Sleep Duration Variability Research Articles

Circulating metabolites associated with objectively measured sleep duration and sleep variability in overweight/obese participants: a metabolomics approach within the SATIN study.

To investigate the associations of circulating metabolites with sleep duration and sleep variability. We also assessed the ability of metabolites to discriminate between sleep duration and sleep variability categories. Cross-sectional analyses were performed on baseline data from 205 participants with overweight/obesity in the "Satiety Innovation" (SATIN) study. A targeted metabolite profiling (n = 159 metabolites) approach was applied using three different platforms (nuclear magnetic resonance, liquid chromatography coupled to mass spectrometry, and gas chromatography coupled to mass spectrometry). Associations between circulating metabolite concentrations and accelerometer-derived sleep duration and variability in sleep duration were assessed using elastic-net regression analysis. Ten-fold cross-validation was used to estimate the discriminative accuracy of metabolites for sleep duration and sleep variability categories. A metabolite profile, including acyl-carnitines (C11:0/C5:1-DC/iso-C11:0, 2-M-C4:1/3-M-C4:1, C4:0), sphingomyelins (42:1, 33:1), glycerol, stearic acid, 2- and 3- hydroxyl-butyric acid, docosahexaenoic acid, serotonin, and phosphatidylcholine (34:2), was significantly associated with high sleep duration (4th plus 5th quintile). Ten metabolites, including acyl-carnitines (C18:1, C7:0, C6-OH), phosphatidylcholine (40:6, 37:4, 42:5), lyso-phosphatidylcholine (20:1), sucrose, glutamic acid, and triacylglycerol (52:4), were significantly associated with high sleep variability (4th plus 5th quintile). The area under the curve was 0.69 (95% CI: 0.62-0.75) and 0.63 (95% CI: 0.53-0.72) in the multimetabolite score for high sleep duration and sleep variability, respectively. The variance in sleep duration explained by metabolites was 7%. No metabolites were selected for prediction of sleep variability (continuous). A small set of metabolites within distinct biochemical pathways were associated with high sleep duration and sleep variability. These metabolites appeared to moderately discriminate sleep duration and sleep variability categories.

Sleep duration and apolipoprotein B in metabolically healthy and unhealthy overweight/obese phenotypes: a cross-sectional study in Chinese adults

ObjectivesShort sleep duration is independently associated with an increased risk of developing cardiovascular disease; however, the association has not yet been examined in obese populations. We assessed the associations between...

Breakpoints of time in bed, midpoint of sleep, and social jetlag from infancy to early adulthood

ObjectivesThe present study investigated sleep duration and sleep timing from infancy to early adulthood. MethodsA cross-sectional survey study of N = 18,323 participants (9004 female) from 0 to 25 years (M = 12.36; SD = 5.76) from kindergartens, schools and universities in SW Germany. Participants reported their usual bedtimes and rise times on weekdays/weekends. Time in bed (TIB), the midpoint of sleep, and social jetlag were calculated from these four clock times. ResultsWeekday rise times were progressively earlier until the age of 17 years, while weekend rise times contrarily were later. As a consequence, TIB during the week was progressively shorter until the age of 16 years. The midpoint of sleep (MSFsc) was increasingly later until it reached a plateau at 17 years. Social jetlag increased until 16 years to 3:18 h. Gender differences were small for sleep duration/chronotype with males sleeping less and later than girls and non-significant for social jetlag. A regression with two breakpoints explained variability in sleep duration and sleep timing by age (45–61% explained variance) better than a regression with one breakpoint (44–59%), linear regression (25–54%) or polynomial regression (43–60%). ConclusionsThe age around 16–17 years can be considered a remarkable breakpoint when sleep behavior significantly changes back towards slightly longer sleep, less socially jetlagged behavior, and the increase in eveningness is then stopped but not reversed. A somewhat softer breakpoint is identified around 5–7 years when the rapid changes in sleep behavior initiate.

