Objective: To measure the association between daytime bottle-feeding and iron depletion in young children.
Design: Cross-sectional design with concurrent measurement of exposure and outcome. The exposure was the current container (bottle or cup) used for daytime milk consumption. Child, maternal, and dietary variables were collected.
Setting: Community-based pediatric practice serving a diverse population in an urban Canadian city.
Participants: One hundred fifty healthy children, aged 12 to 38 months, attending a well-child care visit.
Main outcome measure: Iron depletion (serum ferritin level, <10 microg/L]).
Results: Of the 150 children, 82 (55%) were bottle-fed and 68 (45%) were cup fed. Iron depletion occurred in 29 (37%) of 78 bottle-fed and in 12 (18%) of 67 cup-fed children. The crude relative risk for iron depletion was 1.81 (95% confidence interval, 1.09-3.01). In the final logistic regression model, a significant association between bottle use and iron depletion was identified, beginning after the age of 16 months. At 18 months, the relative risk, adjusted for several child, maternal, and dietary variables, for the association between bottle use and iron depletion was 1.31 (95% confidence interval,1.24-1.47); at 24 months, the adjusted relative risk was 2.50 (95% confidence interval, 2.46-2.53). Milk consumption of more than 16 oz/d occurred in 55 (67%) of the 82 bottle-fed and in 22 (32%) of the 68 cup-fed children (P<.001).
Conclusions: In the second and third years of life, there is an almost 2-fold association between iron depletion and daytime bottle-feeding compared with cup feeding. The child's age may be a modifier, and milk volume consumed may be a mediator, of this association. Duration of bottle use is a potentially modifiable practice.