Aims-To examine the relation between birth weight and cognitive function at
age 11 years, and to examine whether this relation is independent of socia
Methods-Retrospective cohort study based on birth records from 1921 and cog
nitive function measured while at school at age It in 1932. Subjects were 9
85 live singletons born in the Edinburgh Royal Maternity and Simpson Memori
al Hospital in 1921. Moray House Test scores from the Scottish Mental Surve
y 1932 were traced on 449 of these children.
Results-Mean score on Moray House Test increased from 30.6 at a birth weigh
t of < 2500 g to 44.7 at 4001-4500 g, after correcting for gestational age,
maternal age, parity, social class, and legitimacy of birth. Multiple regr
ession showed that 15.6% of the variance in Moray House Test score is contr
ibuted by a combination of social class (6.6%), birth weight (3.8%), child'
s exact age (2.4%), maternal parity (2.0%), and illegitimacy (1.5%). Struct
ural equation modelling confirmed the independent contribution from each of
these variables in predicting cognitive ability. A model in which birth we
ight acted as a mediator of social class had poor fit statistics.
Conclusion-In this 1921 birth cohort, social class and birth weight have in
dependent effects on cognitive function at age 11. Future research will rel
ate these childhood data to health and cognition in old age.