The association of sleep with physical and mental health among people experiencing homelessness.

BACKGROUND: Sleep deprivation is a critical risk factor for physical and mental health problems. The current study examined whether sleep problems were related to housing status and physical and mental health among people experiencing homelessness. METHODS: Data were collected via an anonymous survey completed by adults accessing services at a day shelter in Oklahoma City, OK. Demographic characteristics, sleep problems, days of poor physical and mental health, and self-rated health were assessed and compared across housing subgroups. Logistic regression analyses were performed to examine potential associations between sleep and health. RESULTS: Participants (N = 404) were predominantly male (71.0%) and racially minoritized (57.4%) with an average age of 47.0 (SD=11.6) years. Days of unintentional sleep over the past 30days differed significantly by housing status. Logistic regression analyses indicated that short sleep duration of ≤6 hours was associated with poorer self-rated health and more days of poor physical health over the past 30days compared to those who reported an optimal sleep duration of 7-9 hours. Additionally, reporting ≥1 day of unintentional daytime sleep was associated with more days of poor mental and physical health over the past 30-day. Reporting more days of inadequate sleep was associated with poorer self-rated health, and more days of poor physical and mental health over the past 30days. CONCLUSION: Sleep problems were associated with poorer physical and mental health among people experiencing homelessness. Safe environments where adults experiencing homelessness can sleep comfortably and without interruption may be needed to support good physical and mental health.

Evidence for an emotional adaptive function of dreams: a cross-cultural study.

The function of dreams is a longstanding scientific research question. Simulation theories of dream function, which are based on the premise that dreams represent evolutionary past selective pressures and fitness improvement through modified states of consciousness, have yet to be tested in cross-cultural populations that include small-scale forager societies. Here, we analyze dream content with cross-cultural comparisons between the BaYaka (Rep. of Congo) and Hadza (Tanzania) foraging groups and Global North populations, to test the hypothesis that dreams in forager groups serve a more effective emotion regulation function due to their strong social norms and high interpersonal support. Using a linear mixed effects model we analyzed 896 dreams from 234 individuals across these populations, recorded using dream diaries. Dream texts were processed into four psychosocial constructs using the Linguistic Inquiry and Word Count (LIWC-22) dictionary. The BaYaka displayed greater community-oriented dream content. Both the BaYaka and Hadza exhibited heightened threat dream content, while, at the same time, the Hadza demonstrated low negative emotions in their dreams. The Global North Nightmare Disorder group had increased negative emotion content, and the Canadian student sample during the COVID-19 pandemic displayed the highest anxiety dream content. In conclusion, this study supports the notion that dreams in non-clinical populations can effectively regulate emotions by linking potential threats with non-fearful contexts, reducing anxiety and negative emotions through emotional release or catharsis. Overall, this work contributes to our understanding of the evolutionary significance of this altered state of consciousness.

Hormone physiology and sleep dynamics among BaYaka foragers of the Congo Basin: Gendered associations between nighttime activity, testosterone, and cortisol.

Sleep quality is an important contributor to health disparities and affects the physiological function of the immune and endocrine systems, shaping how resources are allocated to life history demands. Past work in industrial and post-industrial societies has shown that lower total sleep time (TST) or more disrupted nighttime sleep are linked to flatter diurnal slopes for cortisol and lower testosterone production. There has been little focus on these physiological links in other socio-ecological settings where routine sleep conditions and nighttime activity demands differ. We collected salivary hormone (testosterone, cortisol) and actigraphy-based sleep data from Congolese BaYaka foragers (N = 39), who have relatively short and fragmented nighttime sleep, on average, in part due to their typical social sleep conditions and nighttime activity. The hormone and sleep data collections were separated by an average of 11.23 days (testosterone) and 2.84 days (cortisol). We found gendered links between nighttime activity and adults' hormone profiles. Contrary to past findings in Euro-American contexts, BaYaka men who were more active at night, on average, had higher evening testosterone than those with lower nighttime activity, with a relatively flat slope relating nighttime activity and evening testosterone in women. Women had steeper diurnal cortisol curves with less disrupted sleep. Men had steeper cortisol diurnal curves if they were more active at night. BaYaka men often hunt and socialize when active at night, which may help explain these patterns. Overall, our findings indicate that the nature of nighttime activities, including their possible social and subsistence contexts, are potentially important modifiers of sleep quality-physiology links, meriting further research across contexts.

