Trends of self-reported sleep duration in Korean Adults: results from the Korea National Health and Nutrition Examination Survey 2007-2015

The role of education attainment on 24-hour movement behavior in emerging adults: evidence from a population-based study

Purpose

The purpose of this study was to explore the relationship between education level and health behavior including sleep, work activity, exercise activity, and sedentary behavior among emerging adults.

Methods

This study utilized data from the National Health and Nutrition Examination Survey (NHANES) collected between 2007 and 2018. The study sample included 4,484 emerging adults aged 18-25 years and the weighted participants were 30,057,813. Weighted multivariable regression analysis was performed to investigate the association between education level and the aforementioned health behavior, adjusting for age, gender, race/ethnicity, marital status, poverty-income ratio, BMI, smoking, and alcohol drinking status.

Results

This study revealed that higher education level was associated with shorter sleep duration [Fully adjusted model, β (95% CI): -0.588 (-0.929, -0.246), p < 0.001]. Additionally, those with higher education levels were more likely to allocate time in sedentary behavior [β (95% CI): 90.162 (41.087, 139.238), p < 0.001]. Moreover, higher education level was related to less work activity [β (95% CI): -806.991 (-1,500.280, -113.703), p = 0.023] and more exercise activity time [β (95% CI): 118.196 (-21.992, 258.385), p = 0.097]. Subgroup analysis further verified this trend and detected that males with higher education level tended to participate in less work activity [β (95% CI): -1,139.972 (-2,136.707, -143.237), p = 0.026] while females with higher education level tended to engage in more exercise activity [Fully adjusted model, β (95% CI): 141.709 (45.468, 237.950), p = 0.004].

Conclusion

This study highlighted the importance of education level as a significant factor in promoting healthy behavior among emerging adults. The findings underscored the need for the Ministry of Education to prioritize educating this demographic about the significance of maintaining adequate sleep patterns and reducing sedentary habits. Encouraging them to allocate more time for work and physical activities can significantly contribute to their overall wellbeing and success, ultimately fostering a healthier next generation.

A real-time, personalized sleep intervention using mathematical modeling and wearable devices

The prevalence of artificial light exposure has enabled us to be active any time of the day or night, leading to the need for high alertness outside of traditional daytime hours. To address this need, we developed a personalized sleep intervention framework that analyzes real-world sleep-wake patterns obtained from wearable devices to maximize alertness during specific target periods. Our framework utilizes a mathematical model that tracks the dynamic sleep pressure and circadian rhythm based on the user's sleep history. In this way, the model accurately predicts real-time alertness, even for shift workers with complex sleep and work schedules (N = 71, t = 13~21 days). This allowed us to discover a new sleep-wake pattern called the adaptive circadian split sleep, which incorporates a main sleep period and a late nap to enable high alertness during both work and non-work periods of shift workers. We further developed a mobile application that integrates this framework to recommend practical, personalized sleep schedules for individual users to maximize their alertness during a targeted activity time based on their desired sleep onset and available sleep duration. This can reduce the risk of errors for those who require high alertness during nontraditional activity times and improve the health and quality of life for those leading shift work-like lifestyles.

The influence of sleep on job satisfaction: examining a serial mediation model of psychological capital and burnout

Introduction

This study draws on the conservation of resources theory to investigate whether the loss of sleep can trigger the loss of additional resources that are necessary for work.

Methods

Using cross-sectional design of 322 call center employees working at a government-owned public bank in South Korea, we test the study hypotheses using regression and bootstrapping indirect effects analyses.

Results

The results of analyses show that insufficient sleep increases employee burnout and that psychological capital mediates this relationship. We also find that insufficient sleep decreases job satisfaction via a serial mediation model such that insufficient sleep reduces psychological capital, which in turn increases burnout, and ultimately results in lower job satisfaction.

Discussion

The findings reinforce the previous assessment that although sleep is a non-work factor, its impact spills over to the workplace. Theoretically, this study goes beyond direct effect to uncover the underlying or mediating mechanisms that account for the impact of the sleep-burnout relationship and the sleep-job satisfaction relationship. For managers, the results highlight the significance of sleep to employees' overall health and well-being and thus underscore the need to foster a work culture that recognizes and prioritizes employee sleep needs.

