Irregular sleep is linked to poorer mental health: A pooled analysis of eight studies

OBJECTIVES

Greater sleep disturbances on average are a risk factor for impaired mental health. Recent research has shown that more intraindividual variability (i.e., inconsistency) in sleep (hereafter called "sleep intraindividual variability") may also be uniquely related to mental health, even above the influence of mean sleep patterns averaged across days. The current study examined associations between sleep intraindividual variability and symptoms of anxiety, depression, and insomnia across different facets of sleep intraindividual variability (sleep duration, efficiency, and timing) and sleep measurement types (sleep diary and actigraphy).

METHODS

We pooled eight datasets (N = 3053 participants) that assessed repeated measures of sleep diary- and/or actigraphy-determined sleep across multiple days, as well as one-time measures of mental health or sleep disorder symptoms (i.e., anxiety, depression, and insomnia). Multilevel regression analyses were conducted to examine associations between sleep intraindividual variability and mental health or sleep disorder symptoms.

RESULTS

Greater diary- and actigraphy-determined sleep duration intraindividual variability was associated with more depression symptoms (diary: b=0.02, p < .001; actigraphy: b=0.03, p = .006) and more insomnia symptoms (diary: b=0.02, p < .001; actigraphy: b=0.02, p < .001). Greater diary-determined sleep efficiency intraindividual variability was associated with fewer anxiety symptoms (b=-0.23, p = .019) and fewer insomnia symptoms (b=-0.15, p < .001). Greater diary- and actigraphy-determined sleep midpoint intraindividual variability was associated with more insomnia symptoms (diary: b=0.41, p = .044; actigraphy: b=0.66, p = .021).

CONCLUSIONS

More inconsistent sleep duration and sleep timing may be a correlate of poorer mental health. Future experimental work should examine whether stabilizing sleep patterns can improve mental health outcomes.

Preserving What Matters: Longitudinal Changes in Control Over Interpersonal Stress and Noninterpersonal Stress in Daily Life

OBJECTIVES

Theoretical perspectives on aging suggest that when people experience declines in later life, they often selectively focus on maintaining aspects of their lives that are most meaningful and important to them. The social domain is one of these selected areas. The current study examines people's reports of control over their daily stressors over 10 years, predicting that the declines in control that are often observed in later life will not be observed for stressors involving interpersonal conflict and tensions with social partners.

METHODS

Adults ranging from 35 to 86 years old at baseline (N = 1,940), from the National Study of Daily Experiences, reported control over interpersonal and noninterpersonal daily stressors across 8 consecutive days at 2 time points, about 10 years apart.

RESULTS

Findings from multilevel models indicate that for noninterpersonal stressors, perceived control decreased over time. In contrast, perceived control over interpersonal conflicts and tensions remained robust over time. No cross-sectional baseline age differences were found for levels of interpersonal and noninterpersonal stressor control.

DISCUSSION

Results are consistent with socioemotional selectivity and underscore the importance of interpersonal relationships in later adulthood. Understanding how people select and preserve certain aspects of control in their daily life can help guide efforts toward maximizing gains and minimizing losses in domains that matter most to people as they grow older.

Parent Anxiety, Depression, Protective Responses, and Parenting Stress in the Context of Parent and Child Chronic Pain: A Daily Diary Study of Parent Variability

