Research ArticleANTHROPOLOGY

Rapidly declining body temperature in a tropical human population

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Science Advances  28 Oct 2020:
Vol. 6, no. 44, eabc6599
DOI: 10.1126/sciadv.abc6599
  • Fig. 1 BT of adults (>15 years) by age, sex, and time period.

    Shown are unadjusted values smoothed with generalized additive models using a cubic spline. Time periods are divided as October 2002–June 2006 (n = 1269 observations, oral temperature), July 2006–July 2012 (n = 10,496, tympanic), and August 2013–December 2018 (n = 6193, tympanic).

  • Fig. 2 Predicted BT by study date.

    Shown for women (A) and men (B). Shaded region outlined by dashed line denotes 95% CI. Based on model 3 from Table 1. All covariates are set to population mean.

  • Fig. 3 Secular trends in biomarkers and disease ecology for Tsimane adults (>15 years).

    Blue and red represent males and females, respectively, in (A) to (E). (A, D, and E) Predicted means (±95% CI) by sex across the study period from models of ESR (log-transformed), leukocyte count (WBC) (log-transformed), and eosinophils (% of WBC). (B) Physical activity, as average steps per day, from triaxial accelerometry (see Materials and Methods). (C) is RMR (kcal/day) based on indirect calorimetry (using Cosmed Fitmate MED). (F) Modeled prevalence of four helminth species, based on direct microscopy from fecal smears. (G and H) Per-year means of age-standardized prevalence by illness categories based on clinical ICD-10 diagnoses, separated by whether or not the category was a significant predictor of BT. All models adjust for age, sex, and season (shown “wet”) and include study community and individual ID random effects. Models in (A), (D), and (E) also adjust for age2, sex*age, and sex*age2. Model in (B) is a Bayesian generalized additive multilevel model using a thin-plate smoothing spline for date interacted with sex, adjusting for sex, age, age2, sex*age, season, and a community random effect. Model in (C) also adjusts for weight, height, ambient temperature, time of day of measurement, and time since last meal. Models in (F) are Bayesian generalized additive multilevel models fit separately by helminth species using a thin-plate smoothing spline for date, adjusting for age, season, and community and individual ID random effects. Model results for (A), (C), (D), and (E) are shown in table S7, and model results for (B) and (F) are shown in table S8.

  • Table 1 Mixed-effects models of BT.

    All models include random intercepts for individual ID, community ID, and physician ID.

    Dependent variable: BT
    Model 1Model 2Model 3
    PredictorsBaseBase + weatherBase + weather + diseases
    Height (cm)−0.001−0.002−0.001
    (−0.003, 0.0004)(−0.003, 0.0001)(−0.003, 0.0001)
    Weight (kg)0.0010.001*0.001**
    (−0.0001, 0.002)(0.0003, 0.002)(0.0005, 0.002)
    Age (years)−0.003***−0.003***−0.003***
    (−0.004, −0.003)(−0.004, −0.002)(−0.003, −0.002)
    Sex (reference = female)0.171*0.1390.142
    (0.003, 0.339)(−0.025, 0.303)(−0.022, 0.305)
    Male: age−0.001−0.001−0.001
    (−0.002, 0.0002)(−0.002, 0.0002)(−0.001, 0.0002)
    Date (years)−0.055***−0.054***−0.054***
    (−0.061, −0.049)(−0.060, −0.049)(−0.060, −0.049)
    Male: date−0.005**−0.005*−0.005*
    (−0.010, −0.001)(−0.009, −0.001)(−0.009, −0.001)
    Method (reference = “ear”)−0.050*−0.040*−0.046*
    (−0.090, −0.010)(−0.080, −0.001)(−0.085, −0.007)
    Season (reference = “dry”)0.041***0.040***
    (0.024, 0.058)(0.023, 0.057)
    Average ambient temperature0.029***0.029***
    (°C)(0.027, 0.031)(0.027, 0.031)
    Infectious/parasitic diseases−0.017
    (Yes/no)(−0.034, 0.001)
    Blood diseases−0.003
    (Yes/no)(−0.031, 0.025)
    Nervous system/sensory−0.016
    (Yes/no)(−0.035, 0.003)
    Respiratory system0.075***
    (Yes/no)(0.058, 0.092)
    Digestive system−0.007
    (Yes/no)(−0.021, 0.008)
    Genitourinary system0.025**
    (Yes/no)(0.008, 0.043)
    Skin/subcutaneous0.038*
    (Yes/no)(0.001, 0.075)
    Musculoskeletal system−0.012
    (Yes/no)(−0.026, 0.003)
    Constant39.412***38.574***38.533***
    (39.069, 39.754)(38.235, 38.913)(38.192, 38.874)
    Observations16,83016,83016,830
    R2 (marginal/conditional)0.13/0.410.16/0.450.17/0.45
    Log likelihood−9891.67−9444.39−9421.74
    Akaike information criterion19,809.3518,918.7718,889.48

    *P < 0.05.

    **P < 0.01.

    ***P < 0.001.

    Supplementary Materials

    • Supplementary Materials

      Rapidly declining body temperature in a tropical human population

      Michael Gurven, Thomas S. Kraft, Sarah Alami, Juan Copajira Adrian, Edhitt Cortez Linares, Daniel Cummings, Daniel Eid Rodriguez, Paul L. Hooper, Adrian V. Jaeggi, Raul Quispe Gutierrez, Ivan Maldonado Suarez, Edmond Seabright, Hillard Kaplan, Jonathan Stieglitz, Benjamin Trumble

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      • Figs. S1 to S6
      • Tables S1 to S12

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