The Effect of Aerobic Exercise on Variation of Oxidative Stress, hs-CRP and Cortisol Induced by Sleep Deficiency

The aim of this study was to investigate the impact of sleep deficiency (SD) on oxidative stress, hs-CRP and cortisol levels and to examine the effects of different intensities of aerobic exercise on these parameters under SD conditions. Thirty-two healthy male university students participated in the study and underwent both normal sleep (NS, 8 h of sleep per night for 3 consecutive days) and SD (4 h of sleep per night for 3 consecutive days). After the SD period, the participants performed treatment for 30 min according to their assigned group [sleep supplement after SD (SSD), low-intensity aerobic exercise after SD (LES), moderate-intensity aerobic exercise after SD (MES), high-intensity aerobic exercise after SD (HES)]. Sleep-related factors were measured at NS and SD, while oxidative stress, hs-CRP and cortisol levels were measured at NS, SD and immediately after treatment by group (AT). The results showed that actual total sleep time (ATST) was significantly reduced during SD compared to NS (p < 0.001), while the visual analogue scale (VAS) and Epworth sleepiness scale (ESS) were significantly increased during SD compared to NS (p < 0.001). The difference in reactive oxygen metabolites (d-ROMs) and cortisol levels showed a significant interaction effect (p < 0.01, p < 0.001, respectively), with LES showing a decrease in d-ROMs and cortisol levels compared to SD (p < 0.05). Similarly, SSD showed a decrease in cortisol levels compared to SD (p < 0.05), while HES led to a significant increase in d-ROMs and cortisol levels compared to SD (p < 0.05). Biological antioxidant potential (BAP) and hs-CRP did not show any significant effect (p > 0.05). These results suggest that LES is the most effective exercise intensity for mitigating the negative effects of SD.

Long Sleep Duration and Dissatisfaction with Sleep Quality Are Associated with Ischemic Stroke in Young Patients

INTRODUCTION

Suboptimal sleep duration and poor sleep quality have been proposed to increase stroke risk. However, their significance in young ischemic stroke is unclear. We aimed to investigate the importance of sleep duration and quality on young ischemic stroke patients.

METHODS

A multicenter matched case-control study was performed to evaluate under-recognized risk factors in young (<45 years) ischemic stroke patients in 8 tertiary hospitals in Korea. A total of 225 patients and 225 age- and sex-matched controls were enrolled in the same period. Detailed information about patients' demographics, socioeconomic state, and traditional and nontraditional risk factors including sleep-related factors were obtained using structured questionnaires. Risk of ischemic stroke was estimated using conditional logistic regression analysis.

RESULTS

Although average sleep duration was similar in patients and controls, patients were more likely to have long (≥9 h) or extremely short (<5 h) sleep durations. In addition, the proportion of subjects with dissatisfaction with sleep quality was higher in patients than controls (66.2 vs. 49.3%, p < 0.001). In multivariable conditional logistic regression analysis, long sleep duration (OR: 11.076, 95% CI: 1.819-67.446, p = 0.009) and dissatisfaction with sleep quality (OR: 2.116, 95% CI: 1.168-3.833, p = 0.013) were independently associated with risk of ischemic stroke.

CONCLUSIONS

Long sleep duration and dissatisfaction with sleep quality may be associated with increased risk of ischemic stroke in young adults. Improving sleep habit or quality could be important for reducing the risk of ischemic stroke.

Trends in sleep duration in Korea: The Korean time use survey

OBJECTIVES

An accurate assessment of sleep duration is important in that it can be one of the indicators of a country's overall health and well-being. The global trend in sleep duration is controversial according to study types. We investigated trends in sleep duration in South Korea with a time diary method.

METHODS

Data from the Korean Time Use Survey (KTUS) in 2004, 2009, 2014, and 2019, were analyzed. The KTUS is a nationwide, cross-sectional survey that measures daily time use patterns of individuals and has been performed every five years by Statistics Korea. For this survey, all participants were asked to record their activities for 2 continuous days in 10-min intervals.