Parents with (vs without) chronic pain report poorer psychosocial functioning (eg, worse mental health, parenting difficulties), which has been linked to poorer child outcomes (eg, child pain). However, emerging research suggests that individuals vary in their functioning from day-to-day, particularly those with chronic pain. This study used daily diaries to compare parents with (versus without) chronic pain on variability in their anxiety, mood, protective responses, and parenting stress. We also examined parent chronic pain status as a moderator of the associations between parent variability and youth daily pain and interference. Participants were 76 youth with chronic pain (Mage = 14.26; 71.1% female) and one of their parents (89.5% mothers; n = 38 or 50.0% endorsing chronic pain). Parents and youth completed self-report questionnaires and 7 days of diaries. Parent variability was calculated to reflect the frequency and size of day-to-day changes. Multilevel models revealed that parents with (vs without) chronic pain were significantly more variable in their parenting stress, but not in their anxiety, mood, or protective responses. Contrary to hypotheses, parent variability was not significantly related to youth daily pain intensity or interference and parent chronic pain did not moderate any associations. Instead, mean levels of parent anxiety, protective responses, and parenting stress across the week significantly predicted youth daily pain interference. Findings suggest that while variability was observed among parents (with and without chronic pain) of youth with chronic pain, it did not significantly predict youth's daily pain-related functioning. Further research is needed to confirm these initial findings. PERSPECTIVE: Parents with chronic pain have expressed concerns that the variable nature of their pain negatively impacts their children. Our results found that parents (with and without chronic pain) were variable in their anxiety, mood, protective responses, and parenting stress, but this variability did not significantly predict youth's chronic pain-related functioning.

Beyond the mean: examining associations between intraindividual variability in posttraumatic stress disorder symptoms and posttrauma reckless behaviors

BACKGROUND/OBJECTIVES

Posttrauma reckless behaviors have been linked to the onset and exacerbation of posttraumatic stress disorder (PTSD) symptoms. However, PTSD symptoms fluctuate across time, triggered by environmental stimuli in daily life, referred to as (intraindividual) variability in PTSD symptoms.

DESIGN

We utilized experience sampling methods to investigate associations between engagement in posttrauma reckless behaviors and variability in PTSD symptoms and the moderating role of emotion dysregulation in this association.

METHODS

Data from 166 trauma-exposed university students (Mage = 21.43 ± 5.07, 85.4% women) were collected between January 2019 to August 2020. Participants completed baseline and follow-up surveys to assess engagement in posttrauma reckless behaviors and daily surveys (10-days) to assess variability in PTSD symptoms. Results. Analyzes indicated greater baseline engagement in posttrauma reckless behaviors was associated with greater 10-day variability in PTSD symptoms (β = 0.23, p = .031), and baseline emotion dysregulation moderated this association (β = -0.33, p = .003). Additionally, greater 10-day variability in PTSD symptoms was associated with greater follow-up engagement in posttrauma reckless behaviors (β = 0.14, p = .045).

CONCLUSIONS

Findings substantiate the interplay between engagement in posttrauma reckless behaviors and daily fluctuations in PTSD symptoms and support therapeutically targeting both engagement in posttrauma reckless behaviors and emotion dysregulation to impact PTSD symptoms.

Beyond the Global Brain Differences: Intraindividual Variability Differences in 1q21.1 Distal and 15q11.2 BP1-BP2 Deletion Carriers

BACKGROUND

Carriers of the 1q21.1 distal and 15q11.2 BP1-BP2 copy number variants exhibit regional and global brain differences compared with noncarriers. However, interpreting regional differences is challenging if a global difference drives the regional brain differences. Intraindividual variability measures can be used to test for regional differences beyond global differences in brain structure.

METHODS

Magnetic resonance imaging data were used to obtain regional brain values for 1q21.1 distal deletion (n = 30) and duplication (n = 27) and 15q11.2 BP1-BP2 deletion (n = 170) and duplication (n = 243) carriers and matched noncarriers (n = 2350). Regional intra-deviation scores, i.e., the standardized difference between an individual's regional difference and global difference, were used to test for regional differences that diverge from the global difference.

RESULTS

For the 1q21.1 distal deletion carriers, cortical surface area for regions in the medial visual cortex, posterior cingulate, and temporal pole differed less and regions in the prefrontal and superior temporal cortex differed more than the global difference in cortical surface area. For the 15q11.2 BP1-BP2 deletion carriers, cortical thickness in regions in the medial visual cortex, auditory cortex, and temporal pole differed less and the prefrontal and somatosensory cortex differed more than the global difference in cortical thickness.

CONCLUSIONS

We find evidence for regional effects beyond differences in global brain measures in 1q21.1 distal and 15q11.2 BP1-BP2 copy number variants. The results provide new insight into brain profiling of the 1q21.1 distal and 15q11.2 BP1-BP2 copy number variants, with the potential to increase understanding of the mechanisms involved in altered neurodevelopment.

