Univariate and multivariable polytomous logistic regressions for factors associated with age of first infection with any STH parasite.

Multivariable analyses included data from 1,381 children for whom we had complete data. Associations between risk factors and age at first infection were compared to children without any infection in the first 3 years of life using univariate and multivariable multinomial logistic regression. STH were detected using all 3 microscopic detection methods. Variables with more than 2 groups in Tables 1 and 2 were redefined as binary. Overcrowding was defined as number of household members per sleeping room using the mean as cut-off. SES (socioeconomic) index shows tertiles of Z scores calculated using principal components analysis. The analysis controlled also for gender of the child, number of stool samples collected and number of anthelmintic treatments received. Maternal infection intensities with A. lumbricoides and T. trichiura were not included. Paternal STH infection was excluded from the multivariate model because of missing data.