Nap Duration Research Articles

Day-to-day dynamics of associations between sleep, napping, fatigue, and the cortisol diurnal rhythm in women diagnosed as having breast cancer.

To examine whether day-to-day variations in sleep behaviors, ongoing sleep disturbance, and fatigue predict the cortisol diurnal rhythm in women recently diagnosed as having early-stage breast cancer. Women (N = 130, mean [standard deviation] age = 55.6 [9.4] years) collected saliva 5×/day/2 days for cortisol. Diaries were used to assess prior-day nap duration, nocturnal awakenings, sleep latency, and morning restfulness. Ongoing fatigue and sleep disturbance were measured using the Multidimensional Fatigue Symptom Inventory and the Pittsburg Sleep Quality Inventory. Data were analyzed using a multilevel growth curve modeling. Greater ongoing fatigue (b = 0.035, p = .032), or sleep disturbance (b = 0.026, p = .006) predicted a slower cortisol decline. Greater ongoing fatigue also predicted higher awakening cortisol (b = 0.154, p = .030) and lower cortisol awakening response (CAR; b = -0.146, p = .005). Longer prior-day naps predicted higher CAR (b = 0.042, p = .050) and a steeper cortisol decline (b = -0.035, p = .003). Longer sleep latency predicted both a greater cortisol linear decline (b = -0.013, p < .001) and a greater quadratic slope curvature (b = 0.0007, p < .001). Feeling less rested in the morning predicted lower awakening cortisol (b = -0.187, p = .004), higher CAR (b = 0.124, p = .016), and a slower cortisol decline (b = 0.023, p = .042). Both daily variations in sleep behaviors and ongoing sleep disturbance and fatigue are associated with a disrupted cortisol rhythm. In contrast, prior-day napping is associated with a more robust cortisol rhythm. These findings are particularly relevant to women with breast cancer who often experience sleep disturbance and fatigue. Additional research is needed to determine causal pathways between sleep disturbance and dysregulation of the hypothalamic-pituitary-adrenal axis in patients with breast cancer.

Associations between longer habitual day napping and non-alcoholic fatty liver disease in an elderly Chinese population.

ContextBoth longer habitual day napping and Non-Alcoholic Fatty Liver Disease (NAFLD) are associated with diabetes and inflammation, but the association between day napping and NAFLD remains unexplored.ObjectiveTo investigate the association between the duration of habitual day napping and NAFLD in an elderly Chinese population and to gain insight into the role of inflammatory cytokines in this association.Design and SettingWe conducted a series of cross-sectional studies of the community population in Chongqing, China, from 2011 to 2012.ParticipantsAmong 6998 participants aged 40 to 75 years, 6438 eligible participants were included in the first study and analyzed to observe the association between day napping duration and NAFLD. In a separate study, 80 non-nappers and 90 nappers were selected to identify the role of inflammatory cytokines in this association. Logistic regression models were used to examine the odds ratios (ORs) of day nap duration with NAFLD.ResultsDay nappers had a significantly higher prevalence of NAFLD (P<0.001). Longer day napping duration was associated in a dose-dependent manner with NAFLD (P trend <0.001). After adjustment for potential confounders, the ORs were 1.67 (95% CI 1.13–2.46) for those reporting 0.5–1 h and 1.49 (95% CI 1.01–2.19) for those reporting >1 h of day napping compared with individuals who did not take day naps (all P<0.05). Longer-duration day nappers had higher levels of IL-6 and progranulin (PGRN) but lower levels of Secreted frizzled-related protein-5 (SFRP5, all P trend <0.001). After adjusting for IL-6, PGRN, and SFRP5, the association between day napping duration and NAFLD disappeared (all P>0.05).ConclusionLonger day napping duration is associated with a higher prevalence of NAFLD, and inflammatory cytokines may be an essential link between day napping and NAFLD.

Association of napping and night-time sleep with impaired glucose regulation, insulin resistance and glycated haemoglobin in Chinese middle-aged adults with no diabetes: a cross-sectional study

ObjectiveTo assess associations between napping and night-time sleep duration with impaired glucose regulation, insulin resistance (IR) and glycated haemoglobin (HbA1c).DesignCross-sectional study.SettingFujian Province, China, from June 2011 to January 2012.ParticipantsThis study...

