Intraindividual Variability In Sleep Research Articles

Characteristics of sleep in children with heavy prenatal alcohol exposure.

Sleep plays an important role in neurodevelopment. However, the effects of prenatal alcohol exposure on sleep quality have been understudied, despite reports of sleep disturbance in infants prenatally exposed to alcohol and elevated levels of sleep problems reported by caregivers of children with fetal alcohol spectrum disorders. The current study characterizes sleep in children with prenatal alcohol exposure using both objective (actigraphy) and subjective (questionnaires, sleep diaries) methods. Participants aged 6-10 years, with and without prenatal alcohol exposure, were included in the study (alcohol-exposed [AE]: n = 35; control [CON]: n = 39). Objective sleep was measured via 24-h actigraphy for 2 weeks. Parents completed sleep diaries and sleep questionnaires (Children's Sleep Habits Questionnaire, Pediatric Sleep Questionnaire). Multivariate analysis of variance was used to characterize the sleep profile (objective, subjective) and examine group differences. There were no group differences on actigraphy metrics averaged across 2 weeks. However, the AE group showed significantly greater intraindividual variability on most actigraphy measures, particularly total sleep time, percent sleep, wake after sleep onset, and number of wake bouts. Parents reported significantly more sleep problems in the AE group than in the CON group, primarily driven by night wakings, parasomnias (e.g., sleepwalking), snoring, and daytime sleepiness. These effects were more severe in children >8.5 years of age. Despite similar 2-week average sleep outcomes, children with prenatal alcohol exposure showed greater intraindividual sleep variability and parents reported more sleep problems related to sleep behavior and snoring. These difficulties with sleep may be related to other cognitive and behavioral outcomes. Importantly, sleep is a modifiable behavior, and interventions that focus on variability in sleep, particularly in sleep duration, can impact the quality of life in children with prenatal alcohol exposure and their families.

Objective and Subjective Intraindividual Variability in Sleep: Predisposing Factors and Health Consequences.

We investigated the factors that predispose or precipitate greater intra-individual variability (IIV) in sleep. We further examined the potential consequences of IIV to overall sleep quality and health outcomes, including whether these relationships were found in both self-reported and actigraphy-measured sleep IIV. In Study 1, 699 US adults completed a Sleep Intra-Individual Variability questionnaire and self-reported psychosocial, sleep quality, and health outcomes. In Study 2, 100 university students wore actigraphy and completed psychosocial, sleep, and health surveys at multiple timepoints. In cross-sectional analyses that controlled for mean sleep duration, predisposing/precipitating factors to greater IIV were being an under-represented racial/ethnic minority (Study 1: F = 13.95, p < .001; Study 2: F = 7.03, p = .009), having greater stress (Study 2: r values ≥ 0.32, p values ≤ 0.002) or trait vulnerability to stress (Study 1: rs ≥ 0.15, ps < 0.001), and showing poorer time management (Study 1: r = -0.23, p < 0.001; Study 2: rs ≤ -0.26, ps ≤ 0.013). In addition, both studies showed that greater sleep IIV was associated with decreased overall sleep quality, independent of mean sleep duration (Study 1: rs ≥ 0.20, ps < 0.001; Study 2: rs ≥ 0.33, ps ≤ 0.001). Concordance across subjective and objective IIV measures was modest (rs: 0.09-0.35) and similar to concordance observed for subjective-objective mean sleep duration measures. Risk for irregular sleep patterns is increased in specific demographic groups and may be precipitated by, or contribute to, higher stress and time management inefficiencies. Irregular sleep may lead to poor sleep quality and adverse health outcomes, independent of mean sleep duration, underscoring the importance of addressing sleep consistency.

