Nonrestorative sleep: symptom or unique diagnostic entity?

The simplified Chinese version of the Nonrestorative Sleep Scale in Chinese young adults and measurement invariance across language and age

BACKGROUND

To assess the psychometric properties of the simplified Chinese version of the Nonrestorative Sleep Scale (NRSS) in Chinese young adults and examine measurement invariance across language and age.

METHODS

After cognitive debriefing, the simplified Chinese NRSS was administered to university students in mainland China in this cross-sectional survey (Study 1). The Pittsburgh Sleep Quality Index (PSQI), the Patient Health Questionnaire (PHQ-4), and sociodemographic characteristics were also self-reported. The sample was randomly split into two halves to examine the scale structure using exploratory factor analysis (EFA) and asses the psychometric properties of the identified structure by confirmatory factor analysis (CFA), respectively. Incorporating data from two additional studies (Study 2: a survey of Hong Kong Chinese adults; Study 3: a survey of mainland Chinese adolescents), multigroup CFA models were conducted to examine the measurement invariance across language and age, followed by a t-test to determine group differences once invariance was established.

RESULTS

In the 570 participants of Study 1 (28.8% male, age 20.2 ± 1.5 years), the EFA revealed a four-factor structure. The root mean square error of approximation, comparative fit index, and standardized root mean square residual in the CFA model were 0.053, 0.995, and 0.054, respectively. The statistically significant correlations of NRSS with PSQI (r = - 0.61) and PHQ-4 (r = - 0.53) demonstrated the convergent validity of NRSS. The internal consistency of the whole scale was 0.84. Measurement invariance was concluded between traditional and simplified Chinese NRSS and between young adults and adolescents with the change of comparative fit index and root mean square error of approximation smaller than 0.010. The effect size (Cohen's d) of difference between mainland Chinese adults and Hong Kong Chinese adults ranged from 0.193 to 0.771, while that between mainland Chinese adults and adolescents ranged from 0.027 to 0.345.

CONCLUSION

The simplified Chinese 12-item NRSS is valid and reliable for assessing NRS among Chinese young adults, and it can be used to measure and compare NRS between individuals using simplified Chinese and traditional Chinese, as well as across different age groups within the simplified Chinese user population.

Associations between nonrestorative sleep and suicidal ideation: a Japanese general population survey

Insomnia symptoms and short sleep duration are known to be associated with suicidal ideation. The aim of this study was to investigate the association between nonrestorative sleep (NRS), a subjective experience of feeling unrefreshed after waking up, and suicidal ideation in the general population. We analyzed data from a cross-sectional survey of 2559 randomly sampled adults living in Japan. The participants were asked about insomnia symptoms (difficulty initiating sleep, difficulty maintaining sleep, and early morning awakening), NRS, sleep duration, and the presence of suicidal ideation. Logistic regression analysis was used to examine the associations among short sleep duration (< 6 h), insomnia symptoms, NRS, and suicidal ideation. Possible confounding factors were adjusted using propensity scores. In the multivariate analysis adjusting for the confounding effects of other sleep-related factors, in addition to psychiatric, sociodemographic, and lifestyle factors, only NRS showed a positive association with suicidal ideation (adjusted odds ratio [aOR] = 2.266). These findings suggest the importance of focusing on NRS for suicide prevention in the general population.

Association between non-restorative sleep and psychotic-like experiences among Chinese college students: A latent profile and moderated mediation analysis

BACKGROUND

Non-restorative sleep (NRS) is a core symptom of insomnia that has considerable consequences for daily life. However, the association between NRS and psychotic-like experiences (PLEs) remains unclear. The current study was designed to explore the relationship between NRS and PLEs as well as the mediation/moderation role of rumination and resilience among college students in China.

METHODS

3060 college students were recruited from two universities in South China from September 21st to October 26th, 2022. Non-restorative Sleep Scale, 8-item Positive Subscale of the Community Assessment of Psychic Experiences, Ruminative Response Scale, and 10-item Connor-Davidson Resilience Scale were administered. Latent profile analysis and moderated mediation analysis were performed.

RESULTS

11.3 % participants reported frequent PLEs in the past one month. Three profiles of rumination were identified and named as "low rumination" group (27.7 %), "medium rumination" group (55.3 %), and "high rumination" group (16.9 %). NRS directly predicted PLEs, and rumination played a significant mediation role between NRS and PLEs. Resilience significantly moderated the association between NRS and rumination as well as the association between NRS and PLEs.

CONCLUSIONS

NRS, rumination and resilience are important predictors to PLEs. Strategies on increasing restorative sleep, decreasing rumination, and enhancing resilience are of great significance in the prevention of PLEs.

Overtime work is related to nonrestorative sleep independently of short sleep time among a Japanese occupational population

OBJECTIVE

The symptoms of insomnia are defined as difficulty falling asleep, difficulty staying asleep, and early awakening. Although also a symptom of insomnia, nonrestorative sleep (NRS) is clearly more associated with objective indices than other insomnia symptoms. However, the link between NRS and overtime work duration is poorly understood.

METHODS

The results of a single year's medical examinations were investigated for 26,144 Japanese office workers who were 30 to 59 years old. NRS status and lifestyle were collected through a computer-assisted medical interview. The subjects were asked about the presence or absence of NRS and their lifestyles in the most recent two to three months. The subjects were asked about their sleep times and average overtime durations per month (< 20 h/month, ≥ 20 but < 40 h/month, ≥ 40 but < 60 h/month, and ≥ 60 h/month). The relationships between NRS and overtime work duration adjusted for sleep time were also analyzed.