The Affective Dynamics of Everyday Digital Life: Opening Computational Possibility

Up to now, there was no way to observe and track the affective impacts of the massive amount of complex visual stimuli that people encounter "in the wild" during their many hours of digital life. In this paper, we propose and illustrate how recent advances in AI-trained ensembles of deep neural networks-can be deployed on new data streams that are long sequences of screenshots of study participants' smartphones obtained unobtrusively during everyday life. We obtained affective valence and arousal ratings of hundreds of images drawn from existing picture repositories often used in psychological studies, and a new screenshot repository chronicling individuals' everyday digital life from both N = 832 adults and an affect computation model (Parry & Vuong, 2021). Results and analysis suggest that (a) our sample rates images similarly to other samples used in psychological studies, (b) the affect computation model is able to assign valence and arousal ratings similarly to humans, and (c) the resulting computational pipeline can be deployed at scale to obtain detailed maps of the affective space individuals travel through on their smartphones. Leveraging innovative methods for tracking the emotional content individuals encounter on their smartphones, we open the possibility for large-scale studies of how the affective dynamics of everyday digital life shape individuals' moment-to-moment experiences and well-being.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42761-023-00202-4.

Differences in sleep patterns between patients with anorexia nervosa and healthy controls: a cross-sectional study

BACKGROUND

Sleep difficulties are common in patients with anorexia nervosa (AN), but objective assessments have mostly been performed in hospital and laboratory settings. We aimed to identify differences in sleep patterns between patients with AN and healthy controls (HC) in their free-living environments, and potential associations between sleep patterns and clinical symptoms in patients with AN.

METHODS

This cross-sectional study analyzed 20 patients with AN prior to them starting outpatient treatment and 23 HC. Sleep patterns were measured objectively using an accelerometer (Philips Actiwatch 2) for 7 consecutive days. Average sleep onset, sleep offset, total sleep time, sleep efficiency, wake after sleep onset (WASO) and mid-sleep awakenings lasting ≥ 5 min were compared between patients with AN and HC using nonparametric statistical analyses. Associations of sleep patterns with body mass index, eating-disorder symptoms, eating-disorder-associated impairment, and symptoms of depression were assessed in the patient group.

RESULTS

Compared with HC, patients with AN had shorter WASO [median (interquartile range(IQR)): 33 vs. 42 min], but a longer average duration of mid-sleep awakenings lasting ≥ 5 min [median (IQR): 9 vs. 6 min, p = 0.006] and had more nights with no sleep (six nights in four patients with AN vs. zero nights in HC). There were no differences between patients with AN and HC regarding other sleep parameters and no significant correlations between sleep patterns and clinical parameters in patients with AN. However, HC presented a Intraindividual variability pattern that was closer to a normal distribution, whereas patients with AN tended to either have very regular or large variability in sleep onset time (AN; n = 7 < 25th percentile and n = 8 > 75th percentile vs. HC; n = 4 < 25 percentile and n = 3 > 75th percentile) during the week of sleep recordings.

CONCLUSION

Patients with AN seem to spend more time awake during the night and have more nights without sleep than do HC, even though their average weekly sleep duration did not differ from that in HC. The intraindividual variability in sleep pattern seems to be an important parameter that should be assessed when studying sleep in patients with AN. Trial registration ClinicalTroals.gov. Identifier: NCT02745067. Registered: April 20, 2016.

Intraindividual variability in brain activation-A novel correlate of obesity risk among female college students

There are published data describing impairments in the brain function of adolescents or young adults who have a genetic or familial predisposition for obesity. From these descriptions, it is often assumed that the impairments are appropriately captured by a central tendency estimate and therefore consistently detectable. The present study questions this assumption and shows that the variability in brain function over the time course of a cognitive task is a better predictor of familial risk than its central tendency. Sixty-nine female young adults lacking an obese parent and 24 female young adults with an obese parent were compared on the average amplitude and inter-trial variability (ITV) in amplitude of their P300 electroencephalographic responses to rarely-occurring stimuli during a selective attention task. Simple group comparisons revealed statistically significant findings with effect sizes that were markedly greater for analyses of P300 ITV versus P300 average amplitude. It is suggested that the elevation in P300 ITV among young adults with familial risk indicates temporal instability in systems responsible for the maintenance of attention. These fluctuations may episodically disrupt their attention to satiety cues as well as other cues that influence behavior regulation.

