Is daytime napping associated with inflammation in adolescents?

Sleep duration and the risk of new-onset arthritis in middle-aged and older adult population: results from prospective cohort study in China

Background

The pain and sleep disorders caused by arthritis are health issues that have been re-emphasized with the aging population. However, the majority of research on arthritis and sleep disorders has focused on cases that have already been diagnosed with arthritis. This research aims to explore the correlation between sleep duration and new-onset arthritis in middle-aged and older adult individuals.

Methods

Utilizing data from the China Health and Retirement Longitudinal Study from baseline (2011) to the Wave 3 follow-up (2018), we conducted a 7-year longitudinal investigation targeting populations with valid sleep questionnaire records and without arthritis. Sleep duration was assessed from nighttime sleep and daytime nap records. The new-onset of arthritis was determined based on self-reported diagnosis. We employed different logistic regression models to consider the potential impact of sleep duration on arthritis and conducted mediation analyses to assess the involvement of BMI in the association between sleep duration and the new-onset risk of arthritis.

Results

Out of the 6,597 individuals analyzed in the cohort, 586 (8.9%) were diagnosed with new-onset arthritis. Median sleep duration was notably shorter in the new-onset arthritis group (6.63 vs. 6.41 h, p < 0.05). There was a notable negative correlation found between new-onset risk of arthritis and sleep duration, with each Interquartile Range (IQR) increment in sleep leading to a 16% risk reduction (OR: 0.864; 95% CI: 0.784-0.954). Stratified analyses revealed BMI as a potential modifier in the sleep-arthritis relationship (P for interaction = 0.05). Mediation analyses further showed that about 3.5% of the association was mediated by BMI. Additionally, the inclusion of sleep duration improved the arthritis predictive power of our model, with an IDI of 0.105 (0.0203, 0.1898) and an NRI of 0.0013 (0.0004, 0.0022) after adding sleep duration to the basic model.

Conclusion

In the middle-aged and older adult demographic of China, increased sleep duration is associated with a decreased new-onset risk of arthritis, with BMI potentially playing a role in mediating this connection.

Family income as a moderator of relations between sleep and physical health during adolescence

OBJECTIVES

Sleep duration, quality, and consistency are associated with overall physical health in adolescence, yet the effects of sleep on development may be not uniform because both sleep and physical health vary systematically along gradients of family income. To understand "for whom" sleep may be particularly beneficial, the present study tested family income as a moderator of relations between youth sleep and physical health.

METHODS

Three hundred twenty-three youth (M age=17.39years; 53% female; 41% Black, 59% White) wore wrist actigraphs for 1week at home. Four well-recognized sleep parameters were derived: minutes, efficiency, long wake episodes, and variability in minutes across the week. Parents reported family income, and mothers rated adolescents' physical health. In independent path models, physical health was regressed onto each indicator of sleep, family income, and Sleep × Family Income interactions to test potential moderation effects.

RESULTS

Associations between sleep and physical health were moderated by family income. Lower sleep efficiency, more long wake episodes, and more variability in sleep minutes were associated with poorer physical health among adolescents from lower-income families. At optimal levels of all sleep variables, income-based differences in physical health were mitigated. Youth from higher-income families tended to have better physical health regardless of their sleep.

CONCLUSIONS

Findings build evidence that sleep has relations with physical health for low-income youth in particular. Clinicians and other service providers working with youth might benefit from considering the role of sleep in prevention and interventions programs geared toward improving health.

Association of night-time sleep duration and daytime napping with all-cause and cause-specific mortality in older British men: Findings from the British Regional HeartStudy

Short and long night-time sleep and daytime napping in young and middle-aged populations were associated with increased mortality, but it is unclear in very older people. The aim of this prospective study was to assess the associations in people aged >70 years. We examined the data of British Regional Heart Study, which included 1722 men aged 71-92 years and had night-time sleep duration and daytime napping measured at baseline and were followed up for nine years. There were 597 deaths. Compared to night-time sleep at 7-<8 h, age-adjusted hazard ratio of all-cause mortality in participants sleeping <6 h was 1.04 (95% CI 0.80-1.35), 1.07 (0.85-1.34) in 6-<7 h, 1.04 (0.83-1.30) in 8-<9 h and 0.93 (0.65-1.33) in ≥9 h. Further adjustments for other co-variables still showed no association, and neither the association with cardiovascular mortality nor non-cardiovascular mortality. Daytime napping, however, was associated with mortality. After adjustment for age, smoking, physical activity, obesity, cardiovascular diseases, diabetes, frailty, general health, anti-hypertensive medication and C-reactive protein level, hazard ratio of all-cause mortality in participants with daytime napping >1-h versus no napping was 1.62 (1.18-2.22) and hazard ratio of non-cardiovascular mortality was 1.77 (1.22-2.57). The fully adjusted hazard ratio of cardiovascular mortality was not significantly increased 1.26 (0.69-2.28), although age-adjusted hazard ratio was significant 1.94 (1.20-3.16). In the elderly men, daytime napping was independently associated with increased all-cause and non-cardiovascular mortality, while its association with cardiovascular mortality could be explained by cardiovascular risk factors and co-morbidities. Night-time sleep duration was not associated with mortality risk.