Sound reasons for unsound sleep: Comparative support for the sentinel hypothesis in industrial and nonindustrial groups.

Background and objectives: Sleep is a vulnerable state in which individuals are more susceptible to threat, which may have led to evolved mechanisms for increasing safety. The sentinel hypothesis proposes that brief awakenings during sleep may be a strategy for detecting and responding to environmental threats. Observations of sleep segmentation and group sentinelization in hunter-gatherer and small-scale communities support this hypothesis, but to date it has not been tested in comparisons with industrial populations characterized by more secure sleep environments. Methodology: Here, we compare wake after sleep onset (WASO), a quantitative measure of nighttime awakenings, between two nonindustrial and two industrial populations: Hadza hunter-gatherers (n = 33), Malagasy small-scale agriculturalists (n = 38), and Hispanic (n = 1,531) and non-Hispanic White (NHW) (n = 347) Americans. We compared nighttime awakenings between these groups using actigraphically-measured sleep data. We fit linear models to assess whether WASO varies across groups, controlling for sex and age. Results: We found that WASO varies significantly by group membership and is highest in Hadza (2.44 h) and Malagasy (1.93 h) and lowest in non-Hispanic Whites (0.69 h). Hispanics demonstrate intermediate WASO (0.86 h), which is significantly more than NHW participants. After performing supplementary analysis within the Hispanic sample, we found that WASO is significantly and positively associated with increased perception of neighborhood violence. Conclusions and implications: Consistent with principles central to evolutionary medicine, we propose that evolved mechanisms to increase vigilance during sleep may now be mismatched with relatively safer environments, and in part responsible for driving poor sleep health.

Dreaming during the COVID-19 pandemic: Support for the threat simulation function of dreams.

Evolutionary theories suggest that dreams function as a world simulator of events that maximizes our ability to surmount social and threat-related challenges critical to survivorship and reproduction. Here, in contrast to the incorporation continuity hypothesis, we test the (1) social bias hypothesis, which states that dreams will overrepresent positive social interactions relative to waking life, (2) the mutually exclusive threat bias hypothesis, the idea that dream content will be negative relative to waking life, (3) the strengthening hypothesis, which states that dreams will rehearse more positive interactions with individuals the self is familiar with relative to waking life, and (4) the compensation hypothesis, which states that social contents in dreams increases during periods of social seclusion. Dream (n = 168) and wake (n = 184) reports were collected through a standardized online survey from 24 undergraduate students. Recalls were analyzed using the Social Content Scale. Generalized linear mixed effects models were used, and the following fixed-effects were considered for the study; the number of reports contributed, report state, biological sex, stress, social support, and media exposures. Results showed support for the threat bias hypothesis, we found that dreams were more negative and featured more unfamiliar individuals in contrast to waking life. Additionally, we found partial support for the social bias and the strengthening hypotheses, however no support was shown for the compensation hypothesis. Overall, these results demonstrate support for the threat simulation function of dreams.

Technological infrastructure, sleep, and rest-activity patterns in a Kaqchikel Maya community.