After lunch naps reduce the afternoon motor activity of 4-5-year old enrolled in full-time childcare

Objective. To determine the relationship between napping and the afternoon motor activity of preschool-aged children. Method. Par­ticipants were 42 healthy 4-5-year olds from two child care centers (CCCs) - one where children could choose whether or not to nap after lunch (CCC I) and another one where all children were encouraged to do so (CCC II). Each participant wore an actigraphy watch for seven days so that their sleep/wake cycle and afternoon motor activity were objectively measured. In order to compare the children´s mean afternoon motor activity on napping and non-napping days, all chil­dren were required not to nap on at least one weekday. Results. The children´s mean afternoon motor activity was negatively correlated to their mean nap duration (r=-0.46; p&lt;0.05 ). The mean motor activity was smaller on nap days compared to non-nap days for the CCC II (t = -2.33; p&lt;0.03) but not for the CCC I (t=0.96; p=0.35). Conclu­sion. After lunch naps reduce the afternoon motor activity of 4-5- year olds enrolled in full-time child care.

Cochilos reduzem a atividade motora de crianças de 4-5 anos que frequentam creches em período integral

Objective. To determine the relationship between napping and the afternoon motor activity of preschool-aged children. Method. Par­ticipants were 42 healthy 4-5-year olds from two child care centers (CCCs) - one where children could choose whether or not to nap after lunch (CCC I) and another one where all children were encouraged to do so (CCC II). Each participant wore an actigraphy watch for seven days so that their sleep/wake cycle and afternoon motor activity were objectively measured. In order to compare the children´s mean afternoon motor activity on napping and non-napping days, all chil­dren were required not to nap on at least one weekday. Results. The children´s mean afternoon motor activity was negatively correlated to their mean nap duration (r=-0.46; p&lt;0.05 ). The mean motor activity was smaller on nap days compared to non-nap days for the CCC II (t = -2.33; p&lt;0.03) but not for the CCC I (t=0.96; p=0.35). Conclu­sion. After lunch naps reduce the afternoon motor activity of 4-5- year olds enrolled in full-time child care.

Associations between sleep duration, daytime nap duration, and osteoporosis vary by sex, menopause, and sleep quality.

Associations between sleep, daytime nap duration, and osteoporosis remain uncertain, and far less is even known about the influence of sex, menopause, and sleep quality on them. The objective of the study was to test the associations between sleep, daytime nap duration, and osteoporosis and whether they vary by sex, menopause, and sleep quality. This cross-sectional study was based on two communities in China. A total of 8688 participants (3950 males and 4738 females) aged 40 years or older were enrolled in the study. Self-reported sleep duration, daytime nap duration, sleep quality, and calcaneus bone mineral density were recorded. Sleep duration of 8-9 h/d and nap duration of 0 min/d were regarded as reference values. In postmenopausal women, risks (odds ratio and 95% confidence interval) of osteoporosis for sleep durations of 7-8 h/d, 9-10 h/d, and 10 h/d or longer were 1.531 (1.106, 2.121), 1.360 (1.035, 1.787), and 1.569 (1.146, 2.149), respectively (P < .05), and risks of osteoporosis for daytime nap durations of 30-60 min/d and longer than 60 min/d were 1.553 (1.212-1.989) and 1.645 (1.250-2.165), respectively (P < .05). However, a significant difference was not consistently observed in men or premenopausal women, regardless of sleep or daytime nap duration. As for sleep quality, positive results were seen most remarkably in postmenopausal females with good sleep. Sleep durations of 7-8 h/d, 9-10 h/d, and 10 h/d or longer, as well as longer daytime napping times, tend to present higher risks of having osteoporosis, and this tendency is most obvious in postmenopausal women reporting good-quality sleep.