Effects of daily fluctuations in seep and intraindividual sleep variability on mood, motivation and sleepiness in university students: a wearable and digital diary approach

Effects of daily fluctuations in seep and intraindividual sleep variability on mood, motivation and sleepiness in university students: a wearable and digital diary approach

Assessing ‘readiness’ by tracking fluctuations in daily sleep duration and their effects on daily mood, motivation, and sleepiness

Study objectivesConsumer sleep trackers issue daily guidance on ‘readiness’ without clear empirical basis. We investigated how self-rated mood, motivation, and sleepiness (MMS) levels are affected by daily fluctuations in sleep duration, timing, and efficiency and overall sleep regularity. We also determined how temporally specific these associations are. Methods119 healthy university students (64 female, mean age = 22.54 ± 1.74 years) wore a wearable sleep tracker and undertook twice-daily smartphone-delivered ecological momentary assessment of mood, motivation, and sleepiness at post-wake and pre-bedtime timings for 2–6 weeks. Naps and their duration were reported daily. Nocturnal sleep on 2471 nights were examined using multilevel models to uncover within-subject and between-subject associations between sleep duration, timing, efficiency, and nap duration on following day MMS ratings. Time-lagged analyses examined the temporal specificity of these associations. Linear regression models investigated associations between MMS ratings and sleep variability, controlling for sleep duration. ResultsNocturnal sleep durations were short (6.03 ± 0.71 h), and bedtimes were late (1:42AM ± 1:05). Within-subjects, nocturnal sleep longer than a person's average was associated with better mood, higher motivation, and lower sleepiness after waking. Effects of such longer sleep duration lingered for mood and sleepiness till the pre-bedtime window (all Ps < .005) but did not extend to the next day. Between-subjects, higher intraindividual sleep variability, but not sleep duration, was associated with poorer mood and lower motivation after waking. Longer average sleep duration was associated with less sleepiness after waking and lower motivation pre-bedtime (all Ps < .05). Longer naps reduced post-nap sleepiness and improved mood. Controlling for nocturnal sleep duration, longer naps also associated with lower post-waking sleepiness on the following day. ConclusionsPositive connections between nocturnal sleep and nap duration with MMS are temporally circumscribed, lending credence to the construction of sleep-based, daily ‘readiness’ scores. Higher sleep duration variability lowers an individual's post waking mood and motivation. Clinical trial idClinicalTrials.gov NCT04880629.

Intraindividual variability in sleep among athletes: A systematic review of definitions, operationalizations, and key correlates.

Via systematic review with narrative synthesis of findings, we aimed to document the ways by which researchers have defined, operationalized, and examined sleep variability among athletes. We identified studies in which scholars examined intraperson variability in sleep among athletes via a search of six databases (Web of Science, Embase, Medline, PsycINFO, CINHAL Plus, and ProQuest Dissertations and Theses Global) using a protocol that included keywords for the target outcome (sleep*), population (athlet* OR sport*), and outcome operationalization (variability OR variation OR "standard deviation" OR fluctuate OR fluctuation OR stability OR instability OR reactivity OR IIV OR intraindividual). We complemented this primary search with citation searching of eligible articles. Assessments of study quality captured eight core elements, namely aims/hypotheses, sample size justification, sample representativeness, number of days sleep assessed, measures of sleep and its correlates, missing data, and inferences and conclusions. From a total of 1209 potentially relevant papers, we identified 16 studies as meeting our eligibility criteria. Concept definitions of variability were notably absent from this work and where available were vague. Quantitative deviations from one's typical level of target sleep metrics reflected the essence by which all but one of the research teams operationalized sleep variability. We assessed the overall quality of empirical work as moderate in nature. We propose a working definition of sleep variability that can inform knowledge generation on the temporal, day-to-day dynamics of sleep functioning that is required for personalized interventions for optimizing sleep health.

0102 Are there associations between intraindividual variability in sleep and mental health among adolescents reporting alcohol use?