Sleep duration, quality, and rest-activity pattern-a measure for inferring circadian rhythm-are influenced by multiple factors including access to electricity. Recent findings suggest that the safety and comfort afforded by technology may improve sleep but negatively impact rest-activity stability. According to the circadian entrainment hypothesis, increased access to electric lighting should lead to weaker and less uniform circadian rhythms, measured by stability of rest-activity patterns. Here, we investigate sleep in a Maya community in Guatemala who are in a transitional stage of industrialization. We predicted that (i) sleep will be shorter and less efficient in this population than in industrial settings, and that (ii) rest-activity patterns will be weaker and less stable than in contexts with greater exposure to the natural environment and stronger and more stable than in settings more buffered by technologic infrastructure. Our results were mixed. Compared to more industrialized settings, in our study population sleep was 4.87% less efficient (78.39% vs 83.26%). We found no significant difference in sleep duration. Rest-activity patterns were more uniform and less variable than in industrial settings (interdaily stability = 0.58 vs 0.43; intradaily variability = 0.53 vs 0.60). Our results suggest that industrialization does not inherently reduce characteristics of sleep quality; instead, the safety and comfort afforded by technological development may improve sleep, and an intermediate degree of environmental exposure and technological buffering may support circadian rhythm strength and stability.

Links between household and family social dynamics with sleep profiles among BaYaka foragers of the Congo Basin.

Given the contributions of sleep to a range of health outcomes, there is substantial interest in ecological and environmental factors, including psychosocial contexts, that shape variation in sleep between individuals and populations. However, the links between social dynamics and sleep are not well-characterized beyond Euro-American settings, representing a gap in knowledge regarding the way that local socio-ecological conditions interrelate with sleep profiles across diverse settings. Here, we focused on data from a subsistence-level society in Republic of the Congo to test for links between the household/family social environment and sleep measures. Specifically, we used actigraphy-derived sleep data (N = 49; 318 nights) from two community locations (a village and rainforest camp) among BaYaka foragers, who are members of a remote, non-industrialized subsistence society in the Congo Basin. We drew on social dynamics that have been previously linked to sleep variation in Euro-American contexts, including: household crowding, same surface cosleeping, and marital conflict. We examined the following sleep measures: total sleep time (TST), total 24-h sleep time (TTST), and sleep quality (fragmentation). BaYaka adults had shorter and lower quality sleep when their shared sleeping space was more crowded. In the village, parents with breastfeeding-aged infants had longer TTST and higher quality sleep than adults without infants, contrasting with results from other cultural contexts. Based on peer rankings of marital conflict, husbands showed longer and higher quality sleep in less conflicted marriages. Women showed the opposite pattern. These counter-intuitive findings for women may reflect the limitations of the measurement for wives' marital experiences. In total, these results point to the importance of considering local socio-ecological conditions to sleep profiles and underscore the need for expanded study of sleep and health outcomes in settings where shared sleep in constrained space is routine practice.

The activity patterns of nonworking and working sled dogs.

There are limited studies investigating the combined effects of biological, environmental, and human factors on the activity of the domestic dog. Sled dogs offer a unique opportunity to examine these factors due to their close relationship with handlers and exposure to the outdoors. Here, we used accelerometers to measure the activity of 52 sled dogs over 30 days from two locations in Canada. The two locations differ in the working demands of dogs, therefore we used linear mixed effects models to assess how different factors impact daytime and nighttime activity of working versus nonworking dogs. During the daytime, we found that males were more active than females among nonworking dogs and younger dogs were more active than older dogs among working dogs. Alaskan huskies had higher activity levels than non-Alaskan husky breeds in working sled dogs during the day. Nonworking dogs were slightly more active during colder weather, but temperature had no effect on working dogs' activity. The strongest predictor of daytime activity in working dogs was work schedule. These results indicate that the influence of biological factors on activity varied depending on dogs' physical demands and human activity was the most powerful driver of activity in working dogs.

Enriched sleep environments lengthen lemur sleep duration.