RESULTS

The proportion of subjects with NRS showed a stepwise increase as overtime work hours increased. A logistic regression analysis was performed using NRS as an objective variable. The multivariate analysis demonstrated that overtime work duration (OR, 1.13; 95% CI 1.10-1.17; P < 0.001; per one-category increase) was an independent determinant of NRS.

CONCLUSION

For office workers, long hours of overtime work increased the NRS prevalence at any sleep duration.

Impact of chronotype, insomnia symptoms, sleep duration, and electronic devices on nonrestorative sleep and daytime sleepiness among Japanese adolescents

OBJECTIVES

Nonrestorative sleep (NRS) and excessive daytime sleepiness (EDS) are important indicators of daytime dysfunction. Electronic media use before bedtime greatly affects adolescent sleep quality. However, few studies have examined factors associated with these symptoms. Therefore, we aimed to investigate the impact of chronotype, electronic device use before bedtime, and insomnia symptoms on NRS and EDS in Japanese adolescents.

METHODS

A web-based cross-sectional survey of 2067 adolescents was conducted in 2022 to mainly assess sleep-related issues (sleep duration, chronotype, insomnia symptoms, NRS, and EDS), time spent using electronic devices, physical activity, and mental health.

RESULTS

We analyzed data of 1880 adolescents (age, 16.4 ± 0.8 years; males, 56.7%). NRS and EDS prevalence rates were 54.9% and 39.4%, respectively. In multivariate analysis, evening chronotype [odds ratio (OR): 2.14, 95% confidence interval (CI): 1.58-2.89], difficulty initiating sleep (OR: 1.94, 95% CI: 1.43-2.64), <5 h sleep (OR: 1.77, 95% CI: 1.24-2.54), 5-6 h sleep (OR: 1.52, 95% CI: 1.20-1.93), and using electronic devices just before bedtime (OR: 1.48, 95% CI: 1.08-2.04) were associated with NRS. Evening chronotype (OR: 1.40, 95% CI: 1.07-1.82), early morning awakening (OR: 1.60, 95% CI: 1.02-2.50), using electronic devices just before bedtime (OR: 2.08, 95% CI: 1.48-2.93), and using electronic devices 30 min before bedtime (OR: 1.57, 95% CI: 1.07-2.29) were associated with EDS.

CONCLUSION

Chronotype may be an important factor influencing NRS and EDS. Discontinuing electronic device use at least 30 min before bedtime could benefit affected adolescents.

Relationship between nonrestorative sleep and heartburn among a Japanese occupational population

BACKGROUND

Nonrestorative sleep (NRS) is a symptom of insomnia and is clearly more associated with objective indices than other insomnia symptoms. Gastroesophageal reflux disease (GERD) and insomnia are known to be strongly related. However, the link between NRS and heartburn, a main symptom of GERD, is poorly understood. Therefore, the relationships between them were investigated in addition to sleep duration.

METHODS

The results of a single year's medical examinations were investigated for 29,475 Japanese active office workers who were 20 to 59 years old. NRS and heartburn were investigated in a medical interview using a personal computer. The relationships between NRS and heartburn in addition to sleep duration were also analyzed.

RESULTS

The subjects were 46.6 ± 8.7 years old (mean ± SD) and 27% and 13% of them had NRS and heartburn, respectively. The presence of NRS together with a sleep duration of ≤ 5, 6, 7 or ≥ 8 hours was an independent comorbid factor for heartburn compared with the absence of NRS together with a sleep duration of seven hours (reference; odds ratio [OR], 2.38; 95% confidence interval [CI], 2.11-2.69, OR, 2.44; 95% CI, 2.16-2.76, OR, 2.33; 95% CI, 1.94-2.79; and OR, 1.72; 95% CI, 1.14-2.52). The absence of NRS together with a sleep duration of ≤ 5 hours was also an independent comorbid factor for heartburn compared with the reference (OR, 1.20; 95% CI, 1.05-1.37).

CONCLUSIONS

NRS in active workers may contribute to heartburn comorbidity despite the sleep duration as in other workers without NRS.

Relationship between nonrestorative sleep with short sleep duration and diabetes mellitus comorbid among a Japanese occupational population

Objective

Nonrestorative sleep (NRS) is one of the symptoms of insomnia and is clearly more associated with objective indices, such as sleep stability, sleep fragmentation, and inflammatory responses, than other insomnia symptoms. However, the link between NRS and diabetes mellitus is poorly understood. Therefore, the prevalence of NRS in workers and the relationships between NRS and diabetes were investigated.

Methods

The results of a single year's medical examinations were investigated for 26,144 Japanese active office workers who were 30 to 59 years old. NRS was investigated using a personal computer in a medical interview. Furthermore, the relationships between NRS and diabetes comorbidity in addition to sleep duration were also analyzed.

Results

The mean age of the subjects was 47.9 ± 7.3 years old, and the proportion of subjects with NRS was 26%. The presence of NRS together with a sleep duration ≤ 5 h or a sleep duration of 6 h was an independent comorbid factor for diabetes compared with the absence of NRS together with a sleep duration of 7 h (odds ratio [OR] 1.34; 95% confidence interval [CI] 1.14-1.58; P < 0.001; and OR 1.25; 95% CI 1.04-1.48; P = 0.015).

