DOI: 10.5061/dryad.4j0zpc8js
title: Adolescence is characterized by more sedentary behavior and less physical activity even among highly active forager-farmers

description: Over 80% of adolescents worldwide are insufficiently active, posing
 massive public health and economic challenges. Declining physical activity
 (PA) and sex differences in PA consistently accompany transitions from
 childhood to adulthood in post-industrialized populations and are often
 attributed to psychosocial and environmental factors. An overarching
 evolutionary theoretical framework and data from pre-industrialized
 populations are lacking. This cross-sectional study tests hypotheses from
 life history theory, that adolescent PA is inversely related to age, but
 this association is mediated by Tanner stage, reflecting higher and
 sex-specific energetic demands for growth and reproductive maturation.
 Detailed measures of PA and pubertal maturation are assessed among Tsimane
 forager-farmers (age: 7–22 yrs.; 50% female, n=110). Most Tsimane sampled
 (71%) meet World Health Organization PA guidelines (≥60 minutes/day of
 moderate-to-vigorous PA). Like post-industrialized populations, sex
 differences and inverse age-activity associations were observed. Tanner
 stage significantly mediated age-activity associations. Adolescence
 presents difficulties to PA engagement that warrant further consideration
 in PA intervention approaches to improve public health.
description: Experimental design Data for this study were collected among
 Tsimane children and adolescents from four adjacent villages located along
 the Maniqui River in the summer of 2014 in collaboration with the Tsimane
 Health and Life History Project. To encompass the transition from
 childhood to adulthood, a wide age range of participants (ages 7–22) was
 recruited, in line with a broader conceptualization of adolescence that
 extends the upper limit to align more closely with brain development. The
 average age of menarche in the Tsimane is 13.9 years. Tsimane children and
 younger adolescents play with others in neighboring families, assist in
 caring for younger siblings and food production, and spend limited time in
 formal schooling compared to children in post-industrialized populations.
 Older Tsimane adolescents in this age range are typically married with
 children, and produce food, but typically reside in family clusters and
 are still reliant on their parents and grandparents for additional food
 production and allocare. Participants were recruited during their
 annual medical exam with the THLHP medical team by AC and PH. All
 individuals between the ages of 7–22 who attended their medical exam were
 invited to participate (n=126, 37% of individuals in this age range were
 residents in these communities in 2014). Participation lasted 3–4 days allowing
 inclusion of all eligible participants from each community during the
 medical team visit (1–3 weeks). On Day 1, participants and parents
 provided informed consent/assent, completed a structured interview, and
 had anthropometric and strength measurements taken (detailed below).
 Participants wore ActiGraph wGT3X+ accelerometers on their hip for the
 duration of study participation. On days 2 and 3, participants provided
 first void urine samples to measure urinary hormones (detailed below). On
 days 2, 3, and 4 (where possible) participants completed 24-hour PA recall
 interviews while concurrently examining Actigraph data on a computer
 screen to validate wear-time and aid in recall. Small gifts were provided
 to remunerate participants for each day of study participation including
 pens and notebooks, backpacks, soccer jerseys, sardines, and
 oil. All study methods were
 approved by the Institutional Review Board (IRB) at the University of New
 Mexico (HRRC # 07–157). Informed consent was established at three levels:
 (1) the Tsimane governing council; (2) village leadership; and (3) study
 participants. Informed assent was established with parents/guardians of
 minors. Participant
 Characteristics A total of
 110 Tsimane children and adolescents (mean±SD age = 13.7±3.2 y, 50%
 female) were sampled from four villages (Supplemental Figure 2). Table 1