Responsiveness of Time and Cost-Efficient Monitoring Measures on Triathlon Training a Call for Individualized Training Monitoring

Objective: We aimed to assess the responsiveness of monitoring measures on cumulative training from the previous 1 up to 7 days in elite triathletes. Methods: Six male well-trained triathletes (31.8 ± 6.8 yrs, VO2max 70.5 ± 4.0 ml/kg/min) participated in a 9 weeks observational study during the pre-competition training period. Training load and time spent in different training intensity zones, morning measures of objective monitoring variables including resting heart rate, heart rate variability (HRV) and sleep duration and subjective monitoring variables including subjectively felt daily condition, energy level, willingness to train, muscle soreness, general stress, general fatigue and quality of sleep were assessed daily. Training data were retrospectively correlated with objective and subjective measures Results: On a group level, higher cumulative training time spent in high-intensity running but not swimming or cycling lead to moderate increase in muscle soreness (R=0.344 for 5-days cumulative high-intensity running, p=0.043), small increase in subjectively felt general stress (R=0.168 for 4-days. Cumulative high-intensity training time (cHITT), p=0.043 and R=0.221 for 6-days cHITT, p=0.043), a small decrease in daily condition (R=-0.113 for 7-days cHIIT, p=0.043) and willingness to train (R=-0.169 for 7-days cHIIT, p=0.043) but did not affect any objective monitoring variables.There were remarkable individual differences in correlations between cumulative training load, time spent in different training intensity zones and objective and subjective variables Conclusion: Since the responsiveness of objective and subjective monitoring parameters to training was very individual, not only training loads but also the selection of objective and subjective measures should be individualized for monitoring triathletes.

Shift work, sleep duration, and body image dissatisfaction among female workers in southern Brazil.

We examined the association between shift work and sleep duration with body image dissatisfaction (BID) among shift-working women in southern Brazil. In this cross-sectional study, data of 505 women shift workers, between 18 and 60years old, were collected between January and April 2011. BID was assessed using the Stunkard Figure Rating Scale. Information on shift work, sleep duration, and other explanatory variables was collected through a questionnaire. An aggregated exposure variable was created and termed "sleep deprivation," with the exposure category being night-shift workers who slept < 7h/day. The respective prevalence ratio values were estimated using a Poisson regression. The prevalence of BID among shift-working women was 42.4 (95% CIs = 38.0 to 46.7%), and 199 (93.0%) of these women wished they had a smaller body size. Shift work (PR = 1.40; p = 0.006) and sleep duration (PR = 1.32; p = 0.010) were independently associated with BID. Additionally, workers with sleep deprivation exhibited a higher probability of BID than those without sleep deprivation (PR = 1.31; p = 0.012). These results reveal a situation of vulnerability and the need for strategies and actions directed at shift-working women with the aim of reducing the effects of sleep deprivation on mental health, particularly with regard to body image disorders.

Family contexts and sleep during adolescence

Sleep deprivation among adolescents has received much attention from health researchers and policymakers. Recent research indicates that variation in sleep duration from night to night is associated with multiple health outcomes. While there is evidence that sleep deprivation is socially patterned, we know little about how social contexts are associated with nightly sleep variation during adolescence (a life course stage when nightly sleep variation is particularly high). Given the importance of family environments for influencing adolescents’ sleep patterns, we hypothesized that disadvantaged family contexts would be associated with higher intra-individual variation (IIV) in nightly sleep duration, in addition to lower average nightly sleep duration. We tested these hypotheses in a diverse, population-based sample of 11–17 year-olds (N = 1095) from the Adolescent Health and Development in Context Study. Using survey and ecological momentary assessment data and a novel form of multi-level regression modeling (location-scale mixed modeling), we found that adolescents living in unmarried-parent, low SES, economically insecure, and high caregiver stress families had higher IIV in sleep than adolescents in families with more resources and less caregiver stress. There were fewer family effects on average sleep duration. This suggests family social and economic contexts are associated with an under-researched aspect of adolescent sleep, nightly variation, and may contribute to adolescent sleep problems with implications for their health and health disparities.