Conclusion

NRS in active workers may contribute to the development of diabetes even if the workers have the same short sleep durations as other workers without NRS.

Associations among Alcohol Drinking, Smoking, and Nonrestorative Sleep: A Population-Based Study in Japan

Nonrestorative sleep (NRS) is a common sleep disorder. It is associated with several unhealthy lifestyle factors, such as skipping breakfast and lack of exercise. However, the associations between alcohol drinking, smoking, and NRS are unclear. This study examined the prevalence of NRS within the Japanese general population and the relationships among alcohol drinking, smoking, and NRS. We analyzed an anonymized dataset from a 2013 nationwide population survey (35,717 men and 39,911 women). NRS was assessed through a single-item question, and socio-demographic and lifestyle factors were assessed through self-reports. Multivariable logistic regression analyses were used to examine the associations between alcohol drinking, smoking, and NRS. The total prevalence of NRS was 22.2% (95% CI 21.8-22.7) in men and 23.4% (95% CI 23.0-23.8) in women. Further, we found that sleep duration and prevalence of NRS shared an inverse J-shaped relationship. Heavy alcohol drinking was significantly associated with NRS in both sexes. Short sleep duration and certain socioeconomic factors modified the effect of smoking on NRS in men. These results could be useful in the development of more effective sleep health policies to establish better sleep hygiene.

Differences between subjective and objective sleep duration according to actual sleep duration and sleep-disordered breathing: the Nagahama Study

STUDY OBJECTIVES

Since subjective sleep duration (SSD) is considered to be longer than objective sleep duration (OSD), results of SSD minus OSD (SSD-OSD) might always be thought to be positive. Some recent reports showed different results, but exact results have not been obtained. The difference between SSD and OSD may change according to OSD. We investigated this difference and its association with sleep-disordered breathing (SDB) or nonrestorative sleep.

METHODS

This cross-sectional study evaluated 6,908 community residents in Nagahama, Japan. SSD was determined by self-administered questionnaire. OSD was measured by wrist actigraphy and sleep diary. SDB was assessed according to the 3% oxygen desaturation index adjusted for OSD.

RESULTS

Worthy of notice was that SSD was shorter than OSD for those with SSD longer than 6.98 hours in all participants, 7.36 hours in males, and 6.80 hours in females. However, SSD was longer than OSD (mean ± SD: 6.49 ± 1.07 vs 6.01 ± 0.96; P < .001) overall, as SSD is considered to be longer than OSD. In patients with SDB, the difference between SSD-OSD was greater when OSD was shorter. The difference also depended on SDB severity. The degree of positivity between OSD and SSD was a significant factor in nonrestorative sleep (odds ratio: 2.691; P < .001).

CONCLUSIONS

When OSD was slightly less than 7 (6.98) hours, participants reported or perceived SSD > OSD. When OSD was > 6.98 hours, participants reported or perceived SSD < OSD. Patients with SDB reported longer SSD than OSD according to severity of SDB. Evaluating SSD, OSD, and their differences may be useful for managing sleep disturbances, including nonrestorative sleep.

CITATION

Takahashi N, Matsumoto T, Nakatsuka Y, et al. Differences between subjective and objective sleep duration according to actual sleep duration and sleep-disordered breathing: the Nagahama Study. J Clin Sleep Med. 2022;18(3):851-859.

Mortality associated with nonrestorative short sleep or nonrestorative long time-in-bed in middle-aged and older adults

Associations of sleep duration with human health could differ depending on whether sleep is restorative. Using data from 5804 participants of the Sleep Heart Health Study, we examined the longitudinal association of sleep restfulness combined with polysomnography-measured total sleep time (TST) or time in bed (TIB), representing different sleeping behaviors, with all-cause mortality. Among middle-aged adults, compared with restful intermediate TST quartile, the lowest TST quartile with feeling unrested was associated with higher mortality (hazard ratio [HR], 1.54; 95% confidence interval [CI] 1.01–2.33); the highest TST quartile with feeling rested was associated with lower mortality (HR, 0.55; 95% CI 0.32–0.97). Among older adults, the highest TIB quartile with feeling unrested was associated with higher mortality, compared with restful intermediate TIB quartile (HR, 1.57; 95% CI 1.23–2.01). Results suggest a role of restorative sleep in differentiating the effects of sleep duration on health outcomes in midlife and beyond.

How does work impact daily sleep quality? A within-individual study using actigraphy and self-reports over the retirement transition

This study examined how the cessation of work at retirement affects daily measures of actigraphy-measured and self-rated sleep quality. Time in bed or asleep and stress at bedtime were examined as potential mechanisms. In total 117 employed participants who were aged 60-72 years and planned to retire soon were recruited to the Swedish Retirement Study. Sleep quality was measured in a baseline week using accelerometers, diaries, and questionnaires. Subjective sleep measures were sleep quality, restless sleep, restorative sleep, getting enough sleep, estimated wake after sleep onset, difficulties falling asleep, too early final awakening, and difficulties waking up. Actigraphy measures were sleep efficiency, wake after sleep onset, and average awakening length. After 1 and 2 years, the measurements were repeated for the now retired participants. Daily variations in sleep quality before and after retirement were analysed using multilevel modelling, with time in bed or asleep and stress at bedtime as potential mediators. We found that several self-reports of sleep improved (e.g., +0.2 standard deviations for sleep quality and +0.5 standard deviations for restorative sleep) while objective sleep quality remained unchanged or decreased slightly with retirement (e.g., -0.8% for sleep efficiency). Increased time in bed or asleep and stress at bedtime accounted partially for the improvements in self-rated sleep quality at retirement. In conclusion, actigraph-measured and self-reported sleep quality do not change in concert at retirement, highlighting the interest of studying both outcomes. The main effects of retirement from work concern subjective experiences of recovery more than sleep quality per se.