Examining the role of attentional allocation in working memory precision with pupillometry in children and adults

Working memory (WM) precision, or the fidelity with which items can be remembered, is an important aspect of WM capacity that increases over childhood. Why individuals are more or less precise from moment to moment and why WM becomes more stable with age are not yet fully understood. Here, we examined the role of attentional allocation in visual WM precision in children aged 8 to 13 years and young adults aged 18 to 27 years, as measured by fluctuations in pupil dilation during stimulus encoding and maintenance. Using mixed models, we examined intraindividual links between change in pupil diameter and WM precision across trials and the role of developmental differences in these associations. Through probabilistic modeling of error distributions and the inclusion of a visuomotor control task, we isolated mnemonic precision from other cognitive processes. We found an age-related increase in mnemonic precision that was independent of guessing behavior, serial position effects, fatigue or loss of motivation across the experiment, and visuomotor processes. Trial-by-trial analyses showed that trials with smaller changes in pupil diameter during encoding and maintenance predicted more precise responses than trials with larger changes in pupil diameter within individuals. At encoding, this relationship was stronger for older participants. Furthermore, the pupil-performance coupling grew across the delay period-particularly or exclusively for adults. These results suggest a functional link between pupil fluctuations and WM precision that grows over development; visual details may be stored more faithfully when attention is allocated efficiently to a sequence of objects at encoding and throughout a delay period.

Altered brain activation in uncomplicated pediatric obesity: The second moment is more sensitive than the first

Traditionally, studies of the neurocognitive correlates of obesity have computed a central tendency across trials of a task to estimate the functional abilities of individual members of obese and non-obese groups. This computation assumes that the correlate is stable over time-a questionable assumption when individuals are impulsive, periodically inattentive, and capable of overcompensation following awareness of failure. The present investigation departs from the tradition by focusing on the second moment, or variability, in brain activation during a simple selective attention task. It compared 124 non-obese and 80 obese teenaged girls on the across-trial average amplitude and inter-trial variability (ITV) of a sensitive biomarker of attention, the P300 event-related electroencephalographic potential. It found that P300 ITV outperformed P300 average amplitude in differentiating the groups. Further, it found that the elevated P300 ITV among obese teenagers was associated with other indicators of impulsivity and inattention as well as slower reaction times and a trend toward more variable reaction times. Future studies should investigate the value of P300 ITV as an objective and sensitive endpoint for cognitive training focused on improving the attention skills of obese children.

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

INTRODUCTION

Poor 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.

METHODS

Treatment-seeking adults (N = 23, M_age = 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.

RESULTS

Greater 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).

DISCUSSION

Night-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.

Deviations from typical paths: a novel approach to working with GPS data in the behavioral sciences

Background

Behavioral science researchers are increasingly collecting detailed location data such as second-by-second GPS tracking on participants due to increased ease and affordability. While intraindividual variability has been discussed in the travel literature for decades, traditional methods designed for studying individual differences in central tendencies limit the extent to which novel questions about variability in lived experiences can be answered. Thus, new methods of quantifying behavior that focus on intraindividual variability are needed to address the context in which the behavior occurs and the location tracking data from which behavior is derived.

Methods

We propose deviations from typical paths as a data processing technique to separate individual-level typical travel behavior from a location tracking data set in order to highlight atypical travel behavior as an outcome measure.

Results

A simulated data example shows how the method works to produce deviation measures from a location dataset. Analysis of these deviations offers additional insights compared to traditional measures of maximum daily distance from home.

Conclusions

This process can be integrated into larger research questions to explore predictors of atypical behavior and potential mechanisms of behavior change.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12942-022-00305-4.