Young adolescent sleep is associated with parental monitoring

ObjectivesInsufficient sleep can increase risk for adverse psychological and physical outcomes. Parental monitoring of daily activities is associated with youth health behaviors. We examined parental monitoring of waking and bedtime behaviors and sleep in a community sample of high-risk youth. MethodsOne-hundred sixty-five 10- to 14-year-olds from low–socioeconomic status families participated (11.8 years ±1.16, 52% female; 78% Black/African American). Parents and youth evaluated parental monitoring of waking activities. Parent expectations about bedtime and parent knowledge about adolescent's bedtime and sleep routine were independently rated. Youth sleep was assessed via parent report and actigraphy over 7 days. ResultsMore parental knowledge about bedtime was associated with longer parent-reported sleep duration (β = .18, P < .05). Parental monitoring of waking activities (youth reported) was associated with more actigraph-assessed sleep over 7 days (B = 2.73, SE = .91), weekdays (B = 2.44, SE = .01), and weekends (B = 3.88, SE = .1.41, all Ps < .05), whereas parent reported monitoring was associated with more sleep on weekdays only (B = 2.10, SE = .87, P < .05). Parental knowledge and expectations about bedtime behaviors were not associated with actigraph-assessed sleep (P values > .05). Parental monitoring of waking and bedtime behaviors was not associated with sleep duration variability (P values > .05). ConclusionsParental monitoring of waking activities may indirectly influence adolescent sleep via increased structure and felt security in the parent-adolescent relationship. Youth perception of monitoring may be particularly relevant for youth sleep duration.

Correlates of nocturnal sleep duration, nocturnal sleep variability, and nocturnal sleep problems in toddlers: results from the GET UP! Study

ObjectiveTo explore the correlates of nocturnal sleep duration, nocturnal sleep variability, and nocturnal sleep problems in a sample of Australian toddlers. MethodsParticipants were 173 toddlers (average age 19.7 ± 4.1 months) from the GET UP! Study. Nocturnal sleep duration, nocturnal sleep variability, nap(s) and physical activity were measured using 24-h accelerometry (Actigraph GT3X+) over seven consecutive days. Nocturnal sleep problems were assessed using the Tayside Children's Sleep Questionnaire. Screen time was reported by the parents. Logistic regression models were used to examine the associations between potential correlates (ie, age, sex, socio-economic status, weight status, physical activity, screen time, nap(s), bedtimes, and wake-up times) and nocturnal sleep characteristics. ResultsOlder children were more likely to have greater sleep variability (OR: 1.97; 95% CI: 1.08–3.61). Less physical activity (OR: 2.38; 95% CI: 1.27–4.45), shorter nap(s) (OR: 2.42, 95% CI: 1.29–4.55), and later wake-up times (OR: 4.42; 95% CI: 2.32–8.42) were associated with higher odds of having longer nocturnal sleep duration. Late bedtimes were associated with shorter nocturnal sleep duration (OR: 0.09; 95% CI: 0.04–0.18) and with greater nocturnal sleep variability (OR: 1.97; 95% CI: 1.06–3.68). None of the potential correlates were associated with nocturnal sleep problems. ConclusionThe present study identifies several correlates of nocturnal sleep duration (total physical activity, nap(s), bedtime, and wake-up time) and nocturnal sleep variability (age and bedtime), whereas no correlates were identified for nocturnal sleep problems. The association between late bedtimes and shorter nocturnal sleep duration and greater nocturnal variability suggests that these may be modifiable targets for future sleep interventions in early childhood. Trial registrationAustralian New Zealand Clinical Trials Registry: ACTRN12616000471482, 11/04/2016, retrospectively registered.

The Relationships between Life Satisfaction and Sleep Quality, Sleep Duration and Variability of Sleep in University Students

Life satisfaction and its relationship to aspects of sleep were investigated in 701 Norwegian university students using recreated sleep logs, questions about sleep-related experiences, a sleep quality item and the Satisfaction with Life Scale. The results indicated that better sleep quality, longer mean sleep duration, less variability in sleep duration and less variability in rise time were all associated with greater life satisfaction, but only sleep quality and variability of sleep duration were significant predictors of life satisfaction in a regression model. Consistent with previous research, the results emphasize the importance of sleep quality, and adds to existing research by suggesting that in some populations, variability of sleep duration might be more relevant to well-being than sleep duration itself.

Cross-sectional associations of objectively-measured sleep characteristics with obesity and type 2 diabetes in the PREDIMED-Plus trial.

