Secular trends in child diarrhea in S. Paulo city, Brazil (1984-1996)

Objective Data from two consecutive household surveys undertaken in mid-80s and mid-90s allow to characterize and analyse secular trends in infant and child diarrhea in the city of S. Paulo, Brazil. Methods The two surveys included random population samples aged from zero to 59 months of age (1,016 in the period of 1984-85 and 1,280 in 1995-96). bt both surveys the instant prevalence of diarrhea (proportion of examined individuals reporting three or more episodes of liquid stools in 24 hours) and the annual incidence of hospitalizations due to the disease were calculated These two indicators were estimated from household interviews conducted by pediatricians with the children's mothers. In both surveys the interviews were distributed throughout a period of almost 12 months to assure a uniform coverage of the various areas of the city during the four seasons. For each survey the study of the social distribution of the disease took into account tertiles of the per capita family income. 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 risk were applied. Results/Conclusions In the time span from the first to the second survey there was substantial reduction in both the prevalence of diarrhea (from 1.70% to 0.90%) and the hospitalizations due to the disease (from 2.21 to 0.79 hospitalizations per 100 children-year). A more significant reduction was observed among the third poorest families, narrowing the social gradient relative to the disease. An increase in family income and improvement in water supply could substantially explain part of the decline in the disease and for children under two years of age, a discrete increase in breast-feeding may have also played a positive role.