Gandhi Yetish

High resting metabolic rate among Amazonian forager-horticulturalists experiencing high pathogen burden

OBJECTIVES Resting metabolic rate (RMR) reflects energetic costs of homeostasis and accounts for 60 to 75% of total energy expenditure (TEE). Lean mass and physical activity account for much RMR variability, but the impact of prolonged immune activation from infection on human RMR is unclear in naturalistic settings. We evaluate the effects of infection on mass-corrected RMR among Bolivian forager-horticulturalists, and assess whether RMR declines more slowly with age than in hygienic sedentary populations, as might be expected if older adults experience high pathogen burden. MATERIALS AND METHODS RMR was measured by indirect calorimetry (Fitmate MED, Cosmed) in 1,300 adults aged 20 to 90 and TEE was measured using doubly labeled water (n = 40). Immune biomarkers, clinical diagnoses, and anthropometrics were collected by the Tsimane Health and Life History Project. RESULTS Tsimane have higher RMR and TEE than people in sedentary industrialized populations. Tsimane RMR is 18 to 47% (women) and 22 to 40% (men) higher than expected using six standard prediction equations. Tsimane mass-corrected TEE is similarly elevated compared to Westerners. Elevated leukocytes and helminths are associated with excess RMR in multivariate regressions, and jointly result in a predicted excess RMR of 10 to 15%. After age 40, RMR declines by 69 kcal/decade (p < .0001). Controlling for lean mass and height accounts for 71% of age-related RMR decline, and adding indicators of infection minimally affects the age slope. The residual level of age-related decline from age 40 is 1.2% per decade. CONCLUSION High pathogen burden may lead to higher metabolic costs, which may be offset by smaller body mass or other energy-sparing mechanisms.

What is segmented sleep? Actigraphy field validation for daytime sleep and nighttime wake

OBJECTIVE To compare different scoring parameter settings in actigraphy software for inferring sleep and wake bouts for validating analytical techniques outside of laboratory environments. DESIGN To identify parameter settings that best identify napping during periods of wakefulness, we analyzed 137 days on which participants reported daytime napping, as compared with a random subset of 30 days when no naps were reported. To identify settings that identify periods of wakefulness during sleep, we used data from a subsample of women who reported discrete wake bouts while nursing at night. SETTING Equatorial Tanzania in January to February 2016. PARTICIPANTS The Hadza-a non-industrial foraging population. MEASUREMENTS Thirty-three subjects participated in the study for 393 observation days. Using the Bland-Altman technique to determine concordance, we analyzed reported events of daytime napping and nighttime wake bouts. RESULTS Only 1 parameter setting could reliably detect reported naps (15-minute nap length, ≤50 counts). Moreover, of the 6 tested parameter settings to detect wake bouts, the setting where the sleep-wake algorithm was parameterized to detect 20 consecutive minutes throughout the designated sleep period did not overestimate or underestimate wake bouts, had the lowest mean difference, and did not significantly differ from reported wake-bout events. CONCLUSION We propose operational definitions for multiple dimensions of segmented sleep and conclude that actigraphy is an effective method for detecting segmented sleep in future cross-site comparative research. The implications of such work are far reaching, as sleep research in preindustrial and developing societies is documenting natural sleep-wake patterns in previously inaccessible environments.

Patterns of senescence in human cardiovascular fitness: VO2max in subsistence and industrialized populations

This study explores whether cardiovascular fitness levels and senescent decline are similar in the Tsimane of Bolivia and Canadians, as well as other subsistence and industrialized populations. Among Tsimane, we examine whether morbidity predicts lower levels and faster decline of cardiovascular fitness, or whether their lifestyle (e.g., high physical activity) promotes high levels and slow decline. Alternatively, high activity levels and morbidity might counterbalance such that Tsimane fitness levels and decline are similar to those in industrialized populations.

The influence of age- and sex-specific labor demands on sleep in Namibian agropastoralists

Objective: To understand the basics of sleep quality in a pastoralist population and to explore predictors of this variation. Design: Cross‐sectional. Setting: Northern Namibia, dry seasons of 2016 and 2017. Participants: The Himba, a nonindustrial seminomadic agropastoralist population without access to the electrical grid. Measurements: Using Actiwatch‐2 devices, 75 participants completed 721 days of wear. We calculated sleep duration, efficiency, and activity counts before and after sunset/sunrise and onset/offset. Participants were also interviewed about sleeping arrangements and nighttime disruptions. Results: Himba show lower sleep duration and efficiency than other populations studied, and men had substantially lower duration and efficiency than women. Sex differences were not attenuated when napping was included with total sleep time. Age predicted longer sleep duration and lower evening and morning activity levels. Number of adult co‐sleepers predicted increased sleep duration and efficiency in women. Livestock disturbance was not a commonly reported cause of nighttime waking. Conclusions: These findings support predictions that pastoralist groups may have lower sleep quality than other subsistence populations, but this does not appear to be a consequence of noise from livestock. Instead, lower sleep quality appears to be the result of subsistence and social activities, particularly for men and young adults overall.