To examine independent and combined associations of sleep duration and sleep variability with body composition, obesity and type 2 diabetes (T2D) in elders at high cardiovascular risk. Cross-sectional analysis of 1986 community-dwelling elders with overweight/obesity and metabolic syndrome from PREDIMED-Plus trial. Associations of accelerometry-derived sleep duration and sleep variability with body mass index (BMI), waist circumference (WC) and body composition were assessed fitting multivariable-adjusted linear regression models. Prevalence ratios (PR) and 95% confidence intervals (CI) for obesity and T2D were obtained using multivariable-adjusted Cox regression with constant time. "Bad sleepers" (age-specific non-recommended sleep duration plus sleep variability above the median) and "good sleepers" (age-specific recommended sleep duration plus sleep variability below the median) were characterized by combining sleep duration and sleep variability, and their associations with these outcomes were examined. One hour/night increment in sleep duration was inversely associated with BMI (β -0.38 kg/m2 [95% CI -0.54, -0.23]), WC (β -0.86 cm [95% CI -1.25, -0.47]), obesity (PR 0.96 [95% CI 0.93, 0.98]), T2D (PR 0.93 [95% CI 0.88, 0.98]) and other DXA-derived adiposity-related measurements (android fat and trunk fat, all p < .05). Each 1-hour increment in sleep variability was positively associated with T2D (PR 1.14 [95% CI 1.01, 1.28]). Compared with "good sleepers," "bad sleepers" were positively associated with obesity (PR 1.12 [95% CI 1.01, 1.24]) and T2D (PR 1.62 [95% CI 1.28, 2.06]). This study revealed cross-sectional associations of sleep duration with adiposity parameters and obesity. Sleep duration and sleep variability were associated with T2D. Considering simultaneously sleep duration and sleep variability could have additional value, particularly for T2D, as they may act synergistically.

Adiposity in Adolescents: The Interplay of Sleep Duration and Sleep Variability

To assess whether adiposity measures differed according to joint categories of sleep duration and sleep variability in a sample of Mexican adolescents. A sample of 528 Mexico City adolescents aged 9-17 years wore wrist actigraphs for 6-7 days. Average sleep duration was categorized as age-specific sufficient or insufficient. Sleep variability, the standard deviation of sleep duration, was split at the median into stable versus variable. Adiposity measures-body mass index (BMI)-for-age Z score (BMIz), triceps skinfolds, waist circumference, and percent body fat-were collected by trained assistants. We regressed adiposity measures on combined sleep duration and variability categories. Log binomial models were used to estimate prevalence ratios and 95% CI for obesity (>2 BMIz) by joint categories of sleep duration and variability, adjusting for sex, age, and maternal education. Approximately 40% of the adolescents had insufficient sleep and 13% were obese. Relative to sufficient-stable sleepers, adolescents with insufficient-stable sleep had higher adiposity across all 4 measures (eg, adjusted difference in BMIz was 0.68; 95% CI, 0.35-1.00) and higher obesity prevalence (prevalence ratio, 2.54; 95% CI, 1.36-4.75). Insufficient-variable sleepers had slightly higher BMIz than sufficient-stable sleepers (adjusted difference, 0.30; 95% CI, 0.00-0.59). Adolescents with consistently insufficient sleep could be at greater risk for obesity. The finding that insufficient-variable sleepers had only slightly higher adiposity suggests that opportunities for "catch-up" sleep may be protective.

Abstract 073: Sleep Duration and 24-hour Ambulatory Blood Pressure in Adults not on Antihypertensive Medications