Characteristics of the sleep-site are thought to influence the quality and duration of primate sleep, yet only a handful of studies have investigated these links experimentally. Using actigraphy and infrared videography, we quantified sleep in four lemur species (Eulemur coronatus, Lemur catta, Propithecus coquereli, and Varecia rubra) under two different experimental conditions at the Duke Lemur Center (DLC) in Durham, NC, USA. Individuals from each species underwent three weeks of simultaneous testing to investigate the hypothesis that comfort level of the sleep-site influences sleep. We obtained baseline data on normal sleep, and then, in a pair-wise study design, we compared the daily sleep times, inter-daily activity stability, and intra-daily activity variability of individuals in simultaneous experiments of sleep-site enrichment and sleep-site impoverishment. Over 164 24-hour periods from 8 individuals (2 of each species), we found evidence that enriched sleep-sites increased daily sleep times of lemurs, with an average increase of thirty-two minutes. The effect of sleep-site impoverishment was small and not statistically significant. Though our experimental manipulations altered inter-daily stability and intra-daily variability in activity patterns relative to baseline, the changes did not differ significantly between enriched and impoverished conditions. We conclude that properties of a sleep-site enhancing softness or insulation, more than the factors of surface area or stability, influence lemur sleep, with implications regarding the importance of nest building in primate evolution and the welfare and management of captive lemurs.

Gender differences in BaYaka forager sleep-wake patterns in forest and village contexts.

Sleep studies in small-scale subsistence societies have broadened our understanding of cross-cultural sleep patterns, revealing the flexibility of human sleep. We examined sleep biology among BaYaka foragers from the Republic of Congo who move between environmentally similar but socio-ecologically distinct locations to access seasonal resources. We analyzed the sleep-wake patterns of 51 individuals as they resided in a village location (n = 39) and a forest camp (n = 23) (362 nights total). Overall, BaYaka exhibited high sleep fragmentation (50.5) and short total sleep time (5.94 h), suggestive of segmented sleep patterns. Sleep duration did not differ between locations, although poorer sleep quality was exhibited in the village. Linear mixed effect models demonstrated that women's sleep differed significantly from men's in the forest, with longer total sleep time (ß ± SE = - 0.22 ± 0.09, confidence interval (CI) = [- 0.4, - 0.03]), and higher sleep quality (efficiency; ß ± SE = - 0.24 ± 0.09, CI = [- 0.42, - 0.05]). These findings may be due to gender-specific social and economic activities. Circadian rhythms were consistent between locations, with women exhibiting stronger circadian stability. We highlight the importance of considering intra-cultural variation in sleep-wake patterns when taking sleep research into the field.

Gibbon sleep quantified: the influence of lunar phase and meteorological variables on activity in Hylobates moloch and Hylobates pileatus.

Sleep in the primate order remains understudied, with quantitative estimates of sleep duration available for less than 10% of primate species. Even fewer species have had their sleep synchronously quantified with meteorological data, which have been shown to influence sleep-wake regulatory behaviors. We report the first sleep duration estimates in two captive gibbon species, the Javan gibbon (Hylobates moloch) and the pileated gibbon (Hylobates pileatus) (N = 52 nights). We also investigated how wind speed, humidity, temperature, lunar phase, and illumination from moonlight influence sleep-wake regulation, including sleep duration, sleep fragmentation, and sleep efficiency. Gibbons exhibited strict diurnal behavior with little nighttime activity and mean total average sleep duration of 11 h and 53 min for Hylobates moloch and 12 h and 29 min for Hylobates pileatus. Gibbons had notably high sleep efficiency (i.e., time score asleep divided by the time they spent in their sleeping site, mean of 98.3%). We found illumination from moonlight in relation to lunar phase and amount of wind speed to be the strongest predictors of sleep duration and high-quality sleep, with increased moonlight and increased wind causing more fragmentation and less sleep efficiency. We conclude that arousal threshold is sensitive to nighttime illumination and wind speed. Sensitivity to wind speed may reflect adaptations to counter the risk of falling during arboreal sleep.

Pandemic Nightmares: COVID-19 Lockdown Associated With Increased Aggression in Female University Students' Dreams.