Association between the amount of daytime sleep variability and cognitive flexibility in older adults

Introduction Disrupted sleep patterns are commonly referred in the older population. They are often manifested by decreased total sleep time, increased waking after sleep onset, and napping. Napping may also be associated with increased risk of cognitive impairment, particularly compromised executive function, like cognitive flexibility. Recent evidence showed that variability in nap duration from day to day was predictive of greater medical morbidity. The aim of the study is to assess the association between variability in the amount of daytime and nighttime sleep and cognitive flexibility in older adults. Materials and methods Participants were 76 subjects: 72% were women and mean age was 75.4 ± 3.9 years (1). Motor activity was recorded continuously for a week with actigraphs (Actiwatch-16/64) worn in the nondominant wrist, yielding estimates of the amount of daytime and nighttime sleep. The variability of daytime and nighttime sleep amounts were calculated by dividing the standard deviation of sleep amounts within the week by the square root of the number of data points. Participants also performed the Stroop test: the words red, blue and green and a string of Xs were displayed on a monitor in red, blue, or green color. Three keys from the computer keyboard were covered by corresponding color patches, and the participants were told to press the key corresponding to the color of the target. The color words served as stimuli in the incongruent condition (e.g., the word red displayed in blue color), and was considered as the cognitive flexibility. We obtained the reaction time (RTI) and percentage of correct responses (PCI) for incongruent stimuli. 1. Reyes S, Algarin C, Bunout D, Peirano P. Sleep/wake patterns and physical performance in older adults. Aging Clin Exp Res 2013;25:175–181. Results The logistic regression model showed that subjects with greater variability in the amount of daytime sleep were more likely to have longer RTI (OR = 1.07, p p Conclusion Our results show an association between daytime sleep amount variability and cognitive flexibility in older subjects. They provide support to the hypothesis relating sleep patterns and cognitive functioning, and suggest the relevance of daytime duration regularity for cognitive performance. Acknowledgements Support: FONIS SA06I20038/Fondecyt 1110513; (*) CONICYT, PhD program fellowship.

Tasimelteon treatment entrains the circadian clock and demonstrates significant benefit on sleep and wake parameters in totally blind individuals with non-24 hour circadian rhythms

The majority of totally blind individuals exhibit non-24-h circadian rhythms due to light signals not reaching the suprachiasmatic nucleus, resulting in Non-24-h Sleep–Wake Disorder (Non-24), a serious circadian rhythm disorder with no approved treatment. Tasimelteon is a novel circadian regulator in development for Non-24 with selective agonist activity for melatonin MT1 and MT2 receptors. Two phase III placebo-controlled studies in blind Non-24 patients assessed safety, efficacy and maintenance of effect of tasimelteon treatment (20 mg/day). Circadian period was assessed from urinary 6-sulfatoxymelatonin (aMT6s) and cortisol. Clinical assessments included a Non-24 Clinical Response Scale (N24CRS), nighttime sleep, daytime naps and Clinical Global Impression of Change (CGIC). Entrainment Study (SET) ( n = 84): Tasimelteon entrained the circadian clock (aMT6s: 20.0% vs. 2.6%; cortisol: 17.5% vs. 2.6%), had more clinical responders on the N24CRS (23.7 vs. 0%), improved CGIC (2.6% vs. 3.4), increased sleep in the worst quartile of nights (LQ-nTST) (57% vs. 17 min), and decreased nap duration in the worst quartile of days (UQ-dTSD) (46% vs. 18 min), compared to placebo ( p < 0.05). Maintenance Study (RESET) ( n = 20): Tasimelteon-entrained patients were randomized to continued treatment or placebo. Tasimelteon maintained entrainment compared to placebo (aMT6s: 90% vs. 20%; cortisol: 80% vs. 20%). In treated patients, nighttime sleep (LQ-nTST) increased, and daytime sleep (UQ-dTSD) decreased, by 67 and 59 min/day, respectively ( p < 0.05). During the run-in phase of the study, the rate of entrainment among tasimelteon treated patients ranged from 55% to 75% in subpopulation sensitivity analysis. Tasimelteon was safe and well-tolerated in both studies. Tasimelteon entrained the circadian pacemaker in blind patients with Non-24, and caused significant clinical improvement in multiple measures of sleep, wake and global functioning. Discontinuation of tasimelteon abolished circadian entrainment, resulting in an hour less sleep each night and an hour more sleep each day. These studies demonstrate that tasimelteon is an effective circadian regulator, and that continued treatment is required to maintain entrainment and the resulting clinical benefits. Support for the study was provided by Vanda Pharmaceuticals Inc. (ClinicalTrials.gov NCT01163032 and NCT01430754). Statistical and Analytical Support was provided by Dennis Fisher at ”P Less Than” company.

