Uncertain call likelihood negatively affects sleep and next-day cognitive performance while on-call in a laboratory environment

ABSTRACT

On-call working arrangements are employed in a number of industries to manage unpredictable events, and often involve tasks that are safety- or time-critical. This study investigated the effects of call likelihood during an overnight on-call shift on self-reported pre-bed anxiety, sleep and next-day cognitive performance. A four-night laboratory-based protocol was employed, with an adaptation, a control and two counterbalanced on-call nights. On one on-call night, participants were instructed that they would definitely be called during the night, while on the other on-call night they were told they may be called. The State-Trait Anxiety Inventory form x-1 was used to investigate pre-bed anxiety, and sleep was assessed using polysomnography and power spectral analysis of the sleep electroencephalographic analysis. Cognitive performance was assessed four times daily using a 10-min psychomotor vigilance task. Participants felt more anxious before bed when they were definitely going to be called, compared with the control and maybe conditions. Conversely, participants experienced significantly less non-rapid eye movement and stage two sleep and poorer cognitive performance when told they may be called. Further, participants had significantly more rapid eye movement sleep in the maybe condition, which may be an adaptive response to the stress associated with this on-call condition. It appears that self-reported anxiety may not be linked with sleep outcomes while on-call. However, this research indicates that it is important to take call likelihood into consideration when constructing rosters and risk-management systems for on-call workers.     

The effect of osteoporosis on self-report sleep quality in postmenopausal women

We aimed to show the effect of osteoporosis on sleep quality in 59 postmenopausal women. The participants’ bone-mineral density levels were measured by dual-energy X-ray absorptiometry (DEXA). According to their DEXA results, participants were divided into two groups as osteoporotics and controls. The Pittsburgh Sleep Quality Index (PSQI) was used to evaluate sleep quality. Fourteen osteoporotic women (43.8%) and four controls (14.8%) were “poor” sleepers (p < 0.05). Postmeno-pausal women with osteoporosis scored greater on the “sleep latency” and “sleep duration” components of PSQI than controls. According to the findings of our study, osteoporosis is a risk factor for poor sleep quality in postmenopausal women.

     

Can stress act as a sleep inertia countermeasure when on-call?

The nature of on-call work is such that workers can be called and required to respond immediately after being woken. However, due to sleep inertia, impaired performance immediately upon waking is typical. We investigated the impact of a preceding stressor (an alarm/mobilisation procedure) on sleepiness and performance upon waking. Healthy, adult males (n = 16) attended the sleep laboratory for four consecutive nights which included two, counterbalanced on-call sleeps where participants were woken at 04:00 h by (a) an alarm/mobilisation procedure (Alarm) or (b) gently by a researcher (Control). Following waking was a 2-h testing session comprising the repeated administration of the Karolinska Sleepiness Scale (KSS) and 5-min Psychomotor Vigilance Task (PVT). Results from within-subjects analysis of variance in both the Control and Alarm conditions showed that for subjective sleepiness (KSS) there was a significant fixed effect of time (p = 0.012), with participants becoming less sleepy as time post-wake increased. In terms of PVT performance outcomes, in neither the Alarm or Control conditions were there measurable signs of sleep inertia with performance remaining stable across the 2-h testing period. Based on previous research measuring impact of sleep inertia when woken near the circadian nadir, performance findings in particular were unexpected. We propose that stress caused by study procedures (i.e. finger pricks using lancets) unrelated to the simulated wake-up protocols may have countered any impact of sleep inertia on performance.     

WORK HOURS AND SLEEP/WAKE BEHAVIOR OF AUSTRALIAN HOSPITAL DOCTORS

The objective of the study was to describe the work and sleep patterns of doctors working in Australian hospitals. Specifically, the aim was to examine the influence of work-related factors, such as hospital type, seniority, and specialty on work hours and their impact on sleep. A total of 635 work periods from 78 doctors were analyzed together with associated sleep history. Work and sleep diary information was validated against an objective measure of sleep/wake activity to provide the first comprehensive database linking work and sleep for individual hospital doctors in Australia. Doctors in large and small facilities had fewer days without work than those doctors working in medium-sized facilities. There were no significant differences in the total hours worked across these three categories of seniority; however, mid-career and senior doctors worked more overnight and weekend on-call periods than junior doctors. With respect to sleep, although higher work hours were related to less sleep, short sleeps (< 5 h in the 24 h prior to starting work) were observed at all levels of prior work history (including no work). In this population of Australian hospital doctors, total hours worked do impact sleep, but the pattern of work, together with other nonwork factors are also important mediators. (Author correspondence: sally.ferguson@unisa.edu.au)     

On-Call Duty Effects on Sleep-State Physiological Stability in Male Medical Interns

Background

On-call duty among medical interns is characterized by sleep deprivation and stressful working conditions, both of which alter cardiac autonomic modulation. We hypothesized that sleep stability decreased in medical interns during on-call duty. We used cardiopulmonary-coupling (CPC) analysis to test our hypothesis.