The COVID-19 pandemic and its associated stressors have impacted the daily lives and sleeping patterns of many individuals, including university students. Dreams may provide insight into how the mind processes changing realities; dreams not only allow consolidation of new information, but may give the opportunity to creatively "play out" low-risk, hypothetical threat simulations. While there are studies that analyze dreams in high-stress situations, little is known of how the COVID-19 pandemic has impacted dreams of university students. The aim of this study was to explore how the dream content of students was affected during the university COVID-19 lockdown period (March-July, 2020). Using online survey methods, we analyzed dream recall content (n = 71) using the Hall-Van de Castle dream coding system and Fisher's exact tests for sex comparisons. Preliminary results indicate that female students experienced more nightmares as compared to male students. Dream analysis found that, relative to normative American College Student (ACS) samples generated pre-COVID-19, women were more likely to experience aggressive interactions in their dream content, including increased physical aggression. Results indicate that university students did experience changes in dream content due to the pandemic lockdown period, with women disproportionally affected. These findings can aid universities in developing support programs for students by bringing forth an understanding of students' concerns and anxieties as they process the "new normal" of social distancing.

Taking the sleep lab to the field: Biometric techniques for quantifying sleep and circadian rhythms in humans.

OBJECTIVES: Remarkably, the specifics of sleep along the human lineage have been slow to emerge, which is surprising given our distinct mental and behavioral capacity and the importance of sleep for individual health and cognitive performance. Largely due to difficultly of measuring sleep outside a controlled, clinical, and laboratory study in ambulatory individuals, human biologists have yet to undergo a thorough examination of sleep in ecologically diverse settings. Here, I outline the procedures and methods for generating sleep data in a broader ecological context with the goal of facilitating the integration of sleep and circadian analyses into human biology research. METHODS: I describe the steps involved in participant recruitment, screening by way of survey instruments, and sample collection. In addition to describing field use of the traditional (but invasive) equipment such as the gold-standard application of electroencephalography (EEG), I demonstrate leading-edge noninvasive techniques for biometric devices (ie, wrist-worn actigraphy, ring worn arterial pulsometry) to generate sleep and circadian rhythms data. RESULTS: I outline best approaches to process and analyze data-including variables such as sleep duration, 24-hour sleep time (ie, summation of night and day sleep), sleep efficiency, sleep fragmentation, and nonparametric circadian rhythms analysis to quantify circadian amplitude. Finally, I discuss comparative statistical methods that are optimized for the use of time-series data. CONCLUSIONS: This review serves as an introduction to the best practices for studying sleep-wake patterns in humans-with the goal of standardizing tools for launching new human sleep biology research initiatives across the globe.

A functional linear modeling approach to sleep-wake cycles in dogs.

The study of companion (pet) dogs is an area of great translational potential, as they share a risk for many conditions that afflict humans. Among these are conditions that affect sleep, including chronic pain and cognitive dysfunction. Significant advancements have occurred in the ability to study sleep in dogs, including development of non-invasive polysomnography; however, basic understanding of dog sleep patterns remains poorly characterized. The purpose of this study was to establish baseline sleep-wake cycle and activity patterns using actigraphy and functional linear modeling (FLM), for healthy, adult companion dogs. Forty-two dogs were enrolled and wore activity monitors for 14 days. FLM demonstrated a bimodal pattern of activity with significant effects of sex, body mass, and age; the effect of age was particularly evident during the times of peak activity. This study demonstrated that FLM can be used to describe normal sleep-wake cycles of healthy adult dogs and the effects of physiologic traits on these patterns of activity. This foundation makes it possible to characterize deviations from normal patterns, including those associated with chronic pain and cognitive dysfunction syndrome. This can improve detection of these conditions in dogs, benefitting them and their potential as models for human disease.

Sex differences in daily activity intensity and energy expenditure and their relationship to cortisol among BaYaka foragers from the Congo Basin.