Abstract Introduction Considering the increasing number of studies that report on ecological momentary assessment by uses of sleep diary and actigraphy, it may also be valuable to consider the relationship between fluctuations that exists in sleep measures on adolescent health outcomes. Above the impact of mean sleep measures, intraindividual variability (IIV) in sleep provides information on the degree to which daily variations or fluctuations in sleep/wake patterns are occurring and may prompt important cues to adolescents’ health outcome. The present study examined the objective IIV in sleep and its relationship to their sleep and mental health outcomes among adolescents with history of alcohol use. Methods The study analyzed 8 days of wrist actigraphy data from 72 high school students reporting prior alcohol use (58.3% female; mean age 17.0 years). Bayesian variability method using varian (R package) was performed to calculate IIV in total sleep time (TST), time in bed (TIB), midpoint sleep, bedtime, and risetime. Participants also completed Pittsburgh Sleep Quality Index (PSQI), Cleveland Adolescent Sleepiness Questionnaire (CASQ), Inventory of Depressive Symptomatology (IDS-SR-30), Chapman’s Inventories – Social Anhedonia (CHAPSAS), and Rutgers Alcohol Problem Index (RAPI). Multiple linear regression models were adjusted for biological sex, age, and the sum of alcohol drinks in the past 3 months. Results Participants reported average of 18.52 (SD=23.10) total drinks consumed over the past 3 months. IIV in TST, TIB, and risetime were associated with lower sleep quality (B=3.04, 95% CI, 0.02, 7.39, p&amp;lt; 0.05 for IIV in TST; B=2.87, 95% CI, 0.39, 5.88, p&amp;lt; 0.05 for IIV in TIB; and B=2.74, 95% CI, 0.57, 6.19, p&amp;lt; 0.05 for IIV in risetime, respectively). There was no statistically significant association between IIV of sleep measures and excessive daytime sleepiness or mental health outcomes such as social anhedonia, depressive symptoms, and problematic alcohol use. Conclusion Greater fluctuation in TST, TIB, and risetime were negatively associated with overall sleep quality. Our findings add to a growing body of research on IIV in sleep/wake patterns and clinical implications. Future studies should explore the prospective relationship between variability in sleep and other various health outcomes. Support (if any) NIH/NIAAA R01AA025626 (Hasler); Sleep Research Society Foundation Mentor-Mentee Award (Kwon)

Variability in objective sleep is associated with Alzheimer's pathology and cognition.

Both sleep duration and sleep efficiency have been associated with risk of Alzheimer's disease, suggesting that interventions to promote optimal sleep may be a way to reduce Alzheimer's disease risk. However, studies often focus on average sleep measures, usually from self-report questionnaires, ignoring the role of intra-individual variability in sleep across nights quantified from objective sleep measures. The current cross-sectional study sought to investigate the role of intra-individual variability in accelerometer-based objective sleep duration and sleep efficiency in relation to in vivo Alzheimer's disease pathology (β-amyloid and tau) using positron emission tomography imaging and cognition (working memory, inhibitory control, verbal memory, visual memory and global cognition). To examine these relationships, we evaluated 52 older adults (age = 66.4 ± 6.89, 67% female, 27% apolipoprotein E4 carriers) with objective early mild cognitive impairment. Modifying effects of apolipoprotein E4 status were also explored. Less intra-individual variability in sleep duration was associated with lower β-amyloid burden, higher global cognition and better inhibitory control, with a trend for lower tau burden. Less intra-individual variability in sleep efficiency was associated with lower β-amyloid burden, higher global cognition and better inhibitory control, but not with tau burden. Longer sleep duration was associated with better visual memory and inhibitory control. Apolipoprotein E4 status significantly modified the association between intra-individual variability in sleep efficiency and β-amyloid burden, such that less sleep efficiency variability was associated with lower β-amyloid burden in apolipoprotein E4 carriers only. There was a significant interaction between sleep duration and apolipoprotein E4 status, suggesting that longer sleep duration is more strongly associated with lower β-amyloid burden in apolipoprotein E4 carriers relative to non-carriers. These results provide evidence that lower intra-individual variability in both sleep duration and sleep efficiency and longer mean sleep duration are associated with lower levels of β-amyloid pathology and better cognition. The relationships between sleep duration and intra-individual variability in sleep efficiency with β-amyloid burden differ by apolipoprotein E4 status, indicating that longer sleep duration and more consistent sleep efficiency may be protective against β-amyloid burden in apolipoprotein E4 carriers. Longitudinal and causal studies are needed to better understand these relationships. Future work should investigate factors contributing to intra-individual variability in sleep duration and sleep efficiency in order to inform intervention studies.

Actigraphy-measured sleep concordance, night-wakings, intraindividual sleep variability in parents and their children-Associations with childhood sleep disturbances.