Methods

We used electrocardiogram (ECG)-based CPC analysis to quantify physiological parameters of sleep stability in 13 medical interns during on-call and on-call duty-free periods. There were ten 33.5-h on-call duty shifts per month for interns, each followed by 2 on-call duty-free days, over 3 months. Measurements during sleep were collected before, during, and after an on-call shift. Measurements were repeated 3 months later during an on-call duty-free period.

Results

The medical interns had significantly reduced stable sleep, and displayed increased latency to the first epoch of stable sleep during the on-call night shift, compared to the pre-call and on-call duty-free nights. Interns also had significantly increased rapid-eye-movement (REM) sleep during the on-call night shift, compared to the pre-call and on-call duty-free nights.

Conclusion

Medical interns suffer disrupted sleep stability and continuity during on-call night shifts. The ECG-based CPC analysis provides a straightforward means to quantify sleep quality and stability in medical staff performing shift work under stressful conditions.     

Eveningness associates with smoking and sleep problems among pregnant women

Sleep problems during pregnancy impair maternal health and increase the risk for adverse pregnancy outcome. The circadian preference toward eveningness has been associated with sleep problems in previous studies. Here, we studied whether evening-type women had more sleep problems during their pregnancy, as compared with other chronotypes, in a sample consisting of 1653 pregnant women from the Finnish CHILD-SLEEP Birth Cohort. Chronotype was assessed with a shortened version of the morningness–eveningness questionnaire. Pregnant evening-type women reported more sleep problems, including troubles of falling asleep (OR = 3.4, p < 0.0001), poor sleep quality (OR = 2.9, p < 0.01) and daily tiredness (OR = 3.2, p < 0.0001) than the morning-type women, even after controlling for sleep duration and sleep deprivation. They had higher scores on Epworth Sleepiness Scale (p < 0.05), Basic Nordic Sleep Questionnaire (p < 0.0001) and Global Seasonality Score (p < 0.01) and were also more often smokers, also during pregnancy (p < 0.001) and reported poorer general health (p < 0.001) than the morning-type women. They also reported having had more sleep problems during their childhood (OR = 1.5, p < 0.05) and adolescence (OR = 2.0, p < 0.001) than the morning-type women. Our results indicate that eveningness is associated with more sleep problems and unhealthy life habits during pregnancy.     

Impacts of intensive dairy production on smallholder farm women in coastal Kenya

Welfare impacts of an intensive dairy technology package on women and their families are investigated on 32 smallholder crop-livestock farms in the sub-humid zone off Kilifi District, Coast Province, Kenya. Farms were stratified according to male or female extension contact. A female enumerator interviewed the wife or female head of household on each farm regarding her present and past household responsibilities and the affects of the intensive dairy enterprise on these duties and upon the welfare of the household. On three-quarters of the male contact farms, dairy operators were women. Across all farms, women performed half of all dairy-related activities, but only on female contact farms did income from the dairy enterprise accrue to women in proportion to their labor input. The equitable return of benefits to labor corresponded with better dairy unit performance on female contact farms, where women also indicated greater access to and autonomy over household resources and decision-making. Irrespective of extension contact, there was broad consensus among the women interviewed that intensive dairying has led to improved household welfare, primarily through increased household income and milk consumption. There was also wide agreement, however, that these gains have been achieved at the expense of more work for women. Women on female contact farms were observed spending dairy income on food for the household and childrens' schooling more often than their counterparts on male contact farms. Based on these and other findings, the study concludes that gender of the extension contact, dairy operator and farm owner were determinants of the intra-household impacts of intensive dairying on the smallholder farms in this study. Recommendations for design and delivery of livestock technologies for crop-based farming systems, with special emphasis on how to minimize negative impact on vulnerable household members, are inferred from study findings.Formerly International Livestock Research Institute, P.O. Box 30709, Nairobi, Kenya.     