Nighttime Sleep, Daytime Napping, and Labor Outcomes in Healthy Pregnant Women in Taiwan

We prospectively examined the associations of nighttime and daytime sleep during the third trimester of pregnancy with labor duration and risk of cesarean deliveries in a convenience sample of 120 nulliparous women who completed sleep-related questionnaires and wore wrist actigraphs for up to 7 days. Nap duration and 24-hour sleep duration were inversely associated with labor duration in women with vaginal delivery. Neither actigraphy-derived nor self-reported sleep variables were associated with type of delivery (e.g., vaginal, cesarean). Results showed a beneficial effect of sleep on labor duration and suggest that studies of sleep duration effects on labor and pregnancy outcomes require a consideration of the amount of both daytime and nighttime sleep.

Longer habitual afternoon napping is associated with a higher risk for impaired fasting plasma glucose and diabetes mellitus in older adults: results from the Dongfeng–Tongji cohort of retired workers

ObjectivesAfternoon napping is a common habit in China. We used data obtained from the Dongfeng–Tongji cohort to examine if duration of habitual afternoon napping was associated with risks for impaired fasting plasma glucose (IFG) and diabetes mellitus (DM) in a Chinese elderly population. MethodsA total of 27,009 participants underwent a physical examination, laboratory tests, and face-to-face interview. They were categorized into four groups according to nap duration (no napping, <30, 30 to <60, 60 to <90, and ⩾90min). Logistic regression models were used to examine the odds ratios (ORs) of napping duration with IFG and DM. ResultsOf the participants, 18,515 (68.6%) reported regularly taking afternoon naps. Those with longer nap duration had considerably higher prevalence of IFG and DM. Napping duration was associated in a dose-dependent manner with IFG and DM (P<.001). After adjusting for possible confounders, longer nap duration (>60min; all P<.05) was still significantly associated with increased risk for IFG, and longer nap duration (>30min) was associated with increased risk for DM; however, this finding was not significant in the group with a nap duration of 60–90min. ConclusionsLonger habitual afternoon napping was associated with a moderate increase for DM risk, independent of several covariates. This finding suggests that longer nap duration may represent a novel risk factor for DM and higher blood glucose levels.

Changes in sleep habits and knowledge after an educational sleep program in 12th grade students

The objective of this research was to evaluate the effect of an education program using the meaningful learning approach on sleep knowledge and habits of 12th grade students. Thirty-four student volunteers (aged 16.8 _ 0.6 years) were divided into intervention (Sleep Education Program — SEP) and control groups. Sleep knowledge and habits were assessed by the “health and sleep” questionnaire. Also, the students filled out a sleep diary and the Karolinska Sleepiness Scale by one week (Stage 1). These procedures were repeated 3 weeks after the SEP (Stage 2) that was evaluated by a questionnaire. The SEP consisted of five 50-minute classes to discuss the physiological and behavioral processes of sleep and healthy lifestyle. At Stage 2, the intervention group increased the percentage of correct responses in 63% of the questions. On weekdays, they increased time in bed by 26 min, woke up 11 min later and showed a tendency to go to bed 18 min earlier (P = 0.07). On weekends, they advanced bedtime and wake-up times. These changes were associated with decreased irregularity at bedtimes and wake up times. These results were not observed in the control group, except the advance on wake up time on weekends. The frequency and duration of naps and daytime sleepiness levels did not differ between the stages for both groups. The SEP increased knowledge and contributed to positive changes in the adolescents’ sleep-wake cycle (SWC). However, daytime sleepiness levels remained unchanged probably due to an insufficient reduction on sleep deprivation to decrease its negative consequences.

Napping in English preschool children and the association with parents’ attitudes

Age-independent variability in childrens' napping duration may be influenced by parental preference and attitudes and childrens' availability or lack of opportunity to nap. Our study examined English preschool childrens' napping duration, frequency and location, and the association of daily nap duration with parents' attitudes towards napping. Parents of three-year-old children in deprived and nondeprived areas of a town in North-East England were interviewed regarding their attitudes towards child napping and completed four-day and five night sleep diaries documenting their childrens' daytime and nighttime sleep. Of 84 children, half had at least one nap during the four-day study period (median [interquartile range] daily nap duration across all children was 1 [21] min; for nappers only was 21 [34] min). Naps tended to be infrequent and short and few (6%) occurred in a bedroom. Children whose parents allowed or encouraged napping had significantly longer daily nap duration (n=25, median [interquartile range] daily nap duration 21 [34] min) compared to those whose parents tried to prevent them from napping (n=29, 1 [21] min), and those whose parents reported that children did not want to nap (n=30, 0 [0] min) (U=23.21; p<.001). Positive parental attitude towards napping was associated with longer child nap duration. Napping appeared to be mainly sporadic and opportunistic and was negatively perceived and prevented by one-third of parents. The consequences of premature nap cessation are not known; given the importance of sufficient sleep in childhood, we should possibly consider enabling young children to nap more freely.

