Objective: To determine whether the risk of the sudden infant death syndrome is increased in bottle fed babies.
Design: Population based case-control study matching for age and time.
Subjects: All babies aged 1 week to 1 year dying of sudden infant death syndrome during November 1987 to April 1989 or February 1990 to June 1991 and two live controls.
Setting: Avon and north Somerset.
Main outcome measures: Breast or bottle feeding, sleeping position, maternal smoking, parental employment, and length of gestation.
Results: Compared with being fully breast fed, the crude odds ratio for sudden infant death in fully bottle fed babies was 3.1 and for mixed breast and bottle fed babies 1.5. These odds ratios fell to 1.8 (95% confidence interval 0.7 to 4.8) and 1.2 (0.5 to 2.7) respectively after maternal smoking, parental employment, preterm gestation, and sleeping position had been adjusted for. Sleeping position partly masked the effect of being bottle fed on sudden infant death as breast fed babies were more likely to have slept prone than bottle fed babies.
Conclusions: Bottle feeding is not a significant independent risk factor for the sudden infant death syndrome. Patterns of maternal smoking, preterm gestation, and parental employment status account for most of the apparent association with bottle feeding.