The association of a distinct plasma proteomic profile with the cervical high-grade squamous intraepithelial lesion of Uyghur women: a 2D liquid-phase chromatography/mass spectrometry study

Objective: To identify plasma protein biomarkers of cervical high-grade squamous intraepithelial lesion (HSIL) of Uyghur women by proteomics approach.

Methods: Plasma protein samples of Uyghur women with HSIL and chronic cervicitis were analyzed with 2D HPLC followed by detection of target proteins with Linear Trap Quadrupole Mass Spectrometer (LTQ MS/MS).

Results: We detected three upregulated and one downregulated protein peaks representing protein constituents distinguishing HSIL from controls by 2D HPLC, identified 31 target proteins by LTQ MS/MS. Further confirmed analysis with online software IPA^® 8.7 and ELISA assay showed APOA1 and mTOR as potential biomarkers.

Conclusions: A distinct plasma proteomic profile may be associated with HSIL of Uyghur women.     

Oxidative stress and antioxidant defenses in pregnant women

Abstract

Objectives

Oxidative stress (OS) is defined as an imbalance in the production of reactive oxygen species and the capacity of antioxidant defenses. The objective of this work was to investigate OS and antioxidant capacity in pregnant women.

Methods

Parameters of the oxidative status and antioxidant capacity in serum and whole blood were evaluated in thirty-nine women with normal pregnancy.

Results

The assessment of antioxidants indicated an increase in superoxide dismutase and catalase activities (P < 0.05 and P < 0.01) and a decrease in ascorbic acid levels and the total content of sulfhydryl (P < 0.05 and P < 0.001). Additionally, when the pro-oxidant system was investigated we found an increase (P < 0.01) in malondialdehyde and no significant change (P > 0.05) in protein carbonylation.

Discussion

This study demonstrates that there is a change in the pro-oxidant and antioxidant defenses associated with body and circulation changes that are inherent to the pregnancy process.     

New Zealanders working non-standard hours also have greater exposure to other workplace hazards

Exposure to workplace hazards, such as dust, solvents, and fumes, has the potential to adversely affect the health of people. However, the effects of workplace hazards on health may differ when exposure occurs at different times in the circadian cycle, and among people who work longer hours or who do not obtain adequate sleep. The aim of the present study was to document exposures to workplace hazards across a national sample of New Zealanders, comparing people who work a standard 08:00 ?17:00 h Monday-to-Friday working week (Std hours) and those who do not (N-Std hours). New Zealanders (n = 10 000) aged 20–64 yrs were randomly selected from the Electoral Roll to take part in a nationwide survey of workplace exposures. Telephone interviews were conducted between 2004 and 2006, using a six-part questionnaire addressing demographics, detailed information on the current or most recent job (including exposures to a range of workplace hazards), sleep, sleepiness, and health status. N-Std hours were categorised on the basis of: being required to start work prior to 07:00 h or finish work after 21:00 h and/or; having a regular on-call commitment (at least once per week) and/or; working rotating shifts and/or; working night shift(s) in the last month. The response rate was 37% (n = 3003), with 22.2% of participants (n = 656) categorised as working N-Std hours. Industry sectors with the highest numbers of participants working N-Std hours were manufacturing, health and community services, and agriculture, fishing, and forestry. Response rate was 37% (n = 3003) with 22.2% (n = 656) categorised as working N-Std hours. Participants working N-Std hours were more likely to be exposed to all identified hazards, including multiple hazards (OR = 2.45, 95% CI = 2.01–3.0) compared to those working Std hours. Participants working N-Std hours were also more likely to report ‘never/rarely’ getting enough sleep (OR = 1.38, 95% CI = 1.15–1.65), ‘never/rarely’ waking refreshed (OR = 1.23, 95% CI = 1.04–1.47), and excessive sleepiness (OR = 1.77, 95% CI = 1.29–2.42). New Zealanders working N-Std hours are more likely to be exposed to hazards in the workplace, to be exposed to multiple hazards, and to report inadequate sleep and excessive sleepiness than their colleagues working a standard 08:00?17:00 h Monday-to-Friday working week. More research is needed on the effects of exposure to hazardous substances outside the usual waking day, on the effects of exposure to multiple hazards, and on the combination of hazard exposure and sleep restriction as a result of shift work.     