RESULTS

Among the 168,682 people who completed the survey in 2004 through 2019, the final analytical sample consisted of 91,998 individuals. Over 15 years, the sleep duration of the Korean population increased from 411.1 min (SD 22.5) in 2004 to 434.5 min (SD 26.1) in 2019 (p for trend <0.001). This increase was observed for all age groups. Over the study period, while bedtime showed no significant change, wake time was generally delayed for all age groups. The increase in sleep duration in the Korean population was largely due to catch-up sleep on Saturdays, which was substantially prolonged with belated wake times.

CONCLUSION

Our nationwide time use survey data showed that sleep duration in South Korea has increased over the past 15 years but still has room for improvement in terms of weekday sleep duration.

Validation of Fitbit Inspire 2TM Against Polysomnography in Adults Considering Adaptation for Use

PURPOSE

The commercialization of sleep activity tracking devices has made it possible to manage sleep quality at home. However, it is necessary to verify the reliability and accuracy of wearable devices through comparison with polysomnography (PSG), which is the standard for tracking sleep activity. This study aimed to monitor overall sleep activity using Fitbit Inspire 2™ (FBI2) and to evaluate its performance and effectiveness through PSG under the same conditions.

PATIENTS AND METHODS

We compared the FBI2 and PSG data of nine participants (four male and five female participants; average age, 39 years) without severe sleeping problems. The participants wore FBI2 continuously for 14 days, considering the period of adaptation to the device. FBI2 and PSG sleep data were compared using paired t-tests, Bland-Altman plots, and epoch-by-epoch analysis for 18 samples by pooling data from two replicates.

RESULTS

The average values for each sleep stage obtained from FBI2 and PSG showed significant differences in the total sleep time (TST), deep sleep, and rapid eye motion (REM). In the Bland-Altman analysis, TST (P = 0.02), deep sleep (P = 0.05), and REM (P = 0.03) were significantly overstated in FBI2 compared to PSG. In addition, time in bed, sleep efficiency, and wake after sleep onset were overestimated, while light sleep was underestimated. However, these differences were not statistically significant. FBI2 showed a high sensitivity (93.9%) and low specificity (13.1%), with an accuracy of 76%. The sensitivity and specificity of each sleep stage was 54.3% and 62.3%, respectively, for light sleep, 84.8% and 50.1%, respectively, for deep sleep, and 86.4% and 59.1%, respectively for REM sleep.

CONCLUSION

The use of FBI2 as an objective tool for measuring sleep in daily life can be considered appropriate. However, further research is warranted on its application in participants with sleep-wake problems.

[Influence of sleep and chrononutrition on hypertension and diabetes: a population-based study]

The objective is to evaluate the influence of sleep and chrononutrition on hypertension and diabetes in the adult population (18 years or older) in a municipality in Southern Brazil. This is a population-based cross-sectional study, developed in Criciúma, State of Santa Catarina, in 2019. The exposure variables were sleep duration and quality, and two of the main aspects of chrononutrition, the number of daily meals and the presence of breakfast. The outcomes studied were diabetes mellitus and systemic arterial hypertension. Crude and adjusted Poisson regression with robust variance was used to evaluate the associations between exposures and outcomes. For all analyses, the effect of the sample design was considered, and the significance level adopted was 5%. In total, 820 patients were evaluated. The prevalence of diabetes and hypertension was of 19.9% and 44.1%, respectively. Individuals with worse sleep quality had a higher prevalence of 33% for diabetes and 17% for hypertension, compared to those with good quality of sleep. Those who had four or more meals per day had a 16% lower prevalence of hypertension, when compared to those who had less than four meals. We concluded that the quality of sleep and the number of daily meals, a feeding behavior related to chrononutrition, were related to hypertension and diabetes. These results highlight the importance of public health actions that address new strategies for coping with these diseases focused on sleep quality and chrononutrition.