Insomnia and other sleep-related problems during the remission period of the COVID-19 pandemic: A large-scale survey among college students in China

This study aimed to evaluate the sleep-related problems and predictors of probable clinical insomnia among college students during the COVID-19 remission period in China. 146,102 college students from 22 colleges/universities in Guangdong province participated in this study from 1th to 15th June, 2020. Self-administered questionnaires were used to assess demographic characteristics. Sleep-related problems, depression and anxiety symptoms were measured by Youth Self-Rating Insomnia Scale, Patient Health Questionnaire-9 and Generalized Anxiety Disorder Scale-7, respectively. The prevalence of difficulty in initiating sleep, difficulty in maintaining sleep, early morning awakening, sleep insufficiency, unrefreshing sleep and daytime functioning impairment were 7.2%, 3.4%, 3.5%, 9.6%, 14.6%, and 7.6%, respectively. 16.9% students had varying degrees of insomnia and 6.3% were considered as displaying probable clinical insomnia. Moreover, being urban residents, having a history of physical or mental illness, and probable clinical depression or anxiety were significant risk factors of probable clinical insomnia, while college senior degree and 7-8 hours' sleep duration per day was the protective factor for probable clinical insomnia. Unrefreshing sleep was the most prominent sleep problem among college students during COVID-19 remission in China. Good sleep hygiene practices are strongly suggested to develop in the time of prolonged home isolation.

Nonrestorative sleep scale: a reliable and valid short form of the traditional Chinese version

Purpose

Previous research has suggested the essential unidimensionality of the 12-item traditional Chinese version of the Nonrestorative Sleep Scale (NRSS). This study aimed to develop a short form of the traditional Chinese version of the NRSS without compromising its reliability and validity.

Methods

Data were collected from 2 cross-sectional studies with identical target groups of adults residing in Hong Kong. An iterative Wald test was used to assess differential item functioning by gender. Based on the generalized partial credit model, we first obtained a shortened version such that further shortening would result in substantial sacrifice of test information and standard error of measurement. Another shortened version was obtained by the optimal test assembly (OTA). The two shortened versions were compared for test information, Cronbach’s alpha, and convergent validity.

Results

Data from a total of 404 Chinese adults (60.0% female) who had completed the Chinese NRSS were gathered. All items were invariant by gender. A 6-item version was obtained beyond which the test performance substantially deteriorated, and a 9-item version was obtained by OTA. The 9-item version performed better than the 6-item version in test information and convergent validity. It had discrimination and difficulty indices ranging from 0.44 to 2.23 and − 7.58 to 2.13, respectively, and retained 92% of the test information of the original 12-item version.

Conclusion

The 9-item Chinese NRSS is a reliable and valid tool to measure nonrestorative sleep for epidemiological studies.

Electronic supplementary material

The online version of this article (10.1007/s11136-020-02523-4) contains supplementary material, which is available to authorized users.

Linking Nonrestorative Sleep and Activity Interference Through Pain Catastrophizing and Pain Severity: An Intraday Process Model Among Individuals With Fibromyalgia

Nonrestorative sleep is a key diagnostic feature of the musculoskeletal pain disorder fibromyalgia and is robustly associated with poor physical functioning, including activity interference. However, the mechanisms through which nonrestorative sleep elicits activity interference among individuals with fibromyalgia at the within-person level remain unclear. The present study tested the following 3-path mediation model, using data gathered from a 21-day electronic daily diary in 220 individuals with fibromyalgia: previous night nonrestorative sleep → morning pain catastrophizing → afternoon pain severity → end-of-day activity interference. Results of multilevel structural equation modeling supported the 3-path mediation model. Previous night's nonrestorative sleep and morning pain catastrophizing were also directly related to end-of-day activity interference. Previous night nonrestorative sleep did not significantly predict afternoon pain severity while controlling for the effect of morning pain catastrophizing. Greater nonrestorative sleep during the previous night and a higher level of morning pain catastrophizing appear to serve as risk factors for experiencing greater daily pain and activity interference later in the day. These findings point to the potential utility of targeted interventions that improve both sleep quality and pain catastrophizing to help individuals with chronic pain engage in important daily activities despite experiencing pain. PERSPECTIVE: This study provides a better understanding of how nonrestorative sleep is associated with daily activity interference among individuals with fibromyalgia. An intervention that targets attenuating nonrestorative sleep and pain catastrophizing may help improve daily physical functioning of this population.

Sleep before and after work-related concussion: Sex differences in effects and functional outcomes

BACKGROUND

Recent studies have started disentangling components of disturbed sleep as part of the post-concussive syndrome, but little is known about the workers with an injury' perspectives on post-injury sleep changes or what causes these changes.

