Sample sizes and IgE by population and age category.

<p>Geometric mean values are in IU/ml. Values in parenthesis are plus or minus two standard deviations for log transformed values: e^µ±2*σ, where µ is the mean of ln(IgE) and σ is the standard deviation of ln(IgE).</p

Association between model parameters and population geometric mean IgE levels.

<p>The upper panel shows fits between age parameters and mean log IgE by population. The lower shows fits between slope parameters and geometric mean IgE by population. Note that the fit for B1 is linear with regard to log IgE, but is shown on the lower graph due to the parameter scale. Correlation coefficients for all parameters are given in the text.</p

Distribution and geometric mean value of IgE antibody levels in three populations.

<p>Density plots were generated with a Gaussian smooth with bandwidth 0.5.</p

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.</p

Non-linear model parameters by population.

<p>Non-linear model parameters by population.</p

Four models comparing age profile parameters among NHANES, Shuar, and Tsimane.

<p>All models are non-linear regression models of the form given in the <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001218#s2" target="_blank">Methods</a> section of this paper. In Model 1 all parameters were entered as functions of population IgE level. For Models 2 and 3 age parameters were instead entered with population identity interaction terms. In Model 3 α₁ and α₃ were entered as functions of α₂. Two-sided t-test significant levels:</p><p>^tp≤0.10.</p><p>*p≤0.05.</p><p>**p≤0.01.</p><p>***p≤0.001.</p

Tsimane helminth prevalences by age group.

<p>Tsimane helminth prevalences by age group.</p

Odds-ratios for Tsimane helminth infection by age relative to the Tsimane population as a whole.

<p>Odds-ratios were estimated with generalized additive models with a binomial logit link function. Shading shows the 95% confidence interval for the odds-ratio. All age functions were significant at p<0.001, except the age function for <i>T. trichiura</i>, which was non-significant.</p