Sleep duration and daytime napping in relation to incident inflammatory bowel disease: a prospective cohort study

BACKGROUND

Sleep dysregulation has been linked to gastrointestinal dysfunction and inflammation.

AIMS

To explore the associations between sleep duration, daytime napping and inflammatory bowel disease (IBD), Crohn's disease (CD) and ulcerative colitis (UC).

METHODS

Exposure information was obtained from the baseline questionnaire. Sleep duration was coded as continuous and categorical (≤5, 6, 7, 8, ≥9 h/day) variables. Daytime napping was defined as yes (sometimes/usually) and no (never/rarely). Incident IBD cases were defined from primary care and hospital inpatient records. Polygenic risk scores (PRS) for the outcomes were constructed and categorised into low, intermediate and high risk. Hazard ratio (HR) and confidence interval (CI) were estimated using Cox proportional hazard regression.

RESULTS

The analysis included 2604 incident IBD cases (806 CD and 1798 UC) with a median follow-up of 12.0 years. Comparing sleep duration ≤5 with 7 h/day, the HR of IBD, CD and UC was 1.36 (95% CI, 1.17-1.59), 1.53 (95% CI, 1.17-2.00) and 1.29 (95% CI, 1.07-1.56), respectively. Comparing participants with and without daytime napping, the HR of IBD, CD and UC was 1.13 (95% CI, 1.05-1.23), 1.25 (95% CI, 1.08-1.44) and 1.09 (95% CI, 0.90-1.20), respectively. No interaction of sleep duration and daytime napping with PRS was detected.  However, the associations appeared stronger in individuals with high rather than low PRS.

CONCLUSIONS

This study reveals positive associations between short sleep duration and daytime napping and IBD risk.

Are adherence to the Mediterranean diet and siesta individually or jointly associated with blood pressure in Spanish adolescents? Results from the EHDLA study

Background

Both dietary and sleep patterns can influence both blood pressure levels and heart rate, but these associations have been understudied in adolescents. Furthermore, it is not known whether diet and sleep could exert a synergistic effect with respect to the maintenance of optimal BP levels in this population.

Objective

To investigate the relationship of blood pressure levels with the combination of higher adherence to the Mediterranean diet and the habit of siesta (daytime napping) in Spanish adolescents.

Methods

A cross-sectional study was conducted with data obtained through personal interviews and physical examination from a representative sample of 1,378 adolescents (12-17 years of age) from the Valle de Ricote (Region of Murcia, Spain) selected using a simple random sampling technique. Adherence to the Mediterranean diet was assessed with the Mediterranean Diet Quality Index in Children and Adolescents, and the frequency and duration of siesta were self-reported. Objective measurements of systolic and diastolic blood pressure were obtained under standardized conditions. Statistical procedures were performed with SPSS software (v.25) and included logistic and generalized regression models adjusted for sex, age, socioeconomic status, body mass index, total energy intake, nighttime sleep duration, and moderate-to-vigorous physical activity.

Results

Of the 698 adolescents finally studied (mean age 13.9 ± 1.5 years; 56.2% female), 37.1% (n = 259) had high adherence to the Mediterranean diet and 19.6% (n = 137) reported frequent siesta. In the completely adjusted models, compared to adolescents with low Mediterranean diet adherence and no or infrequent siesta, those with high Mediterranean diet adherence and frequent siesta were less likely to have high-normal blood pressure or hypertension (odds ratio = 0.47; 95% confidence interval: 0.26, 0.88) and showed slightly lower systolic blood pressure (ß-coef. = -2.60; 95% CI: -5.18, -0.02).

Conclusion

Greater adherence to the Mediterranean diet and frequent siesta have a synergistic effect on maintaining lower blood pressure levels in adolescence. These findings reinforce that adherence to both Mediterranean lifestyle behaviors early in life may be an important strategy to prevent hypertension throughout adulthood.

Cross-sectional and longitudinal associations between sleep duration, sleep quality, and bone stiffness in European children and adolescents

In this large perspective cohort among European children and adolescents, we observed that daytime napping was positively associated with bone stiffness, while short or long sleep duration combined with poor sleep quality was associated with less bone stiffness. Our findings are important for obtaining optimal bone stiffness in childhood.

INTRODUCTION

To examine the cross-sectional and longitudinal associations between sleep duration, sleep quality, and bone stiffness index (SI) in European children and adolescents.