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

OBJECTIVE

To explore associations between intraindividual variability (IIV) in sleep patterns and sleep problems, lifestyle factors, and mental and physical health in individuals with chronic insomnia.

METHODS

Cross-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.

RESULTS

IIV 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.

CONCLUSION

IIV 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.

Predator-prey population dynamics may induce the evolutionary dynamics of behavioral unpredictability

Behavioral unpredictability (within-individual behavioral variability that cannot be explained by extrinsic and intrinsic factors) has been observed in a wide variety of species, but its adaptive significance is not well understood. This study examines the possibility that behavioral unpredictability is maintained through predator-prey population dynamics. An individual-based model was constructed to track the status of individual predators. The handling time of a predator is characterized by its expected value and unpredictability, which are heritable, and each predator features a unique combination of these characteristics. A discrete generation model in which one prey species and one predator species interact was constructed. The model showed that the evolutionarily stable strategy (ESS) of handling time is associated with no behavioral unpredictability and that the ESS handling time depends on the densities of the prey and predators. When populations exhibit cyclic dynamics, the ESS also changes along with the population dynamics, thereby creating mismatches between the traits of predators and the ESS because the dynamics of the ESS and population are faster than the evolution of the handling time traits. This mismatch can generate conditions in which individuals with behavioral unpredictability are at least transiently selected because of the topology of the fitness landscape. However, the model also showed that the selection strength of behavioral unpredictability is weak and can be overruled by inherent stochastic processes.

Temporal instability in brain activation: a novel paradigm for evaluating the maintenance of attention among substance dependent patients

RATIONALE

Prior studies have demonstrated statistically significant but subtle differences in brain function between patients with a history of substance dependence (SD) and control groups.

OBJECTIVES

The goal of the present study was to show that variability in brain activation over the trials of a cognitive task is more useful for revealing the putative impact of SD than analyses focusing on the amplitude of activation averaged over trials. The study also tested the additional contribution of antisocial personality disorder (ASPD)-a prevalent comorbidity that promotes both an early onset and more severe course of SD.

METHODS

Two hundred eleven adults performed two selective attention tasks while P300 event-related electroencephalographic potentials were recorded. They were assigned to one of 3 mutually exclusive groups: no lifetime history of SD or ASPD (n = 67), a SD history but no ASPD (n = 68), or both SD and ASPD (n = 76).

RESULTS

The major finding was a statistically significant elevation of P300 amplitude inter-trial variability (ITV) in the SD plus ASPD group in comparison to the group with neither attribute. The elevation was detected during both selective attention tasks and most prominent at electrodes sites located over the frontal brain. There were no group differences in P300 amplitude averaged over trials.

CONCLUSIONS

We conclude from these findings that the ITV of P300 amplitude is an efficient and sensitive biomarker of the maintenance of attention. It is valuable for revealing group differences associated with substance dependence and ASPD. It may ultimately be valuable for detecting improvements resulting from psychostimulant treatment or other interventions, including cognitive remediation.

Women's Self-Relevant Goal Pursuit in the Presence of Physical Pain: An Intraindividual Variability Approach

OBJECTIVES

Pursuing personal goals that are relevant to one's sense of self is important for adjusting to age-related changes. Experiences of physical pain, however, are thought to threaten both people's sense of self and their pursuit of personal goals. Although a majority of older women experience physical pain, little is known about their day-to-day regulation of their self-relevant goals in the presence of physical pain. The objectives of this study were to explore associations between physical pain and health goal pursuit on a daily basis for women who identified health as a part of their possible selves.

METHODS

We took an intraindividual variability approach to analyze whether there were within- and between-person differences in associations between daily pain and daily health goal progress among 62 women who provided data over the course of 100 days, yielding 4,150 occasions of data.

RESULTS

At the between-person level, women with higher pain on average had lower health goal pursuit on average. At the within-person level, days of higher-than-average pain were associated with lower same-day health goal progress.

DISCUSSION

Our results suggest that pain interrupts regulation of a self-relevant goal at a within-person-not just between-person-daily level. Future work should consider how these daily, within-person, disruptions affect broader identity processes and overall well-being.