 summarizes sample characteristics for all variables of interest in the
 full sample, separately by sex, and within-sex by Tanner stage. Males and
 females were similar with respect to mean age, weight, height, DHEA,
 testosterone, and distribution across Tanner
 stages, <em>Χ<sup>2 </sup></em>(4, n=110) =
 1.34,<em> p</em>=0.85. Males have significantly higher grip
 strength, non-significantly (<em>ns)</em> higher mean height
 velocity (4.5 ± 2.2 vs. 3.7 ± 2.9 cm/year, <em>p</em>=0.09);
 while females had significantly higher mean body fat. The highest mean
 height velocity across Tanner stages was the same in males and females
 (6.4 cm/year) and was observed in Tanner 2 females and Tanner 3
 males. Measures
 <em>Age and Anthropometry. </em>Age was obtained from
 census data collected by the Tsimane Health and Life History Project
 (THLHP) over the past 20 years. Height was measured to the nearest mm with
 a portable stadiometer (Seca 213) and weight with a digital scale (Tanita
 BC-1500). Body fat was estimated using the Jackson & Pollack
 3-measurement skinfolds taken in triplicate using FatTrack®II Digital Body
 Fat Calipers (AccuFitness). Grip strength was measured taking the average
 of three measurements using a hydraulic dynamometer (Baseline,
 TN). <em>Free-living PA and sedentary
 time. </em>ActiGraph wGT3X+ accelerometers were used to estimate
 PA/sedentary time and intensity. Actigraphs were initialized with a 30hz
 sampling rate. Participants were fitted with the device on the hip,
 instructed on the proper positioning and to only remove the device when
 submerging themselves in water. Daily 24-hour activity recall interviews
 were completed to assess activity types among participants who lived
 within a reasonable distance from the mobile medical camp and could return
 daily. To aid participants’ recall of the previous day and validate
 Actigraph wear-time in real-time, investigators and participants viewed
 Actigraph data together on a laptop screen while completing the
 interview.  Completed files were downloaded using Actilife software with
 the normal filter into 60-second epochs and converted to CSV tables. Data
 were processed in R (v4.1). Wear-time was additionally assessed using a
 criterion of 60 consecutive minutes of zero-counts with an allowance of
 1–2 minutes of counts to 100. Epochs were delineated into periods of
 sedentary, light and MVPA activity-levels with an algorithm developed in
 Brazilian adolescents using vector magnitude counts. Sixty-second activity
 data were summed into person-day summaries including separating the
 12-hour periods from 7am to 7pm and 7pm to 7am. Person-day summaries were
 averaged into individual daily estimates of activity. Participants were
 included in analysis if there were at least 10 hours of valid wear time
 between 7am and 7pm. Reported daily estimates for light intensity, MVPA,
 and steps/day were based on a 24-hour day from 7am until the following
 morning at 7am; while sedentary activity was based on a 12-hour period
 from 7am-7pm to separate daytime sedentary behavior from sleep. For
 daytime sedentary behavior, person-day level data were included if there
 were at least 9 hours of valid wear time between 7am and 7pm. Of the
 initial 110 enrolled in the accelerometry protocol, four did not meet the
 criteria of at least 1 valid day daytime sedentary behavior and an
 additional two participants did not meet the valid wear-time criteria for
 PA (Figure 4). The remaining participants provided 1.9 days (SD=0.4) of
 data. Previous work indicates that 1-3 days of accelerometer wear-time is
 sufficient to capture reliable estimates of habitual PA. We examined the
 reliability of our estimates using a larger unpublished dataset of
 wrist-worn Actigraph estimates of steps/day for 1986 person-days among
 n=299 Tsimane (age 7–22) with ≥ 4 valid-days of PA data (collected
 2019–2022). The correlation of steps/day estimated using all valid days
 with steps/day estimated with a random selection of only 2 days was strong
 (<em>r</em>=0.76, <em>p</em> &lt; 0.001) with
 good reliability (ICC = .74, p&lt;0.001), suggesting 2 valid days of
 accelerometer data is sufficient to estimate habitual PA.