METHODS

Four thousand eight hundred seventy-one children aged 2-11 years from the IDEFICS study and 861 children aged 6-15 years from the subsequent I.Family study were included. Sleep duration (i.e., nocturnal sleep and daytime napping) and sleep quality (i.e., irregularly bedtime routine, have difficulty falling asleep and trouble getting up in the morning) were reported by self-administrated questionnaires. Nocturnal sleep duration was converted into age-specific z-scores, and total sleep duration was classified into short, adequate, and long based on the National Sleep Recommendation. Calcaneal SI of both feet were measured using quantitative ultrasound. Linear mixed-effects models with country as a random effect were used, with adjustments for sex, age, pubertal status, family socioeconomic status, physical activity, screen time, body mass index, and daylight duration.

RESULTS

Nocturnal sleep duration z-scores were positively associated with SI percentiles among participants with adequate sleep duration at baseline. Moreover, the positive association between daytime napping and SI percentiles was more pronounced in participants with adequate sleep duration at baseline, while at 4-year follow-up was more pronounced in participants with short sleep duration. In addition, extreme sleep duration at baseline predicted lower SI percentiles after 4 years in participants with poor sleep quality.

CONCLUSION

The positive associations between nocturnal sleep, daytime napping and SI depended on total sleep duration. Long-term detrimental effect of extreme sleep duration on SI only existed in individuals with poor sleep quality.

Splitting sleep between the night and a daytime nap reduces homeostatic sleep pressure and enhances long-term memory

Daytime naps have been linked with enhanced memory encoding and consolidation. It remains unclear how a daily napping schedule impacts learning throughout the day, and whether these effects are the same for well-rested and sleep restricted individuals. We compared memory in 112 adolescents who underwent two simulated school weeks containing 8 or 6.5 h sleep opportunities each day. Sleep episodes were nocturnal or split between nocturnal sleep and a 90-min afternoon nap, creating four experimental groups: 8 h-continuous, 8 h-split, 6.5 h-continuous and 6.5 h-split. Declarative memory was assessed with picture encoding and an educationally realistic factual knowledge task. Splitting sleep significantly enhanced afternoon picture encoding and factual knowledge under both 6.5 h and 8 h durations. Splitting sleep also significantly reduced slow-wave energy during nocturnal sleep, suggesting lower homeostatic sleep pressure during the day. There was no negative impact of the split sleep schedule on morning performance, despite a reduction in nocturnal sleep. These findings suggest that naps could be incorporated into a daily sleep schedule that provides sufficient sleep and benefits learning.

Prevalence and predictors of metabolically healthy obesity in adolescents: findings from the national "Jeeluna" study in Saudi-Arabia

BACKGROUND

Obese children and adolescents may vary with respect to their health profile, an observation that has been highlighted by the characterization of metabolically healthy obesity (MHO). The objectives of this study were to examine the prevalence of MHO amongst obese adolescents in Saudi-Arabia, and investigate the anthropometric, socio-demographic, and lifestyle predictors of MHO in this age group.

METHODS

A national cross-sectional school-based survey (Jeeluna) was conducted in Saudi-Arabia in 2011-2012 (n = 1047 obese adolescents). Anthropometric, blood pressure and biochemical measurements were obtained. A multicomponent questionnaire covering socio-demographic, lifestyle, dietary, psychosocial and physical activity characteristics was administered. Classification of MHO was based on two different definitions. According to the first definition, subjects were categorized as MHO based on the absence of the following traditional cardiometabolic risk (CR) factors: systolic blood pressure (SBP) or diastolic blood pressure (DBP) >90th percentile for age, sex, and height; triglycerides (TG) > 1.25 mmol/L; high density lipoprotein-cholesterol (HDL-C) ≤1.02 mmol/L; glucose ≥5.6 mmol/L. The second definition of MHO was based on absence of any cardiometabolic risk factor, according to the International Diabetes Federation (IDF) criteria.

RESULTS

The prevalence of MHO ranged between 20.9% (IDF) and 23.8% (CR). Subjects with MHO were younger, less obese, had smaller waist circumference (WC) and were more likely to be females. Based on stepwise logistic regression analyses, and according to the IDF definition, body mass index (BMI) (OR = 0.89, 95% CI: 0.84-0.93) and WC (OR = 0.97, 95% CI: 0.96-0.98) were the only significant independent predictors of MHO. Based on the CR definition, the independent predictors of MHO included female gender (OR = 1.76, 95% CI: 1.29-2.41), BMI (OR = 0.97, 95% CI: 0.94-1.00), and weekly frequency of day napping (OR = 1.06, 95% CI: 1.00-1.12). Analysis by gender showed that vegetables' intake and sleep indicators were associated with MHO in boys but not in girls.

