Growth references for Tsimane forager-horticulturalists of the Bolivian Amazon

Abstract

Objectives: Growth standards and references currently used to assess population and individual health are derived primarily from urban populations, including few individuals from indigenous or subsistence groups. Given environmental and genetic differences, growth may vary in these populations. Thus, there is a need to assess whether international standards are appropriate for all populations, and to produce population specific references if growth differs. Here we present and assess growth references for the Tsimane, an indigenous population of Bolivian forager-horticulturalists.

Methods: Mixed cross-sectional/longitudinal anthropometrics (9,614 individuals; 30,118 observations; ages 0-29 years) were used to generate centile curves and Lambda-Mu-Sigma (LMS) tables for height-for-age, weight-for-age, body mass index (BMI)-for-age, and weight-for-height (WFH) using Generalized Additive Models for Location Shape and Scale (GAMLSS). Velocity curves were generated using SuperImposition by Translation and Rotation (SITAR). Tsimane ≤5 years were compared to World Health Organization (WHO) standards while those >5 years were compared to WHO school age references. All ages were compared to published references for Shuar forager-horticulturalists of the Ecuadorian Amazon.

Results: Tsimane growth differs from WHO values in height and weight, but is similar for BMI and WFH. Tsimane growth is characterized by slow height velocity in childhood and early adolescent peak height velocity at 11.3 and 13.2 years for girls and boys. Tsimane growth patterns are similar to Shuar, suggesting shared features of growth among indigenous South Americans.

Conclusions: International references for BMI-for-age and WFH are likely appropriate for Tsimane, but differences in height-for-age and weight-for-age suggest Tsimane specific references may be useful for these measures.

Keywords: Amazonians; BMI; GAMLSS; Tsimane; growth; growth velocity; height; indigenous South Americans; weight.

Figure 1

Centile curves for Tsimane height, weight, and BMI from age 0 to 25 years. Solid black lines = 50th centile; Dashed slate blue lines = 25th and 75th centiles; Dotted brown lines = 5th and 95th centiles. Complete centile values and accompanying LMS parameters are provided in online Supplemental Files S4–S6 and S8–S13.

Figure 2

Centile curves for Tsimane weight-for-height from age 0 to 25 years. Solid black lines = 50th centile; Dashed slate blue lines = 25th and 75th centiles; Dotted brown lines = 5th and 95th centiles. Complete centile values and accompanying LMS parameters are provided in online Supplemental Files S7 and S14–S15.

Figure 3

Tsimane LMS parameters in the first two years of life, relative to WHO standards. Lines indicate parameter values for Tsimane (solid, brown) and WHO (dashed, slate blue). Shading on median graphs indicates the range between the 5^th and 95^th percentiles. µ = median parameter, i.e. the 50^th percentile. σ = sigma parameter, indicative of variation in the distribution. λ = lambda parameter, indicative of skew in the distribution; values >1 indicate negative skew and < 1 indicate positive skew.

Figure 4

Tsimane LMS parameters from 2 to 25 years of age, relative to WHO standards (under age 5) and WHO references (over age 5). CDC references are used for weight-for-age over age 10, since the WHO does not provide weight-for-height references for these ages. Lines indicate parameter values for Tsimane (solid, brown), WHO (dashed, slate blue), and CDC (solid, slate blue),. Shading on median graphs indicates the range between the 5^th and 95^th percentiles. µ = median parameter, i.e. the 50^th percentile. σ = sigma parameter, indicative of variation in the distribution. λ = lambda parameter, indicative of skew in the distribution; values >1 indicate negative skew and < 1 indicate positive skew.

Figure 5

Tsimane LMS parameters for weight-for-height relative to WHO standards. Lines indicate parameter values for Tsimane (solid, brown) and WHO (dashed, slate blue). Shading on median graphs indicates the range between the 5^th and 95^th percentiles. µ = median parameter, i.e. the 50^th percentile. σ = sigma parameter, indicative of variation in the distribution. λ = lambda parameter, indicative of skew in the distribution; values >1 indicate negative skew and < 1 indicate positive skew.

Figure 6

Tsimane velocity curves for the first 2.5 years of life. Tsimane curves derived from cross-sectional GAMLSS (brown) and SITAR (scatter points, slate blue line) analyses are shown, relative to WHO curves derived from the median of the cross-sectional (dashed black line) or longitudinal velocity standards (solid black line). Shading shows the 5^th to 95^th percentiles for the WHO growth velocity standards.

Figure 7

Tsimane velocity curves 2 to 25 years of age. Tsimane curves derived from cross-sectional GAMLSS (orange) and SITAR (scatter points, olive line) analyses are shown, relative to WHO (solid black line) standards (under age 5) and references (over age 5) and CDC references (dashed black line).

Figure 8

Comparison of Tsimane and Shuar (Urlacher et al., 2016) growth references. Left, overlay of Shuar (black solid line, grey shading), Tsimane (dotted black line, tan shading), and WHO standards/references (dashed blue line, blue shading) or CDC references for weight over age 10 (solid line, blue shading). Middle, comparison of Shuar (solid black), Tsimane (solid tan), and WHO (dashed blue) or CDC (solid blue, weight only) pseudo-velocity curves. Right, comparison of Z-scores obtained for Tsimane using WHO standards/references (TvW), Tsimane using Shuar references (TvS) and Shuar using Tsimane references (SvT) at the values corresponding to −2 (blue), 0 (orange), or +2 (yellow) Z-scores on the original reference. Bars within each grouping represent age groups of 0–2, 2–5, 5–10, 10–15, and 15–20 years in increasing order. Note TvW for weight over age 10 also uses CDC references instead of WHO standards/references.

Figure 9

WHO (slate blue) or Shuar (tan) centile or z-score values for equivalent Tsimane values for height or weight. Lines, from thinnest to thickest, represent values at 1, 2, 5, 10, and 20 years of age, respectively. For weight over age 10, CDC references are used instead of WHO.

Figure 10

WHO (slate blue) or Shuar (tan) centile or z-score values for equivalent Tsimane values for height or weight. For BMI, lines, from thinnest to thickest, represent values at 1, 2, 5, 10, and 20 years of age, respectively. For WFH, lines represent 60, 80, 100, and 120 cm, respectively.