Long term effect of breast feeding: cognitive function in the Caerphilly cohort.

STUDY OBJECTIVE There is evidence suggesting that artificial feeding is associated with a reduction in cognitive function in infants and children, in contrast with breast feeding, but the available evidence suffers from confounding by social and educational factors. An opportunity arose in the Caerphilly cohort study to examine relations between cognitive function in older men and their feeding as infants, when breast feeding was usual. DESIGN A prospective cohort study. SETTING Caerphilly, South Wales, UK, was a deprived coal mining community when the men had been born in 1920-35. Most had been breast fed as infants. PARTICIPANTS 779 men aged 60-74 years when tested. The men had earlier been asked to obtain from their mothers their birth weight, and how they had been fed as infants. RESULTS Complete data were obtained for 779 men. In those whose birth weight had been at or above the median, the adjusted mean cognitive function was only slightly and non-significantly lower in those who had been artificially fed. In the men whose birth weight had been below the median, having been artificially fed was associated with significantly lower results in both a test of reasoning (the AH4) and word power (the national adult reading test (NART)). Two standard deviations below the median birth weight, artificial feeding was associated with a reduction of six points (70% of a SD) on word power (the NART). CONCLUSIONS In men whose birth weight had been low, having been artificially fed is associated with poorer cognitive function in late adult life.