OBJECTIVES

To determine the effects of work-related concussion/mild traumatic brain injury (wr-mTBI) on perceptions of refreshing sleep in workers with an injury and to identify the relevant factors responsible for sleep changes.

METHODS

We studied post-concussive changes in sleep in 66 adults (50% male workers, 42% aged 30-50 years, median post-injury days: 155) who had sustained wr-mTBI and experienced functional limitations long after the injury. We collected sociodemographic, occupational and health status data and identified variables related to post-concussive changes in refreshing sleep.

RESULTS

Forty-seven workers with wr-mTBI (79% of male workers, 64% of female workers) perceived their sleep as being refreshing before injury and unrefreshing afterwards (χ2 = 67.70 for change, χ2 = 27.6 for female and χ2 = 41.1 for male workers, p < 0.0001). Post-concussive losses in refreshing sleep were associated with socio demographic, occupational, and health status data variables. Sex stratification revealed differences between male and female workers.

CONCLUSIONS

Workers with wr-mTBI experience clinically meaningful changes in refreshing sleep that are associated with modifiable variables. The observed differences in functional outcomes between male and female workers warrant further study.

Reciprocal relations between work stress and insomnia symptoms: A prospective study

Work stress and poor sleep are closely related in cross-sectional data, but evidence from prospective data is limited. We analysed how perceived stress and work stressors (work demands, decision authority and workplace social support) are related to key dimensions of insomnia over time, using structural equation modelling. Biennial measurements from a large sample of the working population in Sweden enabled us to analyse both the relationship from stress to sleep as well as that from sleep to stress. Overall, we found reciprocal relations between insomnia and all four stress measures. However, looking at the relation between each dimension of insomnia and each stress measure, there were some differences in direction of effects. In the direction from stress to sleep, all work stressors as well as perceived stress predicted both difficulties initiating sleep and difficulties maintaining sleep. The same was found for non-restorative sleep, with the exception for decision authority. In the opposite direction, difficulties maintaining sleep predicted increased levels of work demands and perceived stress. Difficulties initiating sleep stood out among the insomnia symptoms as not predicting any of the stress measures, while non-restorative sleep was the only symptom predicting all stress measures. The results advance the understanding of the stress-sleep relationship and indicate a potential vicious circle between insomnia and perceived stress as well as work stressors, suggesting that the workplace could be an arena for interventions to alleviate insomnia.

Insomnia: Risk Factor for Neurodegenerative Diseases

Insomnia can be defined as difficulty falling asleep or maintaining sleep, waking up earlier than expected, or having non-restorative sleep. It is one of the most common sleep disorders in the world. Insomnia is a common symptom of many neurodegenerative diseases but only recently has it been found that it is a risk factor for neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. We did a traditional review to analyze the relationship between insomnia and neurodegenerative diseases. We analyzed all the relevant articles on Pubmed and included studies done on humans over the last 10 years with full text available. After reviewing the available literature on Pubmed, we conclude that insomnia is an important risk factor for neurodegenerative diseases. In addition, insomnia and neurodegenerative disorders have a complex and bi-directional relationship. We think it requires further study to understand the sole contribution of insomnia to the development of various neurodegenerative diseases when different factors like mood problems, genetic factors, and environmental factors also contribute to the disease. It would also be advisable to use cognitive screening questionnaires in all sleep clinics in insomnia patients over 50 years of age to diagnose dementia early and to gather more sleep study data for prospective and retrospective research. The role of hypnotics in preventing neurodegenerative diseases through treating insomnia should also be assessed.

Interacting Influences of Sleep, Pain, and Analgesic Medications on Sleep Studies in Rodents

This overview provides a brief summary of the complex interactions that link sleep, pain, and analgesic medications. Sleep scientists and clinicians are well aware of these relationships and understand that maintaining healthy pain-free subjects in a stable environment is essential to generating interpretable data and valid conclusions. However, these concepts and the data that support bidirectional interactions between sleep and pain may be less known to those who are not sleep scientists yet need such information to protect and advance both animal wellbeing and research validity (for example, veterinarians, IACUC members). Abundant human evidence supports the disruptive effect of pain and the modulatory effects of analgesic drugs on sleep; however, analgesic drugs can alter both sleep and the electroencephalogram, which is the primary objective measure for identifying sleep and evaluating sleep properties in both humans and animals. Consideration of the modulatory and interactive relationships of sleep, pain, and analgesic medications is essential to designing and conducting valid and reproducible sleep research using animal subjects.

Nonrestorative sleep scale: reliable and valid for the Chinese population

PURPOSE

To conduct a linguistic and psychometric evaluation of a Chinese version of the Nonrestorative Sleep Scale (NRSS).

METHODS

The Chinese NRSS was created from a standard forward-backward translation and trialed on 10 Chinese adults. Telephone interviews were then conducted with 100 adults, who completed the Chinese NRSS, the Pittsburgh Sleep Quality Index (PSQI), the Athens Insomnia Scale (AIS), the Center for Epidemiological Studies Depression Scale (CES-D), and the Toronto Hospital Alertness Test (THAT). A household survey was conducted with 20 subjects, followed by a confirmatory factor analysis (CFA), and a bifactor model was developed to evaluate the reliability and validity of the NRSS.