Background: Short sleep duration has been widely linked to increased cardiovascular morbidity and mortality, although the underlying mechanisms for this relationship remain unclear. Maladaptive circadian variations in blood pressure (BP) may be an important mediator of adverse outcomes in people with short sleep duration. Our goal was to evaluate the association between sleep duration and 24-hour BP control. Methods: We performed a post-hoc analyses of 24-hour ambulatory BP monitoring in 219 non-hypertensive and pre-hypertensive adults in the Lifestyle Modification in BP Lowering Study (LIMBS) and Penn Icelandic Sleep Apnea (PISA) Study. Results: The 24-hour mean systolic BP was 12.7 mmHg higher in LIMBS (see Figure; p&lt;0.001) and 4.7 mmHg higher in PISA (p=0.005) among participants with shorter sleep duration (&lt;7 hours) compared to those with longer sleep duration (≥7 hours). There was a 1 mmHg higher 24-hour mean systolic BP for every 2.57 minute shorter sleep duration in LIMBS (95% CI -4.56 to -0.58; p&lt;0.001), and a 1 mmHg higher 24-hour mean systolic BP for every 1.99 minute shorter sleep duration in PISA (95% CI -3.48 to -0.50; p=0.009). There was no significant association between sleep duration and BP variability, nocturnal dipping, or in-office systolic BP. Conclusions: Shorter sleep duration is strongly associated with higher systolic BP on 24-hour ambulatory BP monitoring; the association seems to be independent of nocturnal and in-office BP. Adults with shorter sleep duration may benefit from screening with 24-hour ambulatory BP monitoring to promote earlier detection of hypertension and potentially mitigate their increased risk for future cardiovascular disease.

Early Life Socioeconomic Disparities in Children's Sleep: The Mediating Role of the Current Home Environment.

Despite identified concurrent socioeconomic disparities in children's sleep, little research has examined pathways explaining such associations. This study examined the quality of the home environment as a direct predictor of sleep and potential mediator of associations between early life socioeconomic status and objective and subjective indicators of sleep in middle childhood. A socioeconomically and ethnically diverse sample of 381 twin children (50% female; 46.6% lower middle class or living at or below the poverty line; 26% Hispanic/Latino) were assessed at 12 months for SES and eight years using gold-standard home environment interviews and actigraphy-measured sleep. Multilevel mediation path models indicated that lower early SES and lower quality concurrent home environments were associated with shorter sleep durations, longer sleep latencies, and greater sleep timing variability. The home environment significantly mediated associations with sleep duration and sleep timing variability. The findings illustrate an important target in the prevention of poor childhood and adolescent sleep.

Household chaos and family sleep during infants' first year.

Household chaos has been linked with dysregulated family and individual processes. The present study investigated linkages between household chaos and infant and parent sleep, a self-regulated process impacted by individual, social, and environmental factors. Studies of relations between household chaos and child sleep have focused on older children and teenagers, with little attention given to infants or parent sleep. This study examines these relationships using objective measures of household chaos and sleep while controlling for, respectively, maternal emotional availability at bedtime and martial adjustment, in infant and parent sleep. Multilevel modeling examined mean and variability of sleep duration and fragmentation for infants, mothers, and fathers when infants were 1, 3, 6, 9, and 12 months (N = 167). Results indicated infants in higher chaos homes experienced delays in sleep consolidation patterns, with longer and more variable sleep duration, and greater fragmentation. Parent sleep was also associated with household chaos such that in higher chaos homes, mothers and fathers experienced greater variability in sleep duration, which paralleled infant findings. In lower chaos homes, parents' sleep fragmentation mirrored infants' decreasingly fragmented sleep across the first year and remained lower at all timepoints compared to parents and infants in high chaos homes. Collectively, these findings indicate that after controlling for maternal emotional availability and marital adjustment (respectively) household chaos has a dysregulatory impact on infant and parent sleep. Results are discussed in terms of the potential for chaos-induced poor sleep to dysregulate daytime functioning and, in turn, place parent-infant relationships at risk. (PsycINFO Database Record

Sleep duration, lifestyles and chronic diseases: a cross-sectional population-based study.

