks) increases the risk of SIDS during bed-sharing (OR: 4.7 to 10.0), even if the parents are non-smokers.[64][66][68][72][73][74]
Sleeping with an infant on an extremely soft surface, such as a couch, sofa, armchair, or waterbed increases the risk of SIDS (OR: 5.1 to 66.9) when compared with crib-sleeping.[49][64][66][69][73]
Room-sharing without bed-sharing (i.e., having the infant sleep in a crib or bassinet near the parent’s bed) decreases the risk of SIDS, suffocation, strangulation, and entrapment and is safer than bed sharing or solitary sleeping (when the infant is in a separate room).[48][64][66][72]
soft sleeping surface/environment
An independent risk factor for SIDS (odds ratio 5).[59][69]
The combination of a soft sleeping surface and prone sleeping position increases the risk as much as 21-fold.[69]
Pillows and bedding that cover the head during sleep are also associated with increased risk. It is thought that head coverage during sleep is linked to the development of an over-heated sleeping environment.
maternal cigarette smoking
Maternal smoking during pregnancy is associated with a two- to fourfold increase in risk of SIDS.[75][76][77] Even smoking 1 cigarette daily during pregnancy increases the risk twofold; there is a linear association between cigarettes smoked and SIDS risk; the more cigarettes smoked, the greater the risk.[78] Almost 25% of all SIDS deaths seem to be attributable to antenatal smoking.[78][79]
Postnatal maternal smoking is also associated with an increased risk; however, the exact level of risk is difficult to ascertain, as mothers who smoke postnatally are also likely to smoke antenatally.
increasing number of smokers in house
smoking in same room as child
formula feeding
Consistently associated with increased risk of SIDS.
A case-control study found that exclusive breastfeeding at 1 month of age was associated with a 50% reduction in SIDS, and that partial or exclusive breastfeeding was protective, even after adjusting for confounding factors.[82]
A meta-analysis found that, when adjusted for confounding factors, any breastfeeding decreased the risk of SIDS (odds ratio 0.55 compared to formula-fed infants) and that exclusive breastfeeding was even more protective (odds ratio 0.27 for any duration of exclusive breastfeeding).[83] A minimum of 2 months’ breastfeeding (either partial or exclusive) is necessary to confer a protective effect of breastfeeding.
non-use of a dummy
Multiple studies, including two meta-analyses, have demonstrated a protective effect of dummy use.[84][85] While the meta-analyses have demonstrated a 50% to 60% decrease in SIDS risk, other studies have shown as much as a 90% decrease in risk.[86][87]
Introduction of a dummy in breastfed infants after 2-3 weeks of life does not impact on breastfeeding duration.[88] A dummy can be introduced to breastfed infants after breastfeeding has been established.[3]
premature birth
Preterm infants are at an increased risk for SIDS, the risk being inversely proportional to gestational age and birth weight.
Infants born weighing <1500 g have a fourfold increased risk compared with those born weighing >2500 g.[89]
A high percentage of reported apparent life-threatening events (ALTEs) occur in infants born at <38 weeks' gestation.[90] However, a history of ALTEs is not independently associated with an increased risk of SIDS.
weak
maternal substance use/abuse
It is difficult to determine the independent contribution of alcohol consumption, cannabis, opioid, or illicit drug use during pregnancy to an increased risk of SIDS, because it is often difficult to separate the risk of these separate behaviours from smoking. However, increased risks have been described in some populations following either binge or early trimester alcohol consumption.[91][92]
Cannabis use during pregnancy may be a weak independent risk factor for SIDS.[93] However, other forms of perinatal substance use (opioids, cocaine, phencyclidine, and amfetamines) increase the risk of SIDS up to fourfold.[94]
There is particular concern with parents who are smokers, or who have consumed alcohol or arousal-altering drugs bed-sharing with their infants, as the risk of SIDS is particularly high in these cases.[49][66][72][95]
single parent
Has consistently been associated with an increased incidence of SIDS. However, the impact is difficult to determine, as the associations between this and other socio-demographic factors and practices associated with SIDS are likely to be complex.[96]
lower maternal age
Has consistently been associated with an increased incidence of SIDS. However, the impact is difficult to determine, as the associations between this and other socio-demographic factors and practices associated with SIDS are likely to be complex.[96]
low level of antenatal care
Associated with an increased incidence of SIDS. However, the impact is difficult to determine, as the associations between this and other socio-demographic factors and practices associated with SIDS are likely to be complex.[96]
low level of maternal education
low socio-economic status
lack of immunisation
Because of the temporal association between age at initial immunisations and the age of greatest SIDS risk, claims that immunisations have a causative role in SIDS have been made. Subsequent case-control studies have consistently shown immunisations not to be a risk factor for SIDS, and a meta-analysis showed a roughly 50% reduction in SIDS incidence in infants who were immunised.[97]
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