Introduction: Within New Zealand the SIDS mortality rate is higher in Maori than in non-Maori, predominantly European.
Aims: This paper addresses two questions (1) How should ethnicity be defined, by biological or cultural criteria? (2) Why is the SIDS rate higher in Maori, because of different risk factors or because of a higher prevalence of common risk factors?
Methods: A nationwide case-control study.
Results: The majority of mothers with some Maori blood (as reported on the infants birth registration form) report they are Maori (as recorded in the obstetric records or interview). Risk factors for SIDS are similar in the various ethnic groups in New Zealand.
Conclusions: Using a biological definition underestimates the number of Maori infants compared to the cultural definition. Differences in SIDS mortality appear to be explained by differences in prevalence of known risk factors, the most important of which, prone sleeping position, maternal smoking, lack of breast feeding and bed sharing, are culturally determined rather than biologically.