CONCLUSION

The study showed that one out of five obese adolescents is metabolically healthy. It also identified anthropometric factors as predictors of MHO and suggested gender-based differences in the association between diet, sleep and MHO in adolescents. Findings may be used in the development of intervention strategies aimed at improving metabolic heath in obese adolescents.

The Association between Daytime Napping Characteristics and Bone Mineral Density in Elderly Thai Women without Osteoporosis

Low bone mass is more prevalent with increasing age. Studies have found associations between sleep duration, sleep quality and obstructive sleep apnea and bone mineral density (BMD). However, less is known about the relationship between daytime napping and BMD. We aimed to investigate the association between daytime napping and BMD in elderly Thai women. Demographic data, lifestyle information and sleep characteristics were obtained by interviewing 387 elderly women. Weight and height were measured. Serum 25-hydroxyvitamin D [25(OH)D] was measured by radioimmunoassay. BMD was measured by dual-energy X-ray absorptiometry (DXA). Higher BMI and having type 2 diabetes (T2DM) were correlated with higher lumbar spine 2–4 (L2-4) BMD, while younger age, higher BMI and higher serum 25(OH)D level were correlated with higher femoral neck (FN) and total hip (TH) BMD. After adjusting for age, age at menopause, BMI, 25(OH)D level and T2DM, a higher frequency of weekly daytime napping was associated with lower FN and TH BMD but not at L2-4 BMD. Additionally, longer daytime napping duration was negatively associated with BMD at TH. In summary higher frequency and longer duration of daytime napping are associated with lower femoral BMD in elderly women. Mechanisms underlying these associations should be further explored.

A Systematic Review of Sleep, Hypertension, and Cardiovascular Risk in Children and Adolescents

PURPOSE OF REVIEW

Many of the risk factors for heart disease have recently been shown to develop during childhood such as left ventricular hypertrophy and fibrous plaque lesions. As risk for cardiovascular disease in children and adolescents has risen, sleep duration has decreased, and inadequate sleep in children and adolescents has been found to be associated with cardiovascular disease risk. The aims of this manuscript are to provide an updated systematic review of the literature assessing sleep, hypertension, and cardiovascular risk and evaluate the strength of the evidence based on the available research.

RECENT FINDINGS

A systematic review was conducted using six databases from January 1, 2015 through March 9, 2018. We sought studies which looked at the relationship between sleep duration, sleep timing, or sleep quality and outcome variables of hypertension, inflammation, obesity, glucose or insulin, and lipids in children and adolescents. We found 24 studies which met our criteria. Nine studies included hypertension as an outcome variable; fifteen included obesity; thirteen included glucose or insulin; eight included lipids; and three included measures of inflammation. The existing literature on sleep and cardiovascular disease in children and adolescents is limited and relatively weak. Only one RCT was identified, and the overwhelming majority of studies had a high risk of bias. The strongest evidence of an association with sleep is with obesity, hypertension, and insulin sensitivity. Further research using more standardized methods and objective measures is needed to determine if a causal relationship truly exists between sleep and cardiovascular risk.

Poor sleep moderates the relationship between daytime napping and inflammation in Black and White men

OBJECTIVES

To test whether napping was associated with 2 inflammatory markers with known relationships to cardiovascular disease: high-sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6). Because IL-6 is known to impact central inflammatory processes that relate to sleep regulation, including subjective fatigue, we tested whether this relationship was moderated by sleep duration, sleep efficiency, and self-reported sleep quality.

DESIGN

Cross-sectional.

PARTICIPANTS

A community sample of Black and White men (N=253) completed a week of actigraphy and diary measures of sleep and napping and provided a fasting blood sample.

MEASUREMENTS/ANALYSIS

Napping was measured as the proportion of days with at least 30 minutes napped and the average minutes napped per day. Linear regressions adjusted for race, socioeconomic status, employment, body mass index, smoking, medications that affect sleep or inflammation, working the nightshift, and day-sleeping status, followed by interaction terms between napping and sleep duration, efficiency, and quality, respectively.

RESULTS

There were no significant main effects of actigraphy- or diary-measured napping on IL-6 or hsCRP. Moderation analyses indicated elevated IL-6 values among men who napped more days (by actigraphy) and demonstrated short sleep duration (P=.03). Moderation analyses also indicated elevated IL-6 among men who demonstrated greater average minutes napped (by actigraphy) and short sleep duration (P<.001), low efficiency (P=.03), and poor quality (P=.03). Moderation analyses involving diary napping or hsCRP were not significant.

CONCLUSIONS

Actigraphy-assessed daytime napping is related to higher IL-6 in men who demonstrate worse sleep characteristics. Daytime napping may pose additional risk for inflammation beyond the known risk conferred by short sleep.