BackgroundAdequate sleep is essential for health. Both, short and long sleep durations are associated to worse quality of life and poor health outcomes. Portugal represents a specific population model, since according to European statistics it has high rates of chronic diseases like depression, hypertension, diabetes and stroke; and low quality of life as well as low index of physical activity, while in parallel it has some other good health indicators such as: low age-standardized mortality for both genders, nutrition in terms of energy and fruit consumption, smoking and alcohol, obesity and overweight prevalence. The aim of this study was to characterize health and chronic diseases, lifestyles and quality of life in subjects with short and long sleep duration.MethodsA population-based cross-sectional evaluation of the third wave of follow-up of the EpiDoC Cohort was carried between 2015-2016. A sample of 5,436 adults ≥18 years, representative of the national population, self-reported their daily total sleep time. Associations between short sleep duration (SSD ≤5h), long sleep duration (LSD≥9h) and independent variables were determined.ResultsThe prevalence for SSD was high (20.7%) and the LSD (5.9%) was low. Being older, with lower education, retired and unemployed were associated to SSD and LSD (p<0.01). Being obese was associated to SSD as well as hypertension, gastrointestinal disease and hypercholesterolemia (p<0.01). SSD and LSD, were associated with diabetes (p<0.01 and p=0.03) and depression (p<0.01 and p=0.02) respectively. Cardiovascular disease (p<0.01) was associated to LSD. Multimorbidity (p<0.01) was associated to SSD. Worse quality of life and bad physical function were associated to SSD and LSD, as well as being hospitalized in the previous 12 months (p<0.01).ConclusionsSocio-demographic, physical activity and chronic diseases were associated to reduction and extension of sleep duration. There was no association between rheumatic diseases and cancer with sleep duration, as found in other studies. This study emphasizes the burden of self-reported SSD for Portugal, its consequences to health and the need to increase sleep awareness campaigns enhancing the importance of sleep in health. Furthermore, it emphasizes that chronic diseases risks are dependent on multiple parameters which varying in different countries or regions, imply the need of regional studies and interventions.

Factors influencing on health-related quality of life in South Korean with chronic liver disease

BackgroundThe objective of this study was to determine health-related quality of life (HRQoL) among chronic liver disease (CLD) subjects in South Korea using EuroQol five-dimension questionnaire (EQ-5D).MethodThe sample consisted of 139 subjects with CLD from the sixth Korean National Health and Nutrition Examination Survey (KNHNES VI). Data were analyzed using SPSS program for descriptive statistics, t-test, ANOVA, Scheffe’s test and hierarchical multiple regression.ResultsResults indicated that marital status (P < 0.01), occupation (P < 0.01), basic livelihood security recipient status (P < 0.05), hepatocellular carcinoma (P < 0.05), subjective health status (P < 0.01), and depression (P < 0.001) were significant predictors of HRQoL. Health behaviors (alcohol intake, sleep duration) variables were insignificant.ConclusionIn conclusion, marital status, occupation, basic livelihood security recipient status (BLSRS), hepatocellular carcinoma (HCC), subjective health status (SHS), and depression were confirmed to be factors affecting the HRQoL. We should be provide to continuous monitoring and education of adequate alcohol intake for patients with CLD. Findings of this study might be used to develop community based health programs and policies for CLD.

Impact of shift work schedules on actigraphy-based measures of sleep in Hispanic workers: results from the Hispanic Community Health Study/Study of Latinos ancillary Sueño study.

To describe sleep characteristics of shift workers compared with day workers from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) Sueño ancillary study and test the hypothesis that shift work is associated with shorter sleep duration, worse sleep quality, greater sleep variability, and other sleep/health-related factors. Employed adults (N = 1253, mean age 46.3 years, 36.3% male) from the Sueño study were included. Measures of sleep duration, timing, regularity, and continuity were calculated from 7 days of wrist-activity monitoring. Participants provided information on demographics, employment, work schedule (day, afternoon, night, split, irregular, and rotating), sleepiness, depressive symptoms, medications, caffeine, and alcohol use. Survey linear regression adjusting for age, sex, background, site, number of jobs, and work hours was used. In age and sex-adjusted models, all shift work schedules were associated with delayed sleep timing. Night and irregular schedules were associated with shorter sleep duration, greater napping, and greater variability of sleep. Afternoon and rotating shifts were associated with lower sleep regularity. In fully adjusted models, night and irregular schedules remained associated with shorter sleep duration, later sleep midpoint, and greater variability in sleep measures compared with day schedules. Split schedules were associated with, less time in bed, less sleep fragmentation, and less wake during the sleep period than day schedules. Work schedule significantly affects sleep-wake with substantial differences between day work and other types of schedule. Detailed assessment of work schedule type not just night shift should be considered as an important covariate when examining the association between sleep and health outcomes.

Sleep variability and nighttime activity among Tsimane forager-horticulturalists.