RESULTS

The bifactor model had the root mean square error of approximation (RMSEA), standardized root mean square residual (SRMR), and comparative fit index (CFI) of 0.06, 0.06, and 0.97, respectively. Convergent validity was shown from the moderate associations with PSQI (r = - 0.66, P < 0.01), AIS (r = - 0.65, P < 0.01), CES-D (r = - 0.54, P < 0.01), and THAT (r = 0.68, P < 0.01). The coefficient omega (0.92), omega hierarchical (0.81), factor determinacy (0.93), H value (0.91), explained common variance (0.63), and percentage of uncontaminated correlations (0.80) derived from the bifactor CFA supported the essential unidimensionality of NRSS.

CONCLUSIONS

The Chinese NRSS is a valid and reliable essential unidimensional tool for the assessment of nonrestorative sleep in the Chinese population.

Comparison of sleep structure and psychometric profiles in patients with fibromyalgia, osteoarthritis and healthy controls

While research indicates that both the macro- and microstructure of sleep may be altered in fibromyalgia syndrome, few studies have controlled for symptom duration or included pain-control participants (i.e. patients with chronic pain and sleep disturbance not associated with fibromyalgia syndrome). A frequently reported alteration found in the sleep microstructure of patients with fibromyalgia syndrome is the alpha-delta sleep anomaly. Although alpha waves have been observed during N3 sleep in healthy individuals, it has been proposed that there is an increase in alpha wave activity during slow-wave sleep in fibromyalgia syndrome. Originally considered a possible neurological contribution to fibromyalgia syndrome, whether the alpha-delta sleep anomaly is fundamental to the development of fibromyalgia syndrome, or results mainly from the pain experience remains unknown. The present study was designed to compare sleep macro- and microstructure, and psychometric profiles, in three broadly age-matched groups of female participants: patients with fibromyalgia syndrome (n = 19); patients with osteoarthritis with sleep disturbance (n = 17); and healthy adults (n = 10). Patients with fibromyalgia syndrome met the American College of Rheumatology diagnostic criteria and were recruited within 6 months of diagnosis. Subjective sleep quality was significantly lowest, and levels of anxiety and depressive symptoms were significantly highest for patients with fibromyalgia syndrome. However, the groups showed no significant differences in polysomnographic measures of total sleep time, sleep latency and total wake after sleep onset. Levels of alpha-delta sleep were statistically similar in both clinical (fibromyalgia syndrome and osteoarthritis) groups, indicating that it is not a specific abnormality of fibromyalgia syndrome. Overall, subjective measurements of anxiety, depression, fatigue and sleep quality better discriminated between the three groups than did objective measurements of sleep variables.

Sleep Difficulties and Insomnia Symptoms in Norwegian Musicians Compared to the General Population and Workforce

Sleep problems are reported as common among performing artists and musicians. However, epidemiological research comparing musicians to different groups of the general population is lacking. For this study, 4,168 members of the Norwegian Musician's Union were invited to an online survey regarding work and health. Of the 2,121 (51%) respondents, 1,607 were active performing musicians. We measured prevalence of insomnia symptoms using the Bergen Insomnia Scale (BIS), and compared this sample to a representative sample of the general Norwegian population (n = 2,645). Overall, musicians had higher prevalence of insomnia symptoms compared to the general population (Prevalence Difference 6.9, 95% Confidence Interval 3.9-10.0). Item response analysis showed that this difference was mainly explained by nonrestorative sleep and dissatisfaction with sleep among musicians. An additional analysis, comparing musicians to the general Norwegian workforce (n = 8,518) on sleep difficulties, confirmed this tendency (Prevalence Difference 6.2, 95% Confidence Interval 4.3-8.1). Musicians performing classical, contemporary, rock, and country music reported the highest prevalence of insomnia, and these genres might be of special interest when developing preventative measures, treatment strategies, and further research on sleep difficulties among musicians.

The Neurological Sleep Index: A suite of new sleep scales for multiple sclerosis

Objective

The objective of this study was to develop patient-reported outcome measures for sleep dysfunction and sleepiness in multiple sclerosis (MS), since there are currently no MS-specific measurement tools for these clinically important entities.

Methods

Items were generated from semi-structured interviews followed by cognitive debrief. A 42-item pool was administered to patients with MS at three neuroscience centres in the UK. Comparator scales were co-administered. Constructs were validated by Rasch analysis, guided by initial exploratory factor analysis.

Results

There were two supraordinate qualitative themes of diurnal sleepiness and non-restorative nocturnal sleep. Rasch analysis on 722 records produced three scales, which corresponded to diurnal sleepiness, non-restorative nocturnal sleep and fragmented nocturnal sleep. All had excellent fit parameters, were unidimensional and were free from differential item functioning. A summed raw score cut-point of 31/48 in the Diurnal Sleepiness Scale equated to the standard cut-point of 10 on the Epworth Sleepiness Scale (ESS).

Conclusion

Three high-quality measurement scales were developed, and together they compose the Neurological Sleep Index for MS (NSI-MS). The Diurnal Sleepiness Scale might provide an alternative to the ESS. The Non-Restorative Nocturnal Sleep Scale and the Fragmented Nocturnal Sleep Scale appear to be the only such measures for use in MS.

