Epidemiology of sudden infant deaths in cities of Rio Grande do Sul, Brazil. A comparative study of cases and controls

All post-perinatal infant deaths occurring within a one-year period in 10 cities in the State of Rio Grande do Sul (Brazil), the metropolitan area of Porto Alegre included, were investigated in a case-control study. Seventy-two sudden infant deaths (SID) were identified through a complex monitoring system. These were investigated in detail through medical interviews with the children's parents and through the review of medical records. Such deaths were more common in males, during the first three months of life, and in the winter. The comparison of each case with two neighborhood control infants through multiple conditional logistic regression identified the following risk factors: low socio-economic level (measured by family income and maternal education), low birthweight, presence of other children in the household, low maternal age, maternal smoking, and mixed or artificial feeding. None of the 72 deaths had been certified as such by the physicians who filled in the death certificates, the majority of which referred to 'bronchopneumonia' as the undereying cause.