The relationship between the sleep of parents and their children has primarily been studied using self-reported measures, but data using objective sleep assessments are limited. In particular, objective assessments of sleep disturbance and night-wakings in parents in relation to their children's night-wakings is underexamined. This pilot study employed actigraphy to determine concordance in sleep-wake patterns between parents and their children, and examine temporal links between their wakings lasting five min or longer. The study also explored individual variability in parents' sleep based on parent-reported sleep disturbances in children. A total of 20 parents and children (aged 2-12 years, no co-sleepers) contributed actigraphy data for the 14-night study, totalling 280 nights of data. Parents reported their sleep quality using the Pittsburgh Sleep Quality Index, and children's sleep using the Children Sleep Habits Questionnaire. Concordance analysis of actigraphy data revealed an average of 70.6% match in sleep/wake state between parents and children. Parents were three times more likely to have an awakening within 10 min of their child waking than vice versa. Parent-reported sleep disturbances in children were associated with poorer actigraphic sleep outcomes for both the parent and child. Parents of poorly sleeping children demonstrated greater variability in their bedtime, and wake after sleep onset. Further examination of temporal links between parent-child sleep can improve our understanding of factors that predispose or precipitate sleep disturbances across families. Given the high concordance in parent-child sleep and poorer actigraphy sleep outcomes in parents of children with sleep disturbances, there is a need to deliver efficacious sleep interventions at the family level.

Sleep patterns and intraindividual sleep variability in mothers and fathers at 6 months postpartum: a population-based, cross-sectional study

ObjectivesGiven that postpartum sleep is an important family process, further investigations including both mothers and fathers are necessary. The present study aimed to describe and compare sleep patterns and intraindividual...

How much does sleep vary from night-to-night? A quantitative summary of intraindividual variability in sleep by age, gender, and racial/ethnic identity across eight-pooled datasets.

Habitual sleep duration and efficiency vary widely by age, gender, and racial/ethnic identity. Despite growing research on the importance of night-to-night, intraindividual variability (IIV) in sleep, few studies have examined demographic differences in sleep IIV. The present study describes typical sleep IIV overall and by demographics among healthy sleepers. Eight datasets of healthy sleepers (N=2,404; 26,121 total days of sleep data) were synthesised to examine age, gender, and racial/ethnic identity differences in sleep IIV measured via diaries, actigraphy, and electroencephalography (EEG). Sleep IIV estimates included the intraindividual standard deviation (iSD), root mean square of successive differences (RMSSD), coefficient of variation (CV), and a validated Bayesian Variability Model (BVM). There was substantial IIV in sleep across measurement types (diary, actigraphy, EEG) for both sleep duration (iSD: 85.80 [diary], 77.41 [actigraphy], 67.04 [EEG] minutes; RMSSD: 118.91, 108.89, 91.93 minutes; CV: 19.19%, 19.11%, 18.57%; BVM: 60.60, 58.20, 48.60 minutes) and sleep efficiency (iSD: 5.18% [diary], 5.22% [actigraphy], 6.46% [EEG]; RMSSD: 7.01%, 7.08%, 8.44%; CV: 5.80%, 6.27%, 8.14%; BVM: 3.40%, 3.58%, 4.16%). Younger adults had more diary and actigraphy sleep duration IIV. Gender differences were inconsistent. White and non-Hispanic/Latinx adults had less IIV in sleep duration and efficiency compared to racial/ethnic minority groups. Even among healthy sleepers, sleep varies widely from night-to-night. Like mean sleep, there also may be disparities in IIV in sleep by demographic characteristics. Study results help characterise normative values of sleep IIV in healthy sleepers.

