Tsimane Child and Maternal Anthropometrics

Infant and child height (or length) were measured by trained Tsimane research assistants using a portable Seca infantometer or stadiometer (Hamburg, Germany). For the purposes of analysis, length and height were treated interchangeably. Weight was measured using a Tanita digital scale to the closest tenth of a kilogram. If infants were too small to stand on the scale, their weight was calculated by subtracting the weight of the mother from the combined weight of the mother holding her infant. Maternal height and weight measures were collected using the same instruments as used for the child, either at the same visit, or within 30 days of the child’s visit. Tsimane-specific z-scores for HAZ, child WHZ and maternal BMI-for-age (BMIZ) were calculated using the open-source R package localGrowth (https://github.com/adblackwell/localgrowth), which utilizes growth curves from [39 (link)]. These growth references better describe intra-population comparison by using locally-relevant growth trajectories [39 (link)]. Child WHZ and maternal BMIZ (in models for children under 3 years) were used as markers of energetic status, to model the effects of interactions between child energetic status and immune function on child HAZ. To determine the child’s age, exact birthdates were verified by the mother or pulled from longitudinal THLHP medical records.