OBJECTIVES: The pooling of energetic resources and food sharing have been widely documented among hunter-gatherer societies. Much less is known about how the energetic costs of daily activities are distributed across individuals in such groups, including between women and men. Moreover, the metabolic physiological correlates of those activities and costs are relatively understudied. MATERIALS AND METHODS: Here, we tracked physical activity, energy expenditure (EE), and cortisol production among Congo Basin BaYaka foragers engaged in a variety of daily subsistence activities (n = 37). Given its role in energy mobilization, we measured overall daily cortisol production and short-term cortisol reactivity through saliva sampling; we measured physical activity levels and total EE via the wGT3X-bt actigraph and heart rate monitor. RESULTS: We found that there were no sex differences in likelihood of working in common activity locations (forest, garden, house). Across the day, women spent greater percentage time in moderate-to-vigorous physical activity (%MVPA) and had lower total EE than men. Females with higher EE (kCal/hr) produced greater cortisol throughout the day. Though not statistically significant, we also found that individuals with greater %MVPA had larger decreases in cortisol reactivity. DISCUSSION: BaYaka women sustained higher levels of physical activity but incurred lower energetic costs than men, even after factoring in sex differences in body composition. Our findings suggest that the distribution of physical activity demands and costs are relevant to discussions regarding how labor is divided and community energy budgets take shape in such settings.

Sleep influences cognitive performance in lemurs.

Primates spend almost half their lives asleep, yet little is known about how sleep influences their waking cognition. We hypothesized that diurnal and cathemeral lemurs differ in their need for consistent, non-segmented sleep for next-day cognitive function-including long-term memory consolidation, self-control, foraging efficiency, and sociality. Specifically, we expected that strictly diurnal Propithecus is more reliant on uninterrupted sleep for cognitive performance, as compared to four other lemur species that are more flexibly active (i.e., cathemeral). We experimentally inhibited sleep and tested next-day performance in 30 individuals of 5 lemur species over 960 total nights at the Duke Lemur Center in Durham, North Carolina. Each set of pair-housed lemurs experienced a sleep restriction and/or deprivation protocol and was subsequently tested in a variety of fitness-relevant cognitive tasks. Within-subject comparisons of performance on these tasks were made by switching the pair from the experimental sleep inhibited condition to a normal sleep environment, thus ensuring cognitive equivalency among individuals. We validated effectiveness of the protocol via actigraphy and infrared videography. Our results suggest that 'normal' non-disrupted sleep improved memory consolidation for all lemurs. Additionally, on nights of normal sleep, diurnal lemurs performed better in foraging efficiency tasks than cathemeral lemurs. Social behaviors changed in species-specific ways after exposure to experimental conditions, and self-control was not significantly linked with sleep condition. Based on these findings, the links between sleep, learning, and memory consolidation appear to be evolutionarily conserved in primates.

Does the moon influence sleep in small-scale societies?

OBJECTIVES: The lunar cycle is expected to influence sleep-wake patterns in human populations that have greater exposure to the environment, as might be found in forager populations that experience few environmental buffers. We investigated this "moonlight" hypothesis in two African populations: one composed of hunter-gatherers (with minimal environmental buffering) and the other rural agriculturalists (with low-to-moderate environmental buffering). SETTING: Research was conducted on Hadza hunter-gatherers from the Sengele community near Lake Eyasi in northern Tanzania and in Mandena, Madagascar, in a rural community of approximately 4000 farmers. PARTICIPANTS: Thirty-one adult Hadza and 21 Malagasy adults were recruited. MEASUREMENTS: We used the CamNtech Motionwatch 8 actigraph and generated data on an epoch-by-epoch, 1-minute basis. RESULTS: In general support of the moonlight hypothesis, we uncovered an association between sleep-wake patterns and lunar cycle (ie., moonlight) for Hadza hunter-gatherers. However, the direction of the effect was opposite to what we predicted: as the potential for exposure to moonlight increased, activity generally shifted to a pattern of less nighttime activity and greater daytime activity. No significant effects were found in the Malagasy agriculturalists. CONCLUSIONS: The proposal that human behaviors are linked with moon phase is a popular belief that persists despite the absence of consistent evidence. We provide the first direct evidence that lunar cycle is linked to sleep-wake pattern in a hunter-gatherer society, suggesting that moonlight does not inhibit sleep-wake patterns in the ways that electric lighting does.

Infant co-sleeping patterns and maternal sleep quality among Hadza hunter-gatherers.