Impact of single anaerobic exercise on delayed activation of endothelial xanthine oxidase in men and women

Objectives: The aim of the study was to evaluate the activity of xanthine oxidase (XO) in the blood of men and women during the first hour following a single anaerobic exercise (AN-EX), and after 24 hours of recovery, and to determine whether the changes in XO activity in the blood after AN-EX are dependent on anaerobic performance.

Methods: Ten men and ten women performed a single AN-EX. Blood was collected before and five times after completion of the AN-EX. The activity of XO was determined.

Results: In both groups, a significant (P?P?Discussion: In the first hour after the single AN-EX, XO activity in the blood of women and men did not change, but after 24 hours of recovery, it was significantly higher compared to baseline levels in both sexes. Single AN-EX causes a smaller increase in XO activity in people with higher anaerobic performance.     

First outbreak reported caused by Erysipelothrix species strain 2 in turkeys from poultry-producing farms in Brazil

Purpose

The aims of this study were to report the first isolation of Erysipelothrix sp. strain 2 (ES2) associated with clinical signs of diseases as well as mortality in turkeys and identify the antimicrobial resistance of the isolates.

Methods

We evaluated 118 farms for bacteriological analysis and TaqMan real-time PCR to identify the microorganism in different organs. After this, we made the epidemiological analysis between the positive flocks and the mortality mean. We performed the sequencing of the 16S rRNA region and the assessment of antimicrobial resistance.

Results

We have identified 18 (15.25%) as ES2-positive flocks, without any other species from the same genus being found. After analysing the organ samples, we found liver as the organ of choice for the isolation of the ES2. The sequencing of 16S rRNA region of ES2 identified high homology with E. tonsillarum and E. rhusiopathiae, suggesting that it is not the best-suited target to identify this species. We have found a positive association between isolation of the bacteria in organs and flocks’ mortality. Positive flocks had a mortality mean rate of 6.87%, which is significantly greater than 3.76% in negative flocks. Ill turkeys had gross lesions of generalized septicaemia. The bacterial isolates showed high resistance to fosfomycin and trimethoprim/sulfamethoxazole and sensibility to norfloxacin, amoxicillin and lincomycin/spectinomycin.

Conclusion

This is the first study in the world that addressed ES2 as the causative agent of erysipelas in turkey.

     

Uric acid correlates to oxidation and inflammation in opposite directions in women

Abstract

Objective: To evaluate the association of uric acid (UA) levels with a panel of markers of oxidative stress and inflammation.

Methods: Plasma UA levels, along with a panel of oxidative stress and inflammatory markers, were measured in 755 Chinese women.

Results: Plasma UA levels were inversely associated with urinary levels of the oxidative stress marker F₂-isoprostanes and positively correlated to levels of inflammatory markers, such as C-reactive protein and some proinflammatory cytokines (tumor necrosis factor-α and interleukin-6) in blood as well as prostaglandin E₂ metabolites in urine.

Conclusions: Plasma UA levels correlate to oxidation and inflammation biomarkers in opposite directions in women.     

Time of day effect on balance performance,functional capacities and risk of fall in women with rheumatoid arthritis

ABSTRACT

Objective: This study explored the time of day effect of balance performance, functional capacities and risk of fall in three different times in patients with rheumatoid arthritis (RA) and the association between these variations and those of RA symptoms.

Methods: A “discontinual” protocol, composed of three test sessions, carried out at 6 am, 2 pm and 10 pm was set up, in order to investigate the time of day effect of balance performance, functional capacities, risk of fall, stiffness, range of motion, swollen and painful joints in women with RA.

Results: Time Up and Go Test (TUGT), Functional Reach Test (FRT) and tinetti test scores were significantly higher (p < .01) at 6 am and at 10 pm compared to 2 pm. Stiffness, range of motion, swollen and painful joints values were significantly higher (p < .01) at 6 am and at 10 pm compared to 2 pm. A significant difference was observed on the stiffness, range of motion and swollen joints values between 6 am and 10 pm that were higher at 6 am (p < .05).

Using Pearson’s coefficient, correlations were found between RA symptom values; and TUGT, FRT and Tinetti test scores.

Conclusion: Results showed a time of day effect of balance performance, functional capacities and risk of falls in women with RA. This variation indicates an alteration of performance at 6 am and 10 pm. Fluctuations of stiffness, limited range of motion, swollen and painful joints noted are concomitant to those of balance performance, functional capacities, and risk of fall.