 Daily 24-hour activity recall interviews were completed among
 n=99 participants, covering an average of 3.8 days (SD=0.06), 15.6 hours
 per day (SD=3.0), and 3601 minutes per participant (SD=962). In total, 62
 activities were recorded with mean=37 activities (SD= 9.1)
 recorded/participant. The 62 activities were coded using previously used
 Troject time allocation codes. Activities were grouped into 9 bins along
 two dimensions: intensity (sedentary, light, moderate to high) and type
 (transportation, habitual/obligatory, and leisure) by AC and HD and
 modified until consensus was reached among all authors who have completed
 fieldwork with the Tsimane (Table S2). Sleep was not included in the
 results and accounted for 43.3% of total recall time. Time periods when
 participants couldn’t recall what they were doing for a given time-period,
 and activities involving medical exams or interaction with anthropologists
 were also excluded, accounting for 8.9% of time captured by the
 interviews. <em>Tanner Stage.</em> Tanner
 staging is considered the gold standard for tracking the development and
 sequence of secondary sex characteristics throughout puberty. It is
 typically evaluated on a scale from 1–5 by a physician through clinical
 examination of secondary sex characteristics such as pubic hair growth and
 breast/genital development. However, it is challenging to perform in field
 settings because of the sensitivity of the assessment and the need for
 privacy – particularly in anthropology field settings where direct
 examinations, interviews, or pictorial representations of breasts and
 genitals are not culturally appropriate. Thus, Tanner stage 1–5 was
 assessed by two authors (AC and PH) independently based on secondary
 sexual characteristics visible through clothing, including breast
 development and underarm hair, as well as menarche, lactation status and
 reproductive history obtained from THLHP medical records. Facial/underarm
 hair, muscular development, jaw shape, and voice change served as
 additional maturation cues in males. Inter-rater reliability was high,
 with discrepancies reflecting only ±1 stage difference that were resolved
 through discussion between researchers. Tanner stage assessments were
 validated with measures of growth and reproductive maturation.
 <em>Urinary Hormone Assays. </em>First morning void
 urine specimens were collected by participants on two consecutive days,
 and frozen in liquid nitrogen within several hours of specimen collection.
 They were stored for up to one month in liquid nitrogen, before being
 transferred on dry ice to the US where they were stored at -80C for two
 years before analyses. After arrival, specimens were thawed, specific
 gravity was measured with a refractometer (Atago, Inc), and urine
 specimens were analyzed in duplicate via enzyme immunoassay for DHEA (Enzo
 Life Sciences, ADI-901-093) and testosterone (R156/7). All specimens were
 run on the first freeze thaw, and results were specific gravity corrected.
 See Supplemental Information for a detailed description of DHEA and
 testosterone during maturation. <em>Height
 Velocity. </em>Height velocity in 2014 was computed using height
 measurements collected 1-4 years prior to 2014, with the majority (70%)
 taken 2 years prior to the study. Height velocity was calculated
 as: Statistical
 analysis Analyses were performed in R version 4.1. Sex
 differences in participant characteristics were assessed using independent
 sample t-tests for continuous variables and Chi-square tests for
 distribution across Tanner stages. Spearman correlations were tested to
 validate Tanner stage with log transformed hormone levels (DHEA and
 testosterone which were both skewed) and measures of somatic growth and
 maturation (height velocity, grip strength, and body fat). Non-parametric
 tests were used because Tanner stage is ordinal, and body fat in males
 violated normality assumptions. To test P1 and P2, separate linear
 regression models were run for each activity outcome (sedentary time,
 light intensity PA, MVPA, steps/day) with age, sex, and the age x sex
 interaction included as independent variables. To test the mediating role
 of Tanner stage on age-sedentary/PA associations (P3), structural equation
 models (SEM) were fit in the lavaan package version 0.6-11 using listwise
 deletion for participants missing sedentary (n=4) or PA outcome data
 (n=6). Diagonally weighted least squares estimation was used to account
 for Tanner stage  being ordinal as opposed to continuous. Age and outcome
 variables were standardized to facilitate model convergence given the
 vastly different scales of the variables. Categorization and visual
 representation of self-reported PA was performed in R 2022.02.0 using the
 ggplot2 and lmer packages.  Validity of Tanner Stage with Hormone
 Levels and Somatic Maturation Markers Estimates of the
 within-sex Spearman correlations between Tanner stage assessment and DHEA,
 testosterone, height velocity, grip strength and body fat are presented in
 Supplemental Table 1. Tanner stage assessments were significantly
 correlated with all these variables in both sexes
 (<em>p</em>’s &lt; 0.01), with coefficients in females
 ranging from <em>r </em>= 0.46 for testosterone to <em>r
 </em>= -0.79 for height velocity and in males from
 <em>r</em> = -0.38 for height velocity to <em>r
 </em>= 0.92 for grip strength.