0242 Intraindividual Variability in Sleep Duration Blunts Response to Academic Stressors

Abstract Introduction Cross-sectional studies indicate that greater intra-individual variability (IIV) in sleep is correlated with poorer cognitive-emotional outcomes. Yet, the causal direction of these relationships is unclear. Therefore, we conducted an experimental study to compare cognitive and stress outcomes following random assignment to normal sleep, sleep restriction, and irregular/IIV sleep conditions. Methods Ninety college students (mean age=19.16, SD=0.98; 77.78% female) completed an Organic Chemistry virtual lecture during session 1. Then, for the next five days, participants were randomly assigned to the following conditions: normal sleep (8h in bed every night), sleep restriction (6h in bed every night), or IIV sleep (nightly oscillation between 6.5h and 9.5h in bed, with mean of 8h/night). Adherence was confirmed using actigraphy. On the sixth day (session 2), participants took a test on the Organic Chemistry lecture (retention measure) and then completed a new lecture and test (acquisition measure). Participants reported their stress levels across the lectures and tests. Results ANCOVA tests showed that sleep condition did not affect retention (F=0.50, p=.611) or acquisition of Organic Chemistry knowledge (F=1.33, p=.275; adjusted for Grade Point Average). Interestingly, participants in the IIV condition reported lower stress levels throughout session 2 than students in the normal sleep condition, adjusting for baseline stress levels (p=.025). Furthermore, when collapsing across conditions, correlation analyses confirmed that greater IIV in TST predicted lower stress throughout session 2, after adjusting for mean TST and baseline stress level (r=-.33, p=.014). This “blunted” stress response following nightly sleep fluctuations was in contrast to the heightened stress levels that were associated with shorter mean TST (r=-.22, p=.051). Conclusion Brief sleep variability and mild sleep restriction had minimal impact on laboratory measures of STEM knowledge retention and acquisition. However, greater sleep IIV blunted reactivity to academic stressors, which may reflect altered hypothalamic–pituitary–adrenal axis functions and have implications for student metacognition and course persistence. Future research should investigate the chronic effect of maintaining irregular sleep patterns and whether improving regularity of sleep across longer time intervals promotes cognitive and emotional functioning. Support (If Any) American Psychological Association, APAGS, Psi Chi, National Science Foundation (1920730, 1943323)

0113 Daily Patterns of Sleep and Metacognition in College Students

Abstract Introduction Sleep problems have been associated with subjective cognitive complaints (a type of metacognition) in older adults, but little research has examined if this same relationship exists in younger adults. Additionally, college students have high intra-individual variability with their sleep, making day-to-day sleep an understudied parameter of interest in this population. Considering that metacognition has been associated with academic outcomes (e.g., GPA) in college students, it is important to understand how daily sleep patterns might impact metacognition. The present study examined how intra-individual variability in sleep is associated with metacognitive ratings in college students. Methods College students (N=81, Mage=18.8, SD = 1.1, 64 females) completed seven days of sleep diaries reporting total sleep time (TST), sleep onset latency (SOL), number of nighttime awakenings, and wake after sleep onset (WASO). Students also provided morning metacognitive ratings regarding the perceived quality of mental functioning from very poor (0) to very good (100). Multilevel modeling analyses tested whether intraindividual variability in daily sleep variables was associated with daily metacognitive ratings, after controlling for interindividual sleep patterns, age, sex, sleep medication usage, and anxiety symptoms (via the Hospital Anxiety and Depression Scale). Results Daily TST was associated with metacognitive ratings (B=2.35, p=0.003), in that those who slept less than their typical average reported worse metacognitive ratings. Similarly, daily number of nighttime awakenings (B=-1.92, p=0.02) and WASO (B=-0.13, p=0.009) were also associated with metacognitive ratings, in that those with more awakenings and greater WASO than their typical average reported worse metacognitive ratings. Conclusion Findings suggest that deviation in typical daily sleep patterns (shorter TST, a greater number of nighttime awakenings, greater WASO) may impact daily metacognitive ratings in college students. Similar patterns are not observed at the average/interindividual level, prompting the need for future studies to examine daily sleep in college students. These findings point to the need for research examining whether sleep interventions (e.g., Cognitive Behavioral Therapy for Insomnia) for college students who experience sleep variability, could improve metacognition, which in turn could improve academic outcomes. Support (If Any)  

A preliminary investigation of the role of intraindividual sleep variability in substance use treatment outcomes

IntroductionPoor sleep health is common among individuals in early treatment for substance use disorders (SUDs) and may serve an important role in predicting SUD outcomes. However, sleep parameters have been inconsistently linked with risk of relapse, perhaps because previous research has focused on mean values of sleep parameters (e.g., total sleep time [TST], sleep efficiency [SE], and sleep midpoint [SM]) across multiple nights rather than night-to-night fluctuations (i.e., intraindividual variability [IIV]). The current study assessed sleep across the first week of SUD treatment, with the aim of prospectively examining the relationship between mean and IIV of TST, SE, and SM and treatment completion and relapse within one-month post-treatment. MethodsTreatment-seeking adults (N = 23, Mage = 40.1, 39% female) wore an actigraph to assess sleep for one week at the beginning of an intensive outpatient program treatment. Electronic medical record and follow-up interviews were utilized to determine treatment outcomes. ResultsGreater IIV in TST was associated with higher odds of relapse (OR = 3.55, p =.028). Greater IIV in SM was associated with lower odds of treatment completion, but only when removing mean SM from the model (OR = 0.75, p =.046). DiscussionNight-to-night variability in actigraphy-measured TST is more strongly associated with SUD treatment outcomes than average sleep patterns across the week. Integrating circadian regulation into treatment efforts to improve SUD treatment outcomes may be warranted. Given the small sample size utilized in the present study, replication of these analyses with a larger sample is warranted.

