Models for IgE by age in Tsimane, Shuar, and NHANES.

<p>A) Generalized additive models for Tsimane (top, blue), Shuar (middle, green), and NHANES (bottom, yellow). Points show the mean lnIgE value for males (triangles) and females (circles) between knots specified in the initial model basis (vertical lines), while lines indicate the thin plate regression spline for each sex. For all three populations males have the higher fit line. Numbers indicate the estimated ages at which the initial peak in IgE occurs. Shading indicates local 95% confidence intervals for the spline, with dark areas indicating overlap between male and female confidence intervals and light areas indicating no overlap. B) Ordinal step models and non-linear regression models. Ordinal model parameters were entered in stepwise fashion according to AIC minimization, resulting in the final models. Numbers indicate a significant transition at greater than the age given, symbols the significance of the parameter in the model: ^t p≤0.10, * p≤0.05, ** p≤0.01, *** p≤0.001. Dashed lines indicate the model fits for non-linear models, including the population specific models in <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001218#pntd-0001218-t003" target="_blank">Table 3</a> (red), and the interaction models in <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001218#pntd-0001218-t004" target="_blank">Table 4</a> (Model 1 in green, Model 2 in brown, and Model 3 in blue). For simplicity only the models for females are shown.