Excessive Daytime Sleepiness in Taiwanese People With Heart Failure

Excessive daytime sleepiness can increase heart failure (HF) mortality, cause poor medication adherence, and worsen quality of life in people with HF. Recognition of excessive daytime sleepiness can help improve HF management outcomes. This study was designed to identify the determinants of daytime sleepiness in patients with HF in Taiwan. A cross-sectional and correlational study design was employed. We used nonprobability sampling to recruit 133 participants during their regular visits to a cardiovascular outpatient department of a medical center. Instruments used included the Epworth Sleepiness Scale, Symptom Subscale of Kansas City Cardiomyopathy Questionnaire, and Pittsburgh Sleep Quality Index. Excessive daytime sleepiness occurred in 23.3% of study participants. Significant determinants of excessive daytime sleepiness were daytime dysfunction, body mass index, and HF symptom frequency. Use of angiotensin-converting enzyme inhibitors was correlated with excessive daytime sleepiness but was not identified as a determinant. Approximately one quarter of participants reported subjective excessive daytime sleepiness, suggesting that recognition of this symptom should be incorporated into HF management. Interventions for improving daytime dysfunction, decreasing body mass index, and ameliorating HF symptoms may help improve excessive daytime sleepiness. Habitual daytime napping may assist Taiwanese patients with chronic HF to overcome poor nocturnal sleep and restore energy. However, extra daytime sleep and changes in the duration and pattern of daytime napping during the HF trajectory should be recognized early to maintain daytime functioning. Medical treatments may help control HF symptoms. Optimizing medications to minimize adverse effects may help patients maintain better treatment adherence.

Reduced Sleep Duration and Daytime Naps in Pregnant Women in Taiwan

Napping is highly prevalent in pregnant women, but the relation between nighttime sleep and daytime naps in pregnant women is poorly understood. The aim of this study was to examine the temporal association of nighttime sleep quality and quantity with subsequent daytime naps and the temporal association of daytime naps with sleep quality and quantity the following night in women during the third trimester of pregnancy in Taiwan. Sleep was assessed in 80 Taiwanese nulliparous women aged 31.70 years (SD = 4.58 years) using actigraphy and diaries for 7 consecutive days. Subjective sleep quality was examined using the Pittsburgh Sleep Quality Index. Multiple linear regressions with generalized estimating equations were used to examine the temporal associations of nighttime sleep and daytime naps. All women napped sometime during the study week, and mean Pittsburgh Sleep Quality Index global score was 6.6, indicating poor sleep quality. Fewer weekly work hours and shorter sleep duration the preceding night were associated with longer nap duration the next day. More work hours, longer nap duration, and more intense fatigue were associated with shorter sleep duration the following night. Naps during pregnancy might indicate insufficient nighttime sleep, and longer daytime naps could compromise subsequent nighttime sleep. Further research is needed to determine if short sleep duration and longer daytime naps are associated with negative pregnancy outcomes.

Sleep-disordered breathing and daytime napping are associated with maternal hyperglycemia