The Sleep Regularity Questionnaire: development and initial validation

BACKGROUND/OBJECTIVE

Sleep 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/METHODS

In an online study of sleep and health, participants (n = 3249; M_age (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.

RESULTS

An 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.

CONCLUSIONS

Preliminary 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.

Variable objective sleep quality is related to worse spatial learning and memory in young adults

OBJECTIVE

The majority of research on sleep and cognition has focused on mean markers of sleep across multiple nights; however, variable sleep patterns have become increasingly common in the modern era. The purpose of this study was to examine whether objective intraindividual variability in sleep quantity and quality are related to verbal and visuospatial learning and memory functioning in young adults.

METHODS

A total of 218 young adult college students were recruited from a university in the Eastern United States, among which 187 participants (70.6% female; mean age = 20.5, SD = 1.5) had complete actigraphy and cognitive performance data. Objective intraindividual means and variabilities of sleep quantity (total sleep time) and sleep quality (percent wake after sleep onset) were measured over a 1- to 2-week timeframe using wrist actigraphy. Verbal and visuospatial learning and memory were assessed using the International Shopping List and Groton Maze Learning tests of the Cogstate computerized test battery.

RESULTS

Greater intraindividual variability in actigraphy-derived sleep quality was associated with poorer visuospatial learning and memory performance after controlling for mean sleep quality and visuomotor attention and processing speed (ps < 0.05). Actigraphic measures of sleep quantity were not related to any learning and memory measures.

CONCLUSION

In young adults, intraindividual variability in objective sleep quality was significantly related to visuospatial learning and memory, over and above mean sleep quality. Given these associations, future studies should aim to identify modifiable lifestyle and environmental factors contributing to variable sleep quality.

Mean Levels and Variability in Psychological Well-Being and Associations With Sleep in Midlife and Older Women

BACKGROUND

Disturbed sleep is prevalent in older adulthood and particularly among women. Greater psychological well-being (PWB) is associated with better sleep, but intraindividual variability in PWB has not been examined.

PURPOSE

The current study examined whether mean levels and variability in PWB were associated with sleep disturbances in midlife and older women.

METHODS

Participants (N = 189) completed up to seven daily diaries and an end of the week assessment every 3 months for nine waves. Participants answered questions about their nightly sleep disturbances and reported their PWB using Ryff's six dimensions of PWB.

RESULTS

Regression models indicated that greater variability in one aspect of PWB, positive relations with others, was related to greater sleep disturbance even after adjusting for mean levels of well-being. Greater variability in environmental mastery, purpose in life, and self-acceptance were also associated with sleep disturbance, but these associations were no longer significant after adjusting for mean levels of well-being.

CONCLUSIONS

Results suggest that fluctuations in positive relations with others are related to sleep in adult women above and beyond mean levels of well-being. Results highlight the importance of considering variability in addition to mean levels of PWB.

Variability of Sleep and Relations to Body Weight Among First-Year College Students

BACKGROUND

Existing research suggests that greater sleep variability may increase risk for weight gain. College often marks a transition to a less consistent daily schedule, which may adversely impact sleep routines and further increase risk for weight gain. The current study is among the first to explore relations between nighttime sleep variability and daytime sleep (napping) and body weight among first-year college students.

METHODS

Using daily diary methods, first-year college students (N = 307; 84.7% female) self-reported their sleep for seven days. Several indices were created to capture sleep variability for reported bedtime, wake time, and sleep duration, including weekday versus weekend differences (WvW), day to day differences (D2D), and overall standard deviation (SD). Napping was also assessed. Based on body mass index (BMI), individuals were categorized as underweight, healthy weight, overweight, and obese.

RESULTS

Across indices, students' sleep varied over an hour on average across the week. Hierarchical regressions revealed that greater differences in wake time D2D, wake time SD, and sleep duration WvW were all associated with higher BMI, after accounting for gender, depressive symptoms, and sleep duration. Longer napping was also associated with higher BMI, using the same covariates. Finally, greater sleep