A common presumption in sleep research is that "normal" human sleep should show high night-to-night consistency. Yet, intra-individual sleep variation in small-scale subsistence societies has never been studied to test this idea. In this study, we assessed the degree of nightly variation in sleep patterns among Tsimane forager-horticulturalists in Bolivia, and explored possible drivers of the intra-individual variability. We actigraphically recorded sleep among 120 Tsimane adults (67 female), aged 18-91, for an average of 4.9 nights per person using the Actigraph GT3X and Philips Respironics Actiwatch 2. We assessed intra-individual variation using intra-class correlations and average deviation from each individual's average sleep duration, onset, and offset times ( ɛ¯). Only 31% of total variation in sleep duration was due to differences among different individuals, with the remaining 69% due to nightly differences within the same individuals. We found no statistically significant differences in Tsimane sleep duration by day-of-the-week. Nightly variation in sleep duration was driven by highly variable sleep onset, especially for men. Nighttime activities associated with later sleep onset included hunting, fishing, housework, and watching TV. In contrast to nightly sleep variation in the United States being driven primarily by "sleeping-in" on weekends, Tsimane sleep variation, while comparable to that observed in the United States, was driven by changing "bedtimes," independent of day-of-the-week. We propose that this variation may reflect adaptive responses to changing opportunity costs to sleep/nighttime activity.

Sleep duration and C-reactive protein: Associations among pregnant and non-pregnant women

Pregnant women experience more sleep disturbances and greater systemic inflammation than non-pregnant women. However, the few studies that have examined the links between sleep and inflammation in pregnant women have been in clinical samples. We examined whether sleep duration is associated with C-reactive protein (CRP) levels, a marker of inflammation, in pregnant and non-pregnant women in a population-based sample of US women. Participants were 2865 women of reproductive age (aged 20–44 years) in the National Health and Nutrition Examination Survey (NHANES), a nationally representative sample of Americans. Sleeping <5 h on weeknights or workdays was significantly associated with increased CRP levels among both pregnant and non-pregnant women in unadjusted analyses; however, after adjustment for demographic, and health-related variables (depressive symptoms, self-rated health status, body mass index (BMI), diabetes), sleeping <5 h was no longer significantly related to CRP levels. Pregnant women had significantly higher CRP levels, after adjusting for sleep duration, demographic, and health-related variables. Our findings suggest that pregnancy is associated with increased peripheral CRP, after adjustment for sleep duration, demographic, and health factors. Further, in both pregnant and non-pregnant U.S. women of reproductive age, short sleep duration is associated with higher CRP levels, but this link is explained by self-rated health, BMI, and diabetes. Further studies are needed to investigate links of other sleep parameters (e.g., sleep fragmentation) with CRP in these populations.

Sleep habits in adolescents with type 1 diabetes: Variability in sleep duration linked with glycemic control.

To describe adolescents' sleep on school and weekend nights using multiple methods and to examine the links between sleep variability, quality, and duration with diabetes indicators. Adolescents with type 1 diabetes (N = 65, mean age = 15.0, 52.3% female, mean HbA1c = 8.9% or 74 mmol/mol) wore an actigraph and kept daily diaries recording sleep, activities, and blood glucose monitoring (BGM) habits for at least 7 days. Average daily BGM and blood glucose (BG) levels were obtained through glucometer downloads. HbA1c was obtained as part of clinic visits. Adolescents completed a sleep quality questionnaire (Pittsburgh sleep quality index [PSQI]), and adolescents and caregivers reported on adherence to diabetes treatment. Adolescents reported a mean PSQI global score of 5.37, which is above the clinical cutoff for poor sleep quality. Actigraphy data revealed that mean adolescent total sleep time was 6:54 (h:min), and participants slept more on weekend nights than on school nights (P < .001). Additionally, variability in sleep duration was significantly related to HbA1c, frequency of BGM, and average BG. Total sleep time and self-reported sleep quality were not significantly associated with adherence or glycemic control. Few adolescents with type 1 diabetes met recommendations for sleep duration, and many reported poor sleep quality. We identified significant associations between variability in sleep duration with poorer glycemic control and less frequent BGM, supporting the need to consider sleep patterns as a modifiable factor that may affect adherence and glycemic control.