Association between Sleep Duration and Physical Fitness in Children Aged 3-6 Years: A Cross-Sectional Study from China

Aim: To explore associations between sleep duration and physical fitness (PF) of children aged 3−6 years. Methods: This study investigated the sleep duration and PF data of children aged 3−6 years by stratified random sampling. The restricted cubic spline model and binary logistic regression analysis were mainly used for the empirical analysis of the correlation effect between sleep duration and PF. The final data had a total of 21,857 children, of which 11,245 (51.45%) were boys and 10,612 (48.55%) were girls. Results: The PF level of the children in this study showed a relatively positive level (pass rate = 93.6%), and 19.7% of them had abnormal sleep duration; the results of the restricted cubic spline showed an inverted U-shaped association between the level of PF and the risk of abnormal sleep duration (X2 = 28.13, p < 0.0001). The results of logistic regression analysis showed that children with abnormal sleep duration were more likely to have a low PF, body morphology and motor ability levels at an OR (95% CI) of 1.077 (1.023−1.133), 1.077 (1.016−1.142) and 1.035 (1.08−1.062), respectively. The results of the bias correlation analysis showed varying degrees of correlation between sleep duration and various components of children’s PF. Conclusion: Insufficient or excessive amounts of sleep were significantly associated with PF in children, with abnormal sleep duration leading to reduced levels of PF and its components.

Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysis

OBJECTIVE

To determine the effect of Ashwagandha extract on sleep.

METHODS

A comprehensive search was conducted in CENTRAL, MEDLINE, SCOPUS, Google Scholars, World Health Organization Trials Portal, ClinicalTrials.gov, Clinical Trial Registry of India, and AYUSH Research Portal for all appropriate trials. Randomized controlled trials that examined the effect of Ashwagandha extract versus placebo on sleep in human participants 18 years old and above were considered. Two authors independently read all trials and independently extracted all relevant data. The primary outcomes were sleep quantity and sleep quality. The secondary outcomes were mental alertness on rising, anxiety level, and quality of life.

RESULTS

A total of five randomized controlled trials containing 400 participants were analyzed. Ashwagandha extract exhibited a small but significant effect on overall sleep (Standardized Mean Difference -0.59; 95% Confidence Interval -0.75 to -0.42; I2 =  62%). The effects on sleep were more prominent in the subgroup of adults diagnosed with insomnia, treatment dosage ≥600 mg/day, and treatment duration ≥8 weeks. Ashwagandha extract was also found to improve mental alertness on rising and anxiety level, but no significant effect on quality of life. No serious side effects were reported.

CONCLUSION

Ashwagandha extract appears to has a beneficial effect in improving sleep in adults. However, data on the serious adverse effects of Ashwagandha extract are limited, and more safety data would be needed to assess whether it would be safe for long-term use.

Association between exercise variations and depressive symptoms among precarious employees in South Korea

Research regarding the association between depression and exercise has been limited regarding precariously employed individuals. The current study investigated the association between exercise variations and depressive symptoms among precarious employees in South Korea. Data from the 2014, 2016, and 2018 Korea National Health and Nutrition Examination Survey (KNHANES) were analyzed. In total, 13,080 participants aged ≥ 19 years responded to the survey. The Korean version of the PHQ-9 was utilized in addition to questions assessing regular exercise. Precariously employed men engaging in two or more variations of exercise each week were significantly less likely to report depressive symptoms (adjusted (OR): 0.78; 95% CI 0.62-0.97; p = 0.025), and the likelihood of depression was also lower for women who engaged in one or more forms of exercise (adjusted OR: 0.82; 95% CI 0.71-0.94; p = 0.006). These findings support the association between depression and exercise and suggest that greater variations in regular exercise are associated with a reduction in depression for men whereas any form of exercise reduces the risk of depression in women.

