Secular trends in postnatal growth in S. Paulo city, Brazil (1974-1996)

Abstract

OBJECTIVE: Data from three household surveys undertaken in the city of S. Paulo, Brazil, from mid-80s to mid-90s allow to characterize and analyse secular trends in infant and child linear growth. METHODS: In the three surveys, random population samples aged from zero to 59 months (1,008 children in the period of 1974-75; 1,016 in 1984-85 and 1,280 in 1995-96) were studied. Recumbent length was obtained from children up to 24 months of age and then stature was recorded. The international growth standard was used to evaluate the child's height according to age and sex. For the study of the social distribution of growth status, tertiles of the per capita family income was taken into account in each survey. For the study of the determinants of secular trends, hierarchical causal models, multivariate regression analyses and calculations analogous to the ones used to assess population attributable risks were applied. RESULTS/CONCLUSIONS: In the period of 22 years covered by the three surveys, the secular trend of child growth in S. Paulo City showed a positive, continuous and apparently uniform curve. It was equivalent to a total average gain of 0.650 z scores of the international growth reference, or near 2.3 cm at the age of 30 months. The higher gain was observed among the third poorest fraction of the population -- 3.3 cm ;¾; and the lower gain -- 1.7 cm ;¾; among the third richest. Positive changes in distal determinants (family income and maternal schooling) and intermediate determinants (housing, sanitation, access to heath services and reproductive past history) of child growth explained substantially part of the improvements seen from the mid-80s to mid-90s.