description: # Adolescence is characterized by more sedentary behavior and less
 physical activity even among highly active forager-farmers ## Tsimane
 joven [Access this dataset on Dryad] (doi:10.5061/dryad.4j0zpc8js) This
 file contains aggregated data for the full sample [grand\_total], with sex
 [female, male], and within-sex and Tanner stage [Female1 = female, Tanner
 1, etc.) as well as p-values resulting from tests of differences between
 males and females. ### Sharing/Access Information **Data Sharing and
 Materials Availability** [The Tsimane Health and Life History
 Project](https://tsimane.anth.ucsb.edu/) (THLHP) is a joint health and
 anthropology project aimed at understanding the impacts of ecology and
 evolution on the shaping of the human life course. The THLHP is conducted
 in partnership with the Tsimane and Moseten, indigenous forager-farming
 groups living in central lowland Bolivia in the Beni Department. It
 focuses on health, growth and development, aging, economics and
 biodemography of small-scale populations of hunter-gatherers and
 horticulturalists. The team combines biomedical and anthropological
 research with local Bolivian medical services. To perform these efforts
 requires a multidisciplinary, international team supported by diverse
 stakeholders. The THLHP’s highest priority is the safeguarding of human
 subjects and minimization of risk to study participants. Over and above
 individual safety, the THLHP adheres to the CARE Principles for Indigenous
 Data Governance. These Principles assure the Tsimane and Moseten 1) have
 sovereignty over how data are shared, 2) are the primary gatekeepers
 determining ethical use, 3) are actively engaged in the data generation
 and 4) derive benefit from data generated and shared use whenever
 possible. Pragmatically, the data are generated under the authority of the
 Tsimane (Gran Consejo Tsimane)/Moseten governments for use for specified
 research activities. Further guidance with respect to data access is often
 provided by research sponsors. The THLHP is committed to the FAIR
 Principles to facilitate data use with third parties. The THLHP is also
 committed to the FAIR Principles to facilitate data use. Requests for
 individual-level data should take the form of an application that
 minimally details the exact uses of the data and the research questions to
 be addressed, procedures that will be employed for data security and
 individual privacy, potential benefits to the study communities, and
 procedures for assessing and minimizing stigmatizing interpretations of
 the research results (see the following webpage for links to the data
 sharing policy and data request forms:
 [https://tsimane.anth.ucsb.edu/data.html](https://tsimane.anth.ucsb.edu/data.html). Requests for individual-level data will require institutional IRB approval (even if exempt) and will be reviewed by an Advisory Council composed of tribal leaders, tribal community members, Bolivian scientists, and the THLHP leadership. The study authors and the Tsimane leadership are committed to open science. ### Code/Software This repository contains code for replicating analysis in Caldwell, A., Cummings, D.K., Hooper, P., Trumble, B.C., Gurven, M., Stieglitz, J., Davis, H., Kaplan, H., Adolescence is characterized by more sedentary behavior and less physical activity even among highly active forager-farmers. Currently submitted to *Proceedings of the Royal Society B* This code was written by [Dan Cummings](https://github.com/dankcummings) and is available under Creative Commons [CC BY-NC-SA 4.0](https://creativecommons.org/licenses/by-nc-sa/4.0/). See LICENSE.md for details. | Variable name | | | ------------- | --- | | pid | PID | | Edad | Age | | Sexo | Sex | | wt | Wt | | ht | Ht | | ht\_velocity | HtVelocity | | EsfMano | GrStrength | | Tanner | Tanner | | X.BF | PercBF | | MeanRawDHEA | DHEA | | MeanRawT | T | | SumMinsSed | SedMins | | SumMinsLight\_full\_day | LightMinsFullDay | | SumMinsMVPA\_full\_day | MVPAMinsFullDay | | steps\_per\_day\_full\_day | StepsPerFullDay | | | | | | | | Unique to interview\_analysis data file | | Day | Day | | TotalTimeMins | TotalTimeMins | | ActivityDesc | ActivityDesc | | ActivityCode | ActivityCode | | Bin3Act | Intensity | | Bin3Purp | Type | | Bin3 | IntensityType |