Impacts of nocturnal breastfeeding, photoperiod, and access to electricity on maternal sleep behaviors in a non-industrial rural Bolivian population

Does breastfeeding influence sleep? A longitudinal study across the first two postpartum years

BACKGROUND

The association between breastfeeding and sleep of the gestational parent is poorly understood. This longitudinal study investigated how breastfeeding is associated with total nighttime sleep duration and sleep efficiency (percentage of total sleep time in bed) in nulliparous participants over the first two postpartum years.

METHODS

Nulliparous participants (N = 155, M_age  = 33.45, SD_age  = 3.50) self-reported patterns of breastfeeding via telephone interviews and sleep via self-report at 1.5, 3, 6, 12 and 24 months postpartum. Data were analyzed using mixed-effects models, with breastfeeding variables as predictors and sleep variables as outcomes, controlling for relevant covariates.

RESULTS

Neither the presence of breastfeeding nor the percentage of human milk in infants' total diets was significantly associated with participants' sleep duration or sleep quality (P-values > 0.08). This finding held after controlling for the number of nighttime feeds (P-values > 0.11). However, greater numbers of nighttime feeds, regardless of feeding content, were strongly associated with shorter sleep duration and poor sleep efficiency (P-values < 0.05). On average, with each additional nighttime feed, nocturnal sleep duration decreased by 6.6-8.4 minutes, and sleep efficiency decreased by 2.88%-3.02%.

CONCLUSIONS

Data from this study showed that breastfeeding per se was not associated with shorter or poor nocturnal sleep, but the number of nighttime feeds was. Sharing nighttime infant care amongst different carers in the household could help reduce postpartum sleep disturbance and ameliorate its negative impact on wellbeing.

Socioeconomic impacts on Andean adolescents’ growth

Background/Objectives

We evaluated potential socioeconomic contributors to variation in Andean adolescents’ growth between households within a peri-urban community undergoing rapid demographic and economic change, between different community types (rural, peri-urban, urban) and over time. Because growth monitoring is widely used for assessing community needs and progress, we compared the prevalences of stunting, underweight, and overweight estimated by three different growth references.

Methods

Anthropometrics of 101 El Alto, Bolivia, adolescents (Alteños), 11.0–14.9 years old in 2003, were compared between households (economic status assessed by parental occupations); to one urban and two rural samples collected in 1983/1998/1977, respectively; and to the WHO growth reference, a representative sample of Bolivian children (MESA), and a region-wide sample of high-altitude Peruvian children (Puno).

Results

Female Alteños’ growth was positively associated with household and maternal income indices. Alteños’ height averaged ∼0.8SD/∼0.6SD/∼2SDs greater than adolescents’ height in urban and rural communities measured in 1983/1998/1977, respectively. Overweight prevalence was comparable to the WHO, and lower than MESA and Puno, references. Stunting was 8.5/2.5/0.5 times WHO/MESA/Puno samples, respectively.

Conclusions/Implications

Both peri-urban conditions and temporal trends contributed to gains in Alteños’ growth. Rural out-migration can alleviate migrants’ poverty, partly because of more diverse economic options in urbanized communities, especially for women. Nonetheless, Alteños averaged below WHO and MESA height and weight medians. Evolved biological adaptations to environmental challenges, and the consequent variability in growth trajectories, favor using multiple growth references. Growth monitoring should be informed by community- and household-level studies to detect and understand local factors causing or alleviating health disparities.

The Human Sleep Paradox: The Unexpected Sleeping Habits of Homo sapiens

The human sleep pattern is paradoxical. Sleep is vital for optimal physical and cognitive performance, yet humans sleep the least of all primates. In addition, consolidated and continuous monophasic sleep is evidently advantageous, yet emerging comparative data sets from small-scale societies show that the phasing of the human pattern of sleep–wake activity is highly variable and characterized by significant nighttime activity. To reconcile these phenomena, the social sleep hypothesis proposes that extant traits of human sleep emerged because of social and technological niche construction. Specifically, sleep sites function as a type of social shelter by way of an extended structure of social groups that increases fitness. Short, high-quality, and flexibly timed sleep likely originated as a response to predation risks while sleeping terrestrially. This practice may have been a necessary preadaptation for migration out of Africa and for survival in ecological niches that penetrate latitudes with the greatest seasonal variation in light and temperature on the planet.

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.

Community, household, and individual correlates of sleep behaviors in Guyanese female youth

OBJECTIVES

Chronic sleep loss among youth is a worldwide health problem. Since research on its predictors is often limited to high-income countries, it is unclear if these findings are generalizable to all populations. To address this gap from an ecological perspective, we evaluated the associations between adolescents' sleep behaviors and several factors at the community, household, and individual levels in a middle-income country.

METHODS

This was a cross-sectional study of 73 girls (mean age = 14.5 y; range = 11-18 y) in rural and urban communities in Guyana. Sleep behaviors (nap-duration, bedtime, rise-time, night-bed-duration, and sleep-duration) were assessed with interviews and monitored up to 7 consecutive days using waist-worn accelerometers.

RESULTS

Similar to other settings, Guyanese urban youth reported significantly later bedtimes than rural youth, and increasing age was associated with later bedtime and shorter night-bed-duration. In contrast to the association observed in high-income countries, increasing household poverty scores in Guyana were associated with longer night-bed-duration.

CONCLUSIONS

Although the relationships between locale, age, and sleep in Guyana paralleled patterns seen in high-income countries, the positive relationship between poverty and sleep diverges from previous reports. These findings suggest that predictors of chronic sleep loss seen in high-income countries are likely to differ from those in middle- and low-income countries. More sleep studies in underrepresented populations are needed to gain a comprehensive understanding of adolescent sleep behavior and its correlates.