Sleep disturbances in pregnancy may impair glucose mechanism. This study aimed to examine associations of sleep-disordered breathing, sleep, and nap duration with 1-h glucose challenge test (GCT) levels in pregnant women after controlling for known risk factors for gestational diabetes. This is a case-control study of 104 pregnant women. All women underwent full polysomnography and a GCT and completed the multivariable apnea prediction and Pittsburgh Sleep Quality indexes. The primary outcome was maternal hyperglycemia measured by GCT. Bivariate and multivariable logistic regression analyses were performed. Over 13 % subjects reported habitual snoring in the first trimester. Only 9.3 % women with normoglycemia (GCT < 135) were habitual snorers, whereas 45.5 % women with hyperglycemia (GCT ≥ 135) had habitual snoring (p < 0.001). Sleep-disordered breathing symptoms (loud snoring, snorting/gasping, and apneas) (odds ratio (OR) 2.85; 95 % confidence interval (CI) 1.50-5.41; p = 0.001) and total nap duration (OR 1.48; 95 % CI 0.96-2.28; p = 0.08) were associated with hyperglycemia. After adjusting for confounders, sleep-disordered breathing symptoms (OR 3.37; 95 % CI 1.44-8.32; p = 0.005) and nap duration (OR 1.64; 95 % CI 1.00-2.681.02; p = 0.05) continued to be associated with hyperglycemia. However, the primary exposure measure, the apnea/hypopnea index in the first trimester was not significantly associated with hyperglycemia (OR 1.03; 95 % CI 0.83-1.28; p = 0.77). Sleep-disordered breathing symptoms and nap duration are associated with hyperglycemia. Sleep duration was not associated with hyperglycemia. Research is needed concerning whether women with sleep-disordered breathing and/or daytime napping are at risk for gestational diabetes.

Evaluation of an individual sleep intervention programme in people undergoing peritoneal dialysis treatment

This study aimed to evaluate effects of a non-pharmacological intervention on sleep, activity and fatigue in patients receiving peritoneal dialysis by the use of both actigraphy registration and self-assessed questionnaires. Insomnia is estimated to affect up to 60% of haemo- and peritoneal dialysis patients. It is associated with two common uremic symptoms, pruritus and restless legs syndrome. To our knowledge, no interventions have been evaluated by actigraphy. A prospective multiple baseline single-case experimental design. Two women and seven men with sleep problems, 48-77 years, treated with PD participated in a 17-week study from January 2009 to February 2011. Two interventions were separately implemented. First, a pressure-relieving mattress and second, a four week individual sleep hygiene and sleep scheduling intervention. The two interventions were evaluated both objectively by actigraphy and subjectively by questionnaires. A total of 315 sleep-wake cycles from nine individuals were evaluated. Three patients improved clinically significantly in five or more of the nine outcomes, i.e. sleep onset latency, nocturnal sleep duration, numbers and duration of napping, movement and fragmentation index, number of steps, metabolic equivalent unit, sleep efficiency and fatigue. The other six patients also showed improvements but to a lesser degree. Physical activity advice was the intervention that yielded most sleep improvements. This study illuminates the need for regular assessment of sleep and tiredness. It also demonstrates how a non-pharmacological treatment and self-management can be applied with renal supportive care to improve sleep quality. This study is a clinical example of a non-pharmacological intervention with supportive care and self-management. This model can improve health and reduce the pharmacological burden because hypnotics can be replaced by sleep hygiene self-care activities.

Gender differences in nighttime sleep and daytime napping as predictors of mortality in older adults: The Rancho Bernardo Study

Many studies suggest optimal sleep duration for survival is 7-8h/night. We report the gender-specific independent association of all-cause mortality with nighttime sleep and daytime nap duration in older adults who were followed for up to 19years. Between 1984 and 1987, 2001 community-dwelling, mostly retired, adults (1112 women), age 60-96years, answered questions about health, mood, medications, life-style, daytime napping, and nighttime sleep duration. Vital status was confirmed for 96% through July 2001. At baseline, men reported significantly longer nighttime sleep and daytime napping than women. In both men and women, nighttime sleep <6h was associated with depressed mood and sleep-related medication, and ⩾9h was associated with more alcohol consumption. Napping ⩾30min was associated with prevalent depressed mood, coronary heart disease, and cancer. Of the group, 61% died over the next 19years, at an average age of 85.6years. Mortality risk was lowest among those sleeping 7-7.9h/night in both men and women. Multiple-adjusted analyses showed that increased mortality was associated with nighttime sleep ⩾9h in women (HR 1.51: 95% CI=1.05-2.18), and with daytime napping ⩾30min in men (HR 1.28: 95% CI, 1.00-1.64). Mechanisms for these differences are unknown.