Neural Reward Processing Mediates the Relationship between Insomnia Symptoms and Depression in Adolescence

STUDY OBJECTIVES

Emerging evidence suggests that insomnia may disrupt reward-related brain function-a potentially important factor in the development of depressive disorder. Adolescence may be a period during which such disruption is especially problematic given the rise in the incidence of insomnia and ongoing development of neural systems that support reward processing. The present study uses longitudinal data to test the hypothesis that disruption of neural reward processing is a mechanism by which insomnia symptoms-including nocturnal insomnia symptoms (NIS) and nonrestorative sleep (NRS)-contribute to depressive symptoms in adolescent girls.

METHOD

Participants were 123 adolescent girls and their caregivers from an ongoing longitudinal study of precursors to depression across adolescent development. NIS and NRS were assessed annually from ages 9 to 13 years. Girls completed a monetary reward task during a functional MRI scan at age 16 years. Depressive symptoms were assessed at ages 16 and 17 years. Multivariable regression tested the prospective associations between NIS and NRS, neural response during reward anticipation, and the mean number of depressive symptoms (omitting sleep problems).

RESULTS

NRS, but not NIS, during early adolescence was positively associated with late adolescent dorsal medial prefrontal cortex (dmPFC) response to reward anticipation and depressive symptoms. DMPFC response mediated the relationship between early adolescent NRS and late adolescent depressive symptoms.

CONCLUSIONS

These results suggest that NRS may contribute to depression by disrupting reward processing via altered activity in a region of prefrontal cortex involved in affective control. The results also support the mechanistic differentiation of NIS and NRS.

Measurement properties of the minimal insomnia symptom scale as an insomnia screening tool for adults and the elderly

BACKGROUND

The psychometric properties of the three-item Minimal Insomnia Symptom Scale (MISS) were evaluated using the classical test theory. Different cut-offs for identifying insomnia were suggested in two age groups (≥6 and ≥7 among adult and elderly people, respectively). The aim of the present study was to test the measurement properties of the MISS using the Rasch measurement model, with special emphasis on differential item functioning by gender and age.

METHODS

Cross-sectional MISS data from adult (age 20-64 years, n = 1075) and elderly (age 65+, n = 548) populations were analysed using the Rasch measurement model.

RESULTS

Data generally met Rasch model requirements and the scale could separate between two distinct groups of people. Differential item functioning was found by age but not gender. The difference between the adult and elderly samples was lower for the originally recommended ≥6 points cut-off (0.09 logits) than for the ≥7 points cut-off (0.23 logits), but greater at the lower and higher ends of the scale.

CONCLUSIONS

This study provides general support for the measurement properties of the MISS. Caution should be exercised in comparing raw MISS scores between age groups, but applying a ≥6 cut-off appears to allow for valid comparisons between adults and the elderly regarding the presence of insomnia. Nevertheless, additional studies are needed to determine the clinically optimal cut-score for identification of insomnia.

Insomnia symptoms and risk for unintentional fatal injuries--the HUNT Study

STUDY OBJECTIVES

To assess the association between insomnia symptoms and risk of fatal unintentional injuries.

DESIGN

Population-based prospective cohort study with a mean follow-up of 14 y, linking health survey data with information on insomnia symptoms to the National Cause of Death Registry.

SETTING

Nord-Trøndelag County, Norway.

PARTICIPANTS

A total of 54,399 men and women 20-89 y of age who participated in the Nord-Trøndelag Health Study between 1995 and 1997.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

There were 277 unintentional fatal injuries, including 57 fatal motor vehicle injuries during follow-up. There was a dose-dependent association between the number of insomnia symptoms and risk of unintentional fatal injuries (P for trend 0.001) and fatal motor vehicle injuries (P for trend 0.023), respectively. The proportion of unintentional fatal injuries cases that could have been prevented in the absence of difficulties initiating sleep, difficulties maintaining sleep, and having a feeling of nonrestorative sleep were 8%, 9%, and 8%, respectively. The corresponding estimates for motor vehicle injuries were 34%, 11%, and 10%.

CONCLUSION

Insomnia is a major contributor to both unintentional fatal injuries in general as well as fatal motor vehicle injuries. Increasing public health awareness about insomnia and identifying persons with insomnia may be important in preventing unintentional fatal injuries.

Development and evaluation of a measure to assess restorative sleep

BACKGROUND

There are validated measures assessing insomnia and disturbed sleep, but few psychometrically sound instruments to assess perceptions of the restorative or inadequate properties of sleep are available.

STUDY OBJECTIVES

To develop and evaluate a new instrument, the Restorative Sleep Questionnaire (RSQ).

DESIGN AND SETTING

Focus groups were conducted using participants with and without nonrestorative sleep complaints. Questions were designed to elicit the feelings and experiences people have about their sleep and their view of daytime consequences of sleep. Expert panels confirmed the importance of nonrestorative sleep (NRS) as a frequently encountered problem either with or without other sleep complaints. The resulting RSQ was administered in three studies: (1) a telephone interview with healthy controls and individuals with sleep problems; (2) a randomized clinical trial of patients with primary insomnia assessed by polysomnography (PSG); (3) a PSG study of subjects with NRS complaints.