Intraindividual variability in sleep among people with insomnia and its relationship with sleep, health and lifestyle factors: an exploratory study

ObjectiveTo explore associations between intraindividual variability (IIV) in sleep patterns and sleep problems, lifestyle factors, and mental and physical health in individuals with chronic insomnia. MethodsCross-sectional study of 1720 adults with chronic insomnia (67.8% female, mean age = 44.5) who completed online self-report questionnaires and kept a sleep diary (for at least 10 out of 14 days). Linear regression analyses examined IIV in sleep patterns as independent variables, and sleep problems, lifestyle factors, and mental and physical health outcomes as dependent variables. Analysis of each sleep variable was separately adjusted for the mean value of the corresponding variable and for selected background factors. ResultsIIV in sleep variables was significantly and positively associated with scores on the Insomnia Severity Index (ISI), dysfunctional beliefs and attitudes about sleep (DBAS-16), the Chalder Fatigue Scale (CFQ), body mass index (BMI) and alcohol consumption (AUDIT-C) at study entry. The association between IIV and mental health outcomes (ie the Hospital Anxiety and Depression Scale [HADS] and subjectively reported mental health status [SF-12 Mental health]) were not significant. IIV was associated with higher (ie more positively rated) mean level of sleep quality. ConclusionIIV of sleep patterns may be a useful construct for understanding subjective experiences of sleep problems, fatigue and health in people with chronic insomnia. Our findings support notions suggesting that IIV offers additional insights beyond those offered by studying mean values alone; however, discordant findings regarding sleep quality highlight the need for further studies to examine the consequences of IIV.

Associations Between Intraindividual Variability in Sleep and Daily Positive Affect.

Recent research highlights a variety of negative outcomes associated with intraindividual variability in positive affect (PA) and in sleep. Thus, this study examined the associations of variability in multiple dimensions of sleep (quality, duration, wake after sleep onset, bedtime, rise-time) with mean and variability in PA. For 7 days, morning and evening surveys were collected online from two separate samples: community-based adults (N = 911) and university students (N = 322). Regression analyses revealed that across both samples, people with more variable sleep quality exhibited greater fluctuations in PA throughout the week and, surprisingly, higher levels of PA on average. In the community sample only, individuals with more variable sleep duration had lower and more variable PA. Findings suggest that fluctuations in sleep quality and duration are linked with daily PA outcomes, which is important to consider as technological advances and modern demands make inadequate and irregular sleep increasingly common.Supplementary InformationThe online version contains supplementary material available at 10.1007/s42761-021-00082-6.

Do self-ratings of the Pittsburgh Sleep Quality Index reflect actigraphy recordings of sleep quality or variability? An exploratory study of bipolar disorders versus healthy controls.

Sleep disturbances are typical symptoms of acute episodes of bipolar disorder (BD) and differentiate euthymic BD cases from healthy controls (HC). Researchers often employ objective recordings to evaluate sleep patterns, such as actigraphy, whilst clinicians often use subjective ratings, such as the Pittsburgh Sleep Quality Index (PSQI). As evidence suggests the measures may disagree, we decided to compare subjective (PSQI) and objective (3weeks of actigraphy) sleep profiles in BD cases and HC (n=154). We examined whether a dimensional approach helps to illustrate different patterns of sleep disturbances and whether the concordance between subjective and objective recordings varies according to clinical status (BD versus HC). Principal component analysis (PCA) extracted two factors from the PSQI, and separate PCAs of actigraphy recordings extracted two factors for mean values of sleep parameters and one factor for intra-individual variability. Correlational and linear regression analyses of PCA-derived dimensions demonstrated that, in both BD and HC, a PSQI "Sleep duration-efficiency" factor was significantly correlated with an actigraphy "Sleep initiation-duration" factor. Furthermore, in BD cases only, the PSQI total score and a PSQI "Sleep Impairments" factor were each significantly correlated with an actigraphy "Sleep Variability" factor. Overall, we found that subjective experiences of sleep may be modulated by different components of objectively recorded sleep in BD compared with HC. Also, the use of PCA enabled us to consider the multi-dimensional nature of subjective sleep, whilst the inclusion of intra-individual sleep variability afforded a more subtle evaluation of objective sleep.