Epidemiological study of sleep habits among four-and-a-half-year-old children in Japan

To date, only limited epidemiological data on the sleep habits of young children in Japan have been available. This study used representative samples to examine the sleep habits of four-and-a-half-year-old children in Japan. We used data from a nationwide cross-sectional survey. A member of each subject's family was asked to complete the questionnaire. The questionnaire included personal characteristics, sleep habits, and lifestyle. The data for 39,813 subject children (collection rate: 74.3%) were analyzed. The mean value of total sleep duration, night-time sleep duration, and daytime napping duration was 10 h 40 min 30 s, 9 h 53 min 0 s, and 46 min 24 s, respectively. The prevalence of daytime napping was 45.8%. Those whose total sleep duration was less than 10h accounted for 13.7% of the sample. The factors associated with high odds ratios for shorter total sleep duration were: living in a less populated area, long hours spent watching television, longer maternal work hours, and attending preschool. In attempting to devise ways of improving the sleep habits of young children, the lifestyles of both the children and their parents must be considered.

Duration of Sleep Inertia after Napping during Simulated Night Work and in Extended Operations

Due to the mixed findings of previous studies, it is still difficult to provide guidance on how to best manage sleep inertia after waking from naps in operational settings. One of the few factors that can be manipulated is the duration of the nap opportunity. The aim of the present study was to investigate the magnitude and time course of sleep inertia after waking from short (20-, 40- or 60-min) naps during simulated night work and extended operations. In addition, the effect of sleep stage on awakening and duration of slow wave sleep (SWS) on sleep inertia was assessed. Two within-subject protocols were conducted in a controlled laboratory setting. Twenty-four healthy young men (Protocol 1: n = 12, mean age = 25.1 yrs; Protocol 2: n = 12, mean age = 23.2 yrs) were provided with nap opportunities of 20-, 40-, and 60-min (and a control condition of no nap) ending at 02:00 h after ∼20 h of wakefulness (Protocol 1 [P1]: simulated night work) or ending at 12:00 h after ∼30 h of wakefulness (Protocol 2 [P2]: simulated extended operations). A 6-min test battery, including the Karolinska Sleepiness Scale (KSS) and the 4-min 2-Back Working Memory Task (WMT), was repeated every 15 min the first hour after waking. Nap sleep was recorded polysomnographically, and in all nap opportunities sleep onset latency was short and sleep efficiency high. Mixed-model analyses of variance (ANOVA) for repeated measures were calculated and included the factors time (time post-nap), nap opportunity (duration of nap provided), order (order in which the four protocols were completed), and the interaction of these terms. Results showed no test x nap opportunity effect (i.e., no effect of sleep inertia) on KSS. However, WMT performance was impaired (slower reaction time, fewer correct responses, and increased omissions) on the first test post-nap, primarily after a 40- or 60-min nap. In P2 only, performance improvement was evident 45 min post-awakening for naps of 40 min or more. In ANOVAs where sleep stage on awakening was included, the test x nap opportunity interaction was significant, but differences were between wake and non-REM Stage 1/Stage 2 or wake and SWS. A further series of ANOVAs showed no effect of the duration of SWS on sleep inertia. The results of this study demonstrate that no more than 15 min is required for performance decrements due to sleep inertia to dissipate after nap opportunities of 60 min or less, but subjective sleepiness is not a reliable indicator of this effect. Under conditions where sleep is short, these findings also suggest that SWS, per se, does not contribute to more severe sleep inertia. When wakefulness is extended and napping occurs at midday (i.e., P2), nap opportunities of 40- and 60-min have the advantage over shorter duration sleep periods, as they result in performance benefits ∼45 min after waking.

Investigating the biographic, social and temperamental correlates of young infants’ sleeping, crying and feeding routines

The aim of this study was to investigate the effect of intrinsic and extrinsic factors on feeding, sleeping and crying routines in infants aged between 4 and 10 weeks. Seventy-nine child–parent dyads from the North East of England participated in this cross-sectional study. Data on infant feeding, sleeping and crying routines was collected by parental diaries for a minimum of three days over the period of a week. Biographic data including age, birth-order, and sex and feeding method was collected by questionnaire and temperament was assessed using the Early Infancy Temperament Questionnaire. First-born infants were found to have longer feed duration and shorter nap and total sleep durations than subsequent infants. In addition, more positive temperament ratings tend to be related to greater total sleep duration. Breast-feeding and sex were related to more frequent waking and breast-feeding associated with more frequent feeding episodes. Age was associated with cry frequency. None of the independent variables used in the current analyses were related to infant cry duration. The results support previous findings but add to the current literature by showing that temperament and parity also have an effect on infant routines.