Determinants of mental and motor development at 12 months in a low income population: a cohort study in northeast Brazil

Aim: To identify biological and environmental factors associated with poorer mental and motor development at age 12 mo in urban communities in northeast Brazil. Methods: A cohort of 245 infants born during January-August 1998 in six hospitals in the interior of Pernambuco was followed twice weekly from birth until 12 mo of age. Socio-economic, demographic and environmental data were collected, together with daily information on morbidity and feeding patterns. Gestational age, birth anthropometry and nutritional status at 12 mo were measured. Multiple linear regression analysis was used to identify variables that had independent effects on mental and motor development assessed at 12 mo of age with the Bayley Scales of Infant Development. Results: Environmental factors explained about 21% and 19% of the variance in mental and motor development, respectively. Of these, the most important were poverty-related. Significant biological factors associated with mental development were birthweight and infant sex. For motor development, the biological factors were weight-for-age and haemoglobin concentration. Biological factors explained only 6% and 5% of the variance in mental and motor development, respectively. Conclusion: Of the variables examined, environmental factors had a greater detrimental effect on child development than biological factors in this population. Interventions that enhance social capital and alleviate poverty are advocated.