The San Diego SIDS definition-20 Years on.

AIM: As it is now 20 years since the San Diego definition of sudden infant death syndrome (SIDS) was proposed, it is timely to examine the impact of this consensus statement.

RESULTS: Concerns at the time were expressed that 'death scene' had been replaced by circumstances of death and so it may have been more useful to have a more inclusive statement of 'death scene, including circumstances of death'. The category of unclassified sudden infant deaths (USID) that was proposed has not been widely adopted. More disturbing, however, is the increasing failure to use either the San Diego or earlier definitions in published research, with recent studies showing that almost two-thirds of peer-reviewed SIDS publications (2019-2021) did not quote or reference internationally accepted definitions. This is a decrease of 33% from the 68% of papers that correctly used SIDS definitions in 2011. The definition is therefore not being uniformly applied and in addition, diagnostic shift is occurring, with more pathologists favouring 'undetermined' over a designation of SIDS.

CONCLUSIONS: Given these developments, how can we correctly interpret conclusions relating to SIDS research, and can we accurately monitor trends in SIDS mortality? The authors would suggest that unfortunately, at present we cannot with any precision.