Impacto do uso da água de cisternas na ocorrência de episódios diarréicos na popula？？o rural do agreste central de Pernambuco, Brasil

objectives: to evaluate the impact of the use of water-tanks on the occurrence of episodes of diarrhea, comparing the number and duration of episodes among the residents of households with and without water-tanks in the same geographical area. methods: a longitudinal prospective study, nested in a cross-section study comparing two groups (households with and without water-tanks), was carried out in 21 municipalities in the central agreste region of the brazilian state of pernambuco, in 2007. data was gathered over 60 days and included 1,765 individuals. descriptive analysis was carried out using mixed hierarchical models, mann-whitney and kaplan-meyer with the level of significance set at 5%. results: among the 949 individuals with water-tanks, there was a reduction in the risk of the occurrence of episodes of diarrhea of 73% compared with the 816 individuals without water-tanks (rr=0.27; p<0.001). the mean number of episodes registered among residents of households without water-tanks was 0.48 (sc=1.17), compared with 0.08 (sc=0.32) among households with water-tanks (z=-10.26; p<0.001). the mean during of episodes was 1.5 times greater in households without water-tanks (χ2=8.99; p=0.003). conclusions: the findings of this study point to the importance of access to drinking water for the reduction of disease. the occurrence of diarrhea and its concomitant severity indicators-number of episodes and duration-were consistently higher among residents of households without water-tanks.