Influence of socioeconomic conditions on growth in infancy: the 1921 Aberdeen birth cohort

Objectives-To identify environmental influences on infant growth using data from a birth cohort established in 1921. Design-A longitudinal cohort study. Setting-Aberdeen 1921-22. Subjects-Five hundred and sixteen individuals (263 boys and 253 girls) born in Aberdeen during 1921. Health visitor assessments ranged from two to 40 (47% received at least 10 visits). No records were available for infants wh o died. Individuals were grouped as those who did not breast feed, those wh o breast fed initially but not at 6 months, and those who were continuing t o breast feed at 6 months. Main outcome measure-Fate of weight gain over th e Ist year of life. A random effects model was used to identify environment al factors and conditions contributing to rate of weight gain in the Ist ye ar of life. Results-Breast feeding rates were about 80% and 50% at 10 days and 6 months , respectively. Breast fed infants were significantly heavier than bottle f ed infants at 28 days but this difference disappeared by 12 months. Signifi cant negative effects on rate of weight gain, independent of initial body w eight, were found for overcrowding in family homes and maternal parity, whe reas social class had no effect. Conclusion-Studies based on historical cohorts that have controlled socioec onomic variables only in terms of social class (derived from parental occup ation) may have been subject to residual confounding. Growth in the Ist yea r of life is likely to reflect a number of environmental influences, some o f which may continue to have effects throughout early life and beyond.