Samson David R, Crittenden Alyssa N, Mabulla Ibrahim A, Mabulla Audax Z P, Nunn Charles L
Department of Evolutionary Anthropology, Duke University.
Department of Anthropology, University of Nevada, Las Vegas.
Am J Phys Anthropol. 2017 Mar;162(3):573-582. doi: 10.1002/ajpa.23160. Epub 2017 Jan 7.
Cross-cultural sleep research is critical to deciphering whether modern sleep expression is the product of recent selective pressures, or an example of evolutionary mismatch to ancestral sleep ecology. We worked with the Hadza, an equatorial, hunter-gatherer community in Tanzania, to better understand ancestral sleep patterns and to test hypotheses related to sleep segmentation.
We used actigraphy to analyze sleep-wake patterns in thirty-three volunteers for a total of 393 days. Linear mixed effects modeling was performed to assess ecological predictors of sleep duration and quality. Additionally, functional linear modeling (FLM) was used to characterize 24-hr time averaged circadian patterns.
Compared with post-industrialized western populations, the Hadza were characterized by shorter (6.25 hr), poorer quality sleep (sleep efficiency = 68.9%), yet had stronger circadian rhythms. Sleep duration time was negatively influenced by greater activity, age, light (lux) exposure, and moon phase, and positively influenced by increased day length and mean nighttime temperature. The average daily nap ratio (i.e., the proportion of days where a nap was present) was 0.54 (SE = 0.05), with an average nap duration of 47.5 min (SE = 2.71; n = 139).
This study showed that circadian rhythms in small-scale foraging populations are more entrained to their ecological environments than Western populations. Additionally, Hadza sleep is characterized as flexible, with a consistent early morning sleep period yet reliance upon opportunistic daytime napping. We propose that plasticity in sleep-wake patterns has been a target of natural selection in human evolution.
跨文化睡眠研究对于解读现代睡眠表现是近期选择性压力的产物，还是与祖先睡眠生态进化不匹配的一个例子至关重要。我们与坦桑尼亚赤道地区的狩猎采集社区哈扎人合作，以更好地了解祖先的睡眠模式，并检验与睡眠分段相关的假设。
我们使用活动记录仪分析了33名志愿者共393天的睡眠-觉醒模式。进行线性混合效应建模以评估睡眠时长和质量的生态预测因素。此外，使用功能线性建模（FLM）来表征24小时时间平均昼夜节律模式。
与工业化后的西方人群相比，哈扎人的睡眠特点是时长较短（6.25小时）、质量较差（睡眠效率 = 68.9%），但昼夜节律更强。睡眠时长受到更大的活动量、年龄、光照（勒克斯）暴露和月相的负面影响，而受到白昼长度增加和夜间平均温度的正面影响。平均每日午睡比例（即有午睡的天数比例）为0.54（标准误 = 0.05），平均午睡时长为47.5分钟（标准误 = 2.71；n = 139）。
这项研究表明，小规模觅食人群的昼夜节律比西方人群更受其生态环境的影响。此外，哈扎人的睡眠特点是具有灵活性，清晨睡眠时间一致，但依赖机会性的白天午睡。我们提出，睡眠-觉醒模式的可塑性在人类进化过程中一直是自然选择的目标。