The Sleep Regularity Questionnaire: development and initial validation

Background/objectiveSleep is a critically important behavior which influences diverse aspects of health, functioning, and longevity. An increasing literature suggests the importance of sleep regularity, also referred to as sleep inconsistency, sleep variability, or intraindividual variability in sleep. Given there is no brief, subjective measure of sleep regularity, the purpose of this study was to develop the Sleep Regularity Questionnaire (SRQ) and to begin the process of examining its psychometric properties using a construct-validation approach. Participants/methodsIn an online study of sleep and health, participants (n = 3249; Mage (SD) = 42.77 (16.73); 48.5% female; 77.3% white) completed the in-development SRQ, as well as the Insomnia Severity Index and the Pittsburgh Sleep Quality Index. ResultsAn exploratory factor analysis followed by a confirmatory factor analysis revealed a two factor structure, represented by circadian regularity and sleep continuity regularity, with good model fit indices (X2 = 50.9, df = 7, p < 0.001; RMSEA = 0.06; CFI = 0.99; NFI = 0.99; IFI = 0.99; TLI = 0.98). Test-retest reliability, as well as concurrent, convergent and incremental validity were examined, with promising results. ConclusionsPreliminary psychometrics suggest that the SRQ is a valid and stable instrument for the assessment of sleep regularity in adults that is related to, but distinct from, other established sleep constructs. Future research will benefit from assessing the validity of the SRQ in various clinical samples and how it compares to measures of sleep regularity calculated from prospective daily assessments.

Sleep quality and glycaemic variability in a real-life setting in adults with type 1 diabetes.

Suboptimal subjective sleep quality is very common in adults with type 1 diabetes. Reducing glycaemic variability is a key objective in this population. To date, no prior studies have examined the associations between objectively measured sleep quality and overnight glycaemic variability in adults with type 1 diabetes. We aimed to test the hypothesis that poor sleep quality would be associated with greater overnight glycaemic variability. Data were collected in the home setting from 20 adults (ten male and ten female participants) with type 1 diabetes who were current insulin pump users. Simultaneous assessments of objective sleep quality (Zmachine Insight+) and continuous glucose monitoring (CGM) were performed over multiple nights (up to 15 nights) in each participant. Due to the real-life nature of this study, the participants kept their usual CGM alerts for out-of-range glucose values. Sleep quality was categorised as 'good' or 'poor' using a composite of objective sleep features (i.e. sleep efficiency, wake after sleep onset and number of awakenings) based on the National Sleep Foundation's consensus criteria. Glycaemic variability was quantified using SD and CV of overnight glucose values based on overnight CGM profiles. A total of 170 nights were analysed. Overall, 86 (51%) nights were categorised as good sleep quality, and 84 (49%) nights were categorised as poor sleep quality. Using linear mixed-effects models, poor sleep quality was significantly associated with greater glycaemic variability as quantified by SD (coefficient: 0.39 [95% CI 0.10, 0.67], p = 0.009) and CV (coefficient: 4.35 [95% CI 0.8, 7.9], p = 0.02) of overnight glucose values, after accounting for age, sex, BMI and overnight insulin dose. There was large inter- and intra-individual variability in sleep and glycaemic characteristics. Both pooled and individual-level data revealed that the nights with poor sleep quality had larger SDs and CVs, and, conversely, the nights with good sleep quality had smaller SDs and CVs. No associations were found between sleep quality and time spent in the target glucose range, or above or below the target glucose range, where CGM alarms are most likely to occur. Objectively measured sleep quality is associated with overnight glycaemic variability in adults with type 1 diabetes. These findings highlight an important role of sleep quality in overnight glycaemic control in type 1 diabetes. They also provide a strong incentive to both patients and healthcare providers for considering sleep quality in personalised type 1 diabetes glycaemic management plans. Future studies should investigate the mechanisms linking sleep quality to glycaemic variability.

