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

Hadza sleep biology: Evidence for flexible sleep‐wake patterns in hunter‐gatherers

“…If Hadza foragers are characterized by consolidated, non‐segmented sleep, we predict low frequency napping (exemplified by no difference between nighttime sleep duration and 24 hr sleep duration), nighttime wake‐bouts, and short wake after sleep onset (WASO). Additionally, if nocturnally bi‐phasic sleep is found, we predict clear overlap with another small‐scale society—Malagasy agriculturalists (Samson, Yetish, et al, ) —that are characterized by nocturnally bifurcated sleep‐wake patterns.…”

“…(c) A monophasic pattern is common in postindustrial economies with societal demands on activity from “9 am to 5 pm,” and non‐work related evening activity (Worthman, ). (d) A bifurcated pattern of nocturnal sleep bouts with supplemental daytime napping was the pattern evinced from a small scale, non‐electric, agricultural society in Madagascar (Samson, Manus, et al ). Image adapted from Miller, Matsangas, and Shattuck ()…”

“…The software also has a nap analysis function that detects periods of inactivity that are attributable to napping; specifically the software has adjustable parameters such as nap activity threshold and the minimum–maximum nap length . We used segmented sleep parameters that have been validated for field environments using actigraphy to assess daytime sleep (i.e., napping) and nighttime wakefulness (i.e., wake‐bouts), based on a study that compared reported, event marked events to actigraphy scored events using the Bland‐Altman technique to determine concordance (Samson, Yetish, et al, ). Nap activity threshold is the level at which the epoch within the specified period must be less than or equal to the entered value for the period to be scored as a nap; here, we used 50 counts as the threshold.…”

“…This approach, specifically designed for actigraphy time‐series data analysis, measures raw activity counts within and between samples, and avoids summary statistics that can mask differences across groups (Wang et al, ). FLM was used to compare activity patterns between the Hadza and an equatorial small‐scale, natural‐light, agricultural society in Madagascar that has previously been assessed as having nocturnally bi‐phasic sleep (Samson, Manus, et al, ). To this end, we applied a non‐parametric permutation test method in the R package “actigraphy” (Shannon et al, ), as it does not rely on distributional assumptions.…”

“…Historical records document a segmented sleep pattern associated with European preindustrial populations (Ekirch, ). Sleep measured in an equatorial, small scale‐agricultural society in Madagascar, without access to electricity, has been described as “segmented” or nocturnally biphasic with common noon‐time napping (Samson, Manus, et al, ). For example, statistical analysis in this population suggests the existence of a post‐midnight bump in activity, which has similarities to the “first” sleep and “second” sleep periods that have been suggested to exist in European societies before the availability of effective artificial light (Ekirch, ).…”