The reference cited in the fourth sentence of the “Statistical analyses” section are incorrect. The sentence should read: PRRs were used because the outcome variable had prevalence above 10% (Zocchetti et al., 1997; Traissac et al., 1999; Barros et al., 2003).The correct references are:Zocchetti, C., D. Consonni, and P.A. Bertazzi, Relationship between prevalence rate ratios and odds ratios in cross-sectional studies. Int J Epidemiol, 1997. 26(1): p. 220–3.Traissac, P., Y. Martin-Prevel, F. Delpeuch, and B. Maire, [Logistic regression vs other generalized linear models to estimate prevalence rate ratios]. Rev Epidemiol Sante Publique, 1999. 47(6): p. 593–604.Barros, A.J. and V.N. Hirakata, Alternatives for logistic regression in cross-sectional studies: an empirical comparison of models that directly estimate the prevalence ratio. BMC Med Res Methodol, 2003. 3: p. 21.