The effect of sleep-wake intraindividual variability in digital cognitive behavioral therapy for insomnia: a mediation analysis of a large-scale RCT.

Study ObjectivesDigital cognitive behavioral therapy for insomnia (dCBT-I) is an effective treatment for insomnia. However, less is known about mediators of its benefits. The aim of the present study was to test if intraindividual variability in sleep (IIV) was reduced with dCBT-I, and whether any identified reduction was a mediator of dCBT-I on insomnia severity and psychological distress.MethodsIn a two-arm randomized controlled trial (RCT), 1720 adults with insomnia (dCBT-I = 867; patient education about sleep = 853) completed the Insomnia Severity Index (ISI), the Hospital Anxiety and Depression Scale (HADS) and sleep diaries, at baseline and 9-week follow-up. Changes in IIV were analyzed using linear mixed modeling followed by mediation analyses of ISI, HADS, and IIV in singular sleep metrics and composite measures (behavioral indices (BI-Z) and sleep disturbance indices (SI-Z)).ResultsdCBT-I was associated with reduced IIV across all singular sleep metrics, with the largest between-group effect sizes observed for sleep onset latency (SOL). Reduced IIV for SOL and wake after sleep onset had the overall greatest singular mediating effect. For composite measures, SI-Z mediated change in ISI (b = −0.74; 95% confidence interval (CI) −1.04 to −0.52; 13.3%) and HADS (b = −0.40; 95% CI −0.73 to −0.18; 29.2%), while BI-Z mediated minor changes.ConclusionReductions in IIV in key sleep metrics mediate significant changes in insomnia severity and especially psychological distress when using dCBT-I. These findings offer important evidence regarding the therapeutic action of dCBT-I and may guide the future development of this intervention.Clinical trials Name: Overcoming Insomnia: Impact on Sleep, Health and Work of Online CBT-I Registration number: NCT02558647 URL: https://clinicaltrials.gov/ct2/show/NCT02558647?cond=NCT02558647&draw=2&rank=1

088 Irregular Sleep Patterns Predict Worse Sleep Quality and Poorer Psychosocial and Academic Outcomes

Abstract Introduction While the consequences of short sleep duration are well understood, relatively little is known about how irregular sleep durations are related to daily functioning. We utilized actigraphy and self-report methods to investigate the correlates of intraindividual sleep variability in two populations. Methods In Study 1, N=699 adults (mean age=38.04, SD=11.65; 44.78% female) completed online questionnaires on sleep, work status, and time management. In Study 2, N=100 college students (mean age=19.08, SD=1.26; 50% female; 50% underrepresented minorities) wore actiwatches for two one-week sessions (1 month apart) and reported sleep, psychosocial functions, and academic outcomes. In both studies, variability of sleep duration was defined as the individual standard deviation (ISD) of sleep durations. Results In Study 1, after controlling for mean sleep duration, greater variability in sleep duration was related to shiftwork (F=8.68, p=.003), younger age (r=-.15, p&amp;lt;.001), male gender (F=4.43, p=.036), and greater vulnerability to stress (r=.15, p=.001). Beyond mean sleep duration, variability in sleep duration also predicted poorer sleep quality (r=.25, p&amp;lt;.001), greater sleepiness during the day (r=.10, p=.014), poorer time management (r=-.09, p=.031), lower work efficiency (r=-.14, p=.002), and more procrastination (r=.11, p=.009). In Study 2, variability in actigraphy-defined sleep duration increased as the semester progressed (ISD=1.25±0.55 hours at T1; ISD=1.57±0.80 hours at T2, t=4.64, p&amp;lt;.001). After controlling for mean sleep duration, sleep variability was associated with greater perceived stress (r=.31, p=.002 at T1), poorer sleep quality (r=.39, p&amp;lt;.001 at T1; r=.30, p=.003 at T2), and lower expected grades (r=-.27, p=.01 at T2). Sleep variability was unrelated to depression or perceptions of one’s overall health. Conclusion Keeping regular sleep habits appear just as important as average sleep duration to psychosocial, work, and academic outcomes. Sleep interventions should incorporate specific guidelines on how to promote regular sleep and employers should institute work schedules that promote regularity. Support (if any) This work is supported by the National Science Foundation, Psi Chi Honor Society, and the American Psychological Association.