Abbreviations: RA: rheumatoid arthritis; H&O questionnaire: Horne and Ostberg questionnaire; PSQI: Pittsburgh sleep quality index; HAQ: health assessment questionnaire; SF-36: the short form-36; WOMAC: Western Ontario and McMaster Universities Osteoarthritis Index; TUGT: Time Up and Go Test; FRT: Functional Reach Test     

Effect of maximal-intensity exercise on systemic nitro-oxidative stress in men and women

Objectives: The aim of this study was to test the hypotheses: (1) there is a negative correlation between protein and lipid oxidative damage following maximal-intensity exercise, and oxygen uptake and work intensity (%VO_2max) at the respiratory compensation point (RCP) in women and men; (2) nitro-oxidative stress following maximal-intensity exercise results from the intensification of anaerobic processes and muscle fibre micro-damage.

Methods: Study participants comprised 20 women (21.34±1.57 years) and 20 men (21.97±1.41 years) who performed a treadmill incremental test (IT); VO_2max: 45.08?±?0.91 and 57.38?±?1.22?mL?kg^?1?min^?1 for women and men, respectively. The oxidized low-density lipoprotein (ox-LDL), 3-nitrotyrosine (3-NT) concentration and creatine kinase (CK) as well as lactate dehydrogenase (LDH) activity were measured in the blood serum, and total antioxidative capacity (TAC) and lactate concentration (Lac) were determined in blood plasma before and after IT.

Results: After the IT, increases in ox-LDL, 3-NT, CK, and LDH were seen in both groups (P?P?P?Conclusions: The gain of ox-LDL and 3-NT following maximal-intensity exercise is independent of VO_2max, oxygen consumption and exercise intensity at RCP. This increase of ox-LDL and 3-NT is indicative of similar lipid and protein damage in women and men. A significant increase in TAC in women following maximal-intensity exercise is the result of muscle fibre micro-injuries.     

Sleep Patterns of Day-Working,Evening High-Schooled Adolescents of São Paulo,Brazil

Children who grow up in developing countries of the world must work to help financially support their families, and they must also attend school. We investigated the impact of work on the sleep of working vs. nonworking high school students. Twenty-seven São Paulo, Brazil, public high school students (eight male and eight female working students plus six nonworking female and five nonworking male students) 14–18 yrs of age who attended school Monday–Friday between 19:00 to 22:30 h participated. A comprehensive questionnaire about work and living conditions, health status, and diseases and their symptoms was also answered. The activity level and rest pattern (sleep at night and napping during the day) were continuously assessed by wrist actigraphy (Ambulatory Monitoring, USA). The main variables were analyzed by a two-factor ANOVA with application of the Tukey HSD test for multiple comparisons, and the length of sleep during weekdays vs. weekends was compared by Student t-test. Working students went to sleep earlier weekends [F_(1,23) = 6.1; p = 0.02] and woke up earlier work days than nonworking students [F_(1,23) = 17.3; p = 0.001]. The length of nighttime sleep during weekdays was shorter among all the working [F_(1,23) = 16.7; p < 0.001] than all the nonworking students. The sleep duration of boys was shorter than of girls during weekends [F_(1,23) = 10.8; p < 0.001]. During weekdays, the duration of napping by working and nonworking male students was shorter than nonworking female students. During weekdays, working girls took the shortest naps [F_(1,23) = 5.6; p = 0.03]. The most commonly reported sleep complaint during weekdays was difficulty waking up in the morning [F_(1,23) = 6.5; p = 0.02]. During weekdays, the self-perceived sleep quality of working students was worse than nonworking students [F_(1,23) = 6.2; p = 0.02]. The findings of this study show that work has negative effects on the sleep of adolescents, with the possible build-up of a chronic sleep debt with potential consequent impact on quality of life and school learning.     

Leptin to high-molecular-weight adiponectin ratio is independently correlated with carotid intima-media thickness in men,but not in women

Background: The leptin:adiponectin ratio (L:A ratio) is an independent predictor of carotid intima-media thickness (CIMT).

Objective: To evaluate whether the leptin:high-molecular-weight adiponectin ratio (L:HA ratio) is associated with CIMT in the general population.

Methods: We investigated the relationship between the L:HA ratio and CIMT in 233 Japanese study participants (106 men and 127 women).