MEASUREMENT AND RESULTS

Across all studies, the new measures were shown to be significantly correlated with health-related quality of life (HRQL) domains hypothesized to be related to NRS. The RSQ had good psychometric properties (α > 0.90; rtest-retest > 0.80), and factor analysis confirmed the unidimensionality of the measure. The RSQ was able to distinguish between healthy controls, patients with primary insomnia, and insomnia patients with isolated NRS complaints but without PSG defined sleep onset, duration, or maintenance problems. Normal sleepers reported sleep that was about a standard deviation more restorative than that of those with NRS on the RSQ.

CONCLUSIONS

The results of the study provide support for the reliability and validity of the RSQ as a measure of NRS in subjects with and without self-reported or PSG confirmed sleep initiation and maintenance difficulties.

CLINICALTRIALSGOV IDENTIFIERS

NCT00655369; NCT00705601.

Development and validation of the Nonrestorative Sleep Scale (NRSS)

STUDY OBJECTIVES

Nonrestorative sleep (NRS) is defined as the subjective feeling that sleep has been insufficiently refreshing, often despite the appearance of physiologically normal sleep. While NRS has been shown to be associated with a variety of cognitive, affective, and medical complaints, there is currently no valid, reliable instrument available in the public domain for its assessment. The purpose of this study was to develop and validate the nonrestorative sleep scale (NRSS).

PARTICIPANTS

The scale was administered to a sample of 226 (age: 46.7 ± 14.9 years; gender: 48% female) consecutive sleep clinic patients and to 30 control participants (age: 36.9 ± 12.5; gender: 53% female).

RESULTS

Data screening led to a final instrument of 12 items, and factor analysis resulted in 4 factors accounting for 73.2% of total variance. The scale demonstrated excellent internal reliability (α = 0.88) and good test-retest reliability (r = 0.72). Preliminary evaluations of construct validity found that certain subscales correlated reasonably well with previously validated sleep, alertness, and affective scales. Comparisons between global NRSS scores and objective polysomnographic variables revealed a few very small but significant correlations.

CONCLUSIONS

Based on these findings, the NRSS was confirmed to be a valid and reliable tool for the assessment of nonrestorative sleep.

Sleep and daytime function in adults with attention-deficit/hyperactivity disorder: subtype differences

OBJECTIVES

Although sleep disorders have been reported to affect more than half of adults with attention-deficit/hyperactivity disorder (ADHD), the association between sleep and ADHD is poorly understood. The aims of our study were to investigate sleep-related variables in adults with ADHD and to assess if any differences exist between ADHD of the predominantly inattentive (ADHD-I) and combined (ADHD-C) subtypes.

METHODS

We used the Epworth sleepiness scale (ESS), the Pittsburgh Sleep Quality Index (PSQI), and the fatigue severity scale (FSS) to collect data on daytime sleepiness, sleep quality, and fatigue in 126 subjects (45 ADHD-I and 81 ADHD-C subjects).

RESULTS

Approximately 85% of subjects reported excessive daytime sleepiness or poor sleep quality. The most common sleep concerns were initial insomnia, interrupted sleep, and feeling too hot. When examining ADHD subtype differences, ADHD-I subtypes reported poorer sleep quality and more fatigue than ADHD-C subtypes. Partial correlation analyses revealed that interrelationships between sleep quality, daytime sleepiness, and fatigue differ between ADHD subtypes; in ADHD-I subtypes fatigue was associated with sleep quality, while in the ADHD-C subtypes fatigue was associated with both sleep quality and daytime sleepiness. There also appears to be a subtype×gender interaction that affects the perception of fatigue, as subjective fatigue was markedly higher in ADHD-I women than in ADHD-C women.

CONCLUSION

Altogether our data indicate that the interplay of variables associated with daytime function and sleep varies between ADHD subtypes. This finding may have considerable relevance in the management and pathophysiologic understanding of ADHD, and thus lead to tailored treatments for ADHD subtypes.

Differentiating nonrestorative sleep from nocturnal insomnia symptoms: demographic, clinical, inflammatory, and functional correlates

STUDY OBJECTIVES

Recent studies have suggested that nonrestorative sleep (NRS) symptoms may be distinct from nocturnal insomnia symptoms (NIS). However, there is limited information on the demographic, medical, and biologic correlates of NRS independent from NIS in the general population. This report presents the sociodemographic correlates, patterns of comorbidity with other sleep and physical disorders, C-reactive protein (CRP) levels, and general productivity associated with NIS and NRS in a nationally representative sample of US adults.

DESIGN

National Health and Nutrition Examination Survey (NHANES).

SETTING

The 2005-2008 surveys of the general population in the United States.

PARTICIPANTS

There were 10,908 individuals (20 years or older).

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Respondents were classified by the presence or absence of NIS and NRS. Compared with those without insomnia symptoms, respondents with NIS were older and had lower family income and educational levels than those with NRS. In addition, there was a significant association between NIS and cardiovascular disease, whereas NRS was associated with other primary sleep disorders (including habitual snoring, sleep apnea, and restless legs syndrome), respiratory diseases (emphysema and chronic bronchitis), thyroid disease, and cancer as well as increased CRP levels. In addition, the study participants with NRS only reported poorer scores on the Functional Outcomes of Sleep Questionnaire (FOSQ) than those without insomnia symptoms or those with NIS only.

CONCLUSIONS

These findings suggest that there are substantial differences between NIS and NRS in terms of sociodemographic factors, comorbidity with other sleep and physical disorders, increased CRP level, and functional impairment. An inflammatory response might play a unique role in the pathogenesis of NRS.