Breast-feeding and Mental and Motor Development at 5½ Years

Clark, Katy M.; Castillo, Marcela; Calatroni, Agustin; Walter, Tomas; Cayazzo, Marisol; Pino, Paulina; Lozoff, Betsy

doi:10.1016/j.ambp.2005.11.003

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Volume 6, Issue 2 , Pages 65-71, 1 March 2006

Breast-feeding and Mental and Motor Development at 5½ Years

Katy M. Clark, MA
- Center for Human Growth and Development, University of Michigan, Ann Arbor, Mich
Marcela Castillo, PhD
- Psychology Unit, Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile
Agustin Calatroni, MS
- Rho, Inc., Chapel Hill, North Carolina
Tomas Walter, MD
- Hematology Unit, Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile
Marisol Cayazzo, RN
- Psychology Unit, Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile
Paulina Pino, PhD
- Department of Environmental and Occupational Health, School of Public Health, Faculty of Medicine, University of Chile, Santiago, Chile
Betsy Lozoff, MD
- Center for Human Growth and Development and Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor, Mich
- Address correspondence to Betsy Lozoff, MD, Center for Human Growth and Development, 300 N Ingalls, University of Michigan, Ann Arbor, MI 48109-0406

Received 23 August 2005; accepted 22 November 2005.

Objective

Breast-feeding is associated with better child development outcomes, but uncertainty remains primarily due to the close relationship between breast-feeding and socioeconomic status. This study assesses the issue in a low socioeconomic status sample where breast-feeding was close to universal.

Methods

Seven hundred eighty-four Chilean children were followed longitudinally from infancy. All but four were initially breastfed, 40% nursed beyond 12 months, and infant growth was normal. Child development was assessed at 5½ years by a cognitive, language, and motor test battery. The duration of breast-feeding as the sole milk source was analyzed as a continuous variable, adjusting for a comprehensive set of background factors.

Results

The relationship between breast-feeding and most 5½-year developmental outcomes was nonlinear, with poorer outcome for periods of breast-feeding as the sole milk source for <2 months or >8 months—statistically significant for language, motor, and one comprehensive cognitive test, with a suggestive trend for IQ.

Conclusions

The observed nonlinear relationships showed that breast-feeding as the sole milk source for <2 months or >8 months, compared with 2–8 months, was associated with poorer development in this sample. The latter finding requires replication in other samples where long breast-feeding is common and socioeconomic status is relatively homogeneous.

Key words: breast-feeding , mental development , motor development