Results: After adjustment for confounding factors, CIMT was significantly correlated with the log L:HA ratio (β?=?0.11, p?=?0.014) in men, whereas no correlation was observed in women (β?=?0.01, p?=?0.50).

Conclusion: The L:HA ratio is closely correlated with CIMT in men, but not in women.     

Subjective and objective sleep among air ambulance personnel

ABSTRACT

The present study aimed to investigate the effects of shift work on sleep among pilots and Helicopter Emergency Medical Service crew members (HCM) in the Norwegian Air Ambulance. Sleep was assessed by diaries and actigraphy during a workweek (24 h duty for 7 consecutive days) in the winter season and a workweek during the summer season in pilots and HCM (N = 50). Additionally, differences in sleep were studied between the week before work, the workweek, and the week after work in both seasons. Results indicated that bedtime was later (p <.001) and time spent in bed (p <.05) was shorter during the summer, compared to the winter, season. The workers delayed the sleep period in the workweek, compared to the week before (winter: p <.001, summer: p <.001) and the week after (winter: p <.05-.001, summer: p <.001). They spent more time in bed during the workweek, compared to the week before (winter: p <.001, summer: p <.01) and after (winter: p <.001, summer: p =.37). Further, the workers had longer wake after sleep onset during the workweek, compared to the week before (winter: p <.001, summer: p <.01) and the week after (winter: p <.01, summer: p <.01). Finally, the workers had lower sleep efficiency during the workweek recorded by actigraphy compared to the week before (winter: p <.01, summer: p <.001) and the week after (winter: p <.01, summer: p <.001). According to the sleep diaries the total sleep time was 7:17 h in the winter and 7:03 h in the summer season. Overall, the sleep was somewhat affected during the workweek, with delayed sleep period, longer wake after sleep onset, and lower sleep efficiency compared to when off work. However, the workers spent more time in bed during the workweek compared to the weeks off, and they obtained over 7 h of sleep in both workweeks. Our findings suggest that the pilots and the HCM sleep well during the workweek, although it affected their sleep to some extent.     

Biological monitoring of exposure to low concentrations of benzene in workers at a metallurgical coke production plant: new insights into S-phenylmercapturic acid and urinary benzene

Context: Urinary S-phenylmercapturic acid (SPMA) and benzene (U-Ben) are usually measured at the end of the work shift (ES), although their kinetic of elimination is not clearly known.

Objective: To investigate SPMA and U-Ben elimination 16?h after the ES, in 93 coke production workers exposed to low benzene concentrations.

Materials and methods: Airborne benzene (A-Ben) was measured by passive samplings, while SPMA, U-Ben, methyl-tert-butyl ether (U-MTBE), cotinine (U-Cot) and creatinine were determined on urine samples collected at ES and before the beginning of the next work shift (next BS).

Results: Median A-Ben concentrations were 17.2?µg/m³ in the personal and 34.7?µg/m³ in the stationary samplings. SPMA was always detectable, whereas U-Ben was below the limit of quantification in 26.7% of the ES and 35.6% of the next BS samples, and U-MTBE in more than the 80.0% of the samples. At both the sampling times, SPMA and U-Ben showed a positive dependence on personal A-Ben, as well as on creatinine and U-Cot values.

Discussion and conclusion: SPMA and U-Ben at the next BS were dependent on the exposure to low benzene concentrations suffered in the previous work shift, prompting a reconsideration of the urine sampling time recommended by the American Conference Governmental Industrial Hygienists (ACGIH).     

Sleep habits of Iranian pre-school children in an urban area: Late sleeping and sleep debt in children

Using BEARS (Bedtime problems, Excessive sleepiness, Awakenings during the night, Regularity of sleep, Snoring), and CSHQ (Children’s Sleep Habits Questionnaires) screening tools with 224 participants revealed that Iranian children have shorter night sleep duration than expected (9.54 vs 12 h) for their age group. Earlier sleepers had longer night sleep duration (10:36 ± 1:12; 9:12 ± 1:06 h, P > 0.001), and total daily sleep time (11:36 ± 1:42; 10:36 ± 1:30 h, P = 0.005) than late sleepers. A majority (85%) of naptakers had sleep bedtime of 22:00 or later. The poor sleep quality of Iranian preschool children is probably due to cultural characteristics, climate differences, or harmful sleep habits.