Long list of known risk factors, even though mechanism not clearly understood!

Age is probably the main risk factor – mostly 5-10 weeks of age. Very few in later infancy (although sudden death is described in all ages cf SUDEP).

From Scottish study –

So preterm, low birth weight boys with socially deprived unmarried mothers who smoke are at highest risk. But many of these factors compound and confound – 78% have at least 2 risk factors, only 0.8% have no risk factors. If you exclude “non-modifiable risk factors” (social deprivation, etc), only 5.3% have no risk factors.

Prone sleeping is no longer a major factor since it has been discouraged for years. Might be protective for preterms, where found to promote cortical arousal (CA) responses (protective in term infants). Horne 2013

36% of excess infant mortality in US South due to SUDI (90% of excess mortality in Kentucky!  59% due to non-hispanic black population).

Main risk factor now is co-sleeping, esp on sofa, although this is commonly associated with alcohol/drug use. Blair & Sidebotham BMJ 2009

Note used mattress is risk factor in Scotland – never replicated elsewhere.

Dummies are protective, even though they fall out – part of some national safe sleep recommendations but not in UK (perhaps because mechanism unclear?).

Parental mental health associated – if both have a mental health disorder, OR for SIDS =6, more if substance abuse disorder – but smoking/social deprivation explains 50% of this risk.

4% of unselected cases had long QT mutations [NZ] – increased to 16% when cases guided by cardiac genetics.  But poor uptake of screening!

A previous maltreatment report emerged as a significant predictor of SIDS and other SUID. After adjusting for baseline risk factors, the rate of SIDS was more than 3 times as great among infants reported for possible maltreatment (hazard ratio: 3.22; 95% CI: 2.66, 3.89).  [US, PMID 24139442]