Association of sleep duration and quality with elevated hs-CRP among healthy Korean adults

This study aimed to investigate the association of sleep duration and quality with high-sensitivity C-reactive protein (hs-CRP) among middle-aged and elderly Koreans. Among a total of 74,867 participants (25,069 men and 49,798 women) recruited for the Health Examinees (HEXA) study, adjusted geometric means of hs-CRP level were compared across categories of sleep duration (<6, 6–7, 8–9, and ≥10 hours) and sleep quality (difficulty in initiating sleep and maintaining sleep) using ANCOVA models. Odds ratios (ORs) and 95% confidence intervals (CIs) for elevated hs-CRP (>3 mg/L) associated with sleep characteristics were estimated using multivariable-adjusted logistic regression models. Men who slept ≥10 hours per day were significantly associated with elevated hs-CRP (OR = 1.47, 95% CI 1.11–1.95). Whereas in women, difficulty in initiating sleep (OR = 1.28, 95% CI 1.04–1.57 for “Always”), and maintaining sleep was significantly associated with elevated hs-CRP levels (OR = 1.13, 95% CI 1.02–1.26 for “Often”; OR = 1.11, 95% CI 0.97–1.28 for “Always”). Additionally, women who experienced poor sleep quality presented an elevated level of hs-CRP (OR = 1.13, 95% CI 1.03–1.23). Our findings suggest that excessive sleep duration and poor sleep quality are significantly associated with the elevated inflammatory marker, specifically hs-CRP. Further research is needed to examine the effect of sleep interventions focused on these factors.

Effects of sleep restriction on subjective and physiological variables in middle-aged Korean adults: an intervention study

BACKGROUND

Adequate sleep is crucial for normal functioning. However, most people, including middle-aged adults of reproductive age, show a marked reduction in their sleep duration. Thus, sleep is a major issue that should be addressed in health management. We investigated the effects of short-term sleep restriction on subjective parameters (sleepiness, stress, fatigue) and physiological parameters (cortisol, thyrotropin [TSH], thyroxine [T4], triiodothyronine [T3], C-reactive protein [CRP]) in middle-aged adults, the recovery of these parameters after rest, and the associations between parameters.

METHODS

A total of 118 healthy adults (59 men, 59 women), aged 35-44 years, and without sleep problems, were enrolled. Participants underwent a 4-h sleep restriction per day for 3 day at a hospital, and then returned to their daily lives to take four days of rest. A questionnaire and blood test were administered before and after sleep restriction, and after the recovery period, to assess subjective and physiological parameters.

RESULTS

After sleep restriction, sleepiness, fatigue, and stress significantly increased compared to baseline. Cortisol and TSH were elevated after sleep restriction, while T4, T3, and CRP were reduced compared to baseline. After the recovery phase, all parameters were restored to levels similar to baseline levels. Changes in each parameter were mutually associated; fatigue and sleepiness had the strongest association.

CONCLUSION

Our results suggest that even a short period of sleep restriction can have an adverse impact on psychological and physiological stress parameters in middle-aged adults, and that adequate rest and sleep are needed to restore them to normal levels.

Association of Sleep Duration and Obesity According to Gender and Age in Korean Adults: Results from the Korea National Health and Nutrition Examination Survey 2007-2015

BACKGROUND

This study aimed to investigate associations between self-reported sleep duration and general and abdominal obesity in Korean adults stratified according to gender and age.

METHODS

Data from 41,805 adults, 18-110 years of age, collected by the Korea National Health and Nutrition Examination Survey (KNHANES) in 2007 and 2015, were analyzed. Multivariable logistic regression was used to calculate adjusted odds ratios (AORs) and 95% confidence intervals (CIs) for obesity and abdominal obesity by sleep duration after controlling for sociodemographic and lifestyle variables.

RESULTS

Among individuals 30-49 years of age, there was an increased AOR for obesity only for sleep duration ≤ 5 hour/day compared with sleep duration 6 to 8 hour/day, both in men (OR, 1.25; 95% CI, 1.02-1.54) and women (OR, 1.56; 95% CI, 1.29-1.90), after controlling for covariates. Regarding women, there was increased AOR for abdominal obesity for sleep duration ≤ 5 hour/day (OR, 1.45; 95% CI, 1.18-1.78) and ≥ 9 hour/day (OR, 1.38; 95% CI, 1.09-1.76) compared with sleep duration 6 to 8 hour/day. However, for elderly individuals (≥ 65 years), there was a negative association between sleep duration ≤ 5 hour/day and obesity, but not with abdominal obesity, in both men and women.

CONCLUSION

This study demonstrated a significant association between sleep duration and obesity, which varied according to gender and age.