OBJECTIVE: Despite widespread interest in maternal-infant co-sleeping, few quantified data on sleep patterns outside of the cultural west exist. Here, we provide the first report on co-sleeping behavior and maternal sleep quality among habitually co-sleeping hunter-gatherers. DESIGN: Data were collected among the Hadza of Tanzania who live in domiciles constructed of grass huts with no access to synthetic lighting or climate controlled sleeping environments. Using interview data, we recorded baseline ethnographic data on co-sleeping. Using actigraph data, we tested whether sleep quality, sleep-wake activity, and/or sleep duration differs among breastfeeding women, non-breastfeeding women, and men. MEASUREMENTS: CamNtech Motionwatch 8 actigraphs were used to collect 1 minute, epoch-by-epoch data on a sample of 33 adults. Functional linear modeling (FLM) was used to characterize sleep-wake patterns and a linear mixed-effects model was used to assess factors that drive sleep duration and quality. RESULTS: The FLM suggests that breastfeeding mothers were early risers and had reduced day-time activity. Additionally, total number of co-sleepers, not breastfeeding, was associated with less sleep duration and quality, suggesting that greater number of co-sleepers may be a primary driver of poorer sleep. CONCLUSION: The current study makes important contributions to the cross-cultural literature on sleep and augments our understanding of maternal-infant co-sleeping. The majority of Hadza participants co-sleep with at least one other individual and the majority of married couples sleep with their spouse and their children on the same sleeping surface. Our preliminary sleep quality data suggest that breastfeeding does not negatively impact maternal sleep quality.

High prevalence of hypertension in an agricultural village in Madagascar.

Elevated blood pressure presents a global health threat, with rates of hypertension increasing in low and middle-income countries. Lifestyle changes may be an important driver of these increases in blood pressure. Hypertension is particularly prevalent in African countries, though the majority of studies have focused on mainland Africa. We collected demographic and health data from 513 adults living in a community in rural Madagascar. We used generalized linear mixed models to assess body mass index (BMI), age, sex, and attributes related to household composition and lifestyle as predictors of blood pressure and hypertension. The prevalence of hypertension in this cohort was 49.1% (both sexes combined: N = 513; females: 50.3%, N = 290; males: 47.5%, N = 223). Blood pressure, as well as hypertensive state, was positively associated with age and BMI. Lifestyle and household factors had no significant relationships with blood pressure. The prevalence of hypertension was similar to that found in urban centers of other African countries, yet almost double what has been previously found in Madagascar. Future research should investigate the drivers of hypertension in rural communities worldwide, as well as the lifestyle, cultural, and genetic factors that underlie variation in hypertension across space and time.

The cost of deep sleep: Environmental influences on sleep regulation are greater for diurnal lemurs.

OBJECTIVES: Primates spend almost half their lives asleep, yet we know little about how evolution has shaped variation in the duration or intensity of sleep (i.e., sleep regulation) across primate species. Our objective was to test hypotheses related to how sleeping site security influences sleep intensity in different lemur species. METHODS: We used actigraphy and infrared videography to generate sleep measures in 100 individuals (males = 51, females = 49) of seven lemur species (genera: Eulemur, Lemur, Propithecus, and Varecia) at the Duke Lemur Center in Durham, NC. We also generated experimental data using sleep deprivation for 16 individuals. This experiment used a pair-wise design for two sets of paired lemurs from each genus, where the experimental pair experienced a sleep deprivation protocol while the control experienced normal sleeping conditions. We calculated a sleep depth composite metric from weighted z scores of three sleep intensity variables. RESULTS: We found that, relative to cathemeral lemurs, diurnal Propithecus was characterized by the deepest sleep and exhibited the most disruptions to normal sleep-wake regulation when sleep deprived. In contrast, Eulemur mongoz was characterized by significantly lighter sleep than Propithecus, and E. mongoz showed the fewest disruptions to normal sleep-wake regulation when sleep deprived. Security of the sleeping site led to greater sleep depth, with access to outdoor housing linked to lighter sleep in all lemurs that were studied. CONCLUSIONS: We propose that sleeping site security was an essential component of sleep regulation throughout primate evolution. This work suggests that sleeping site security may have been an important factor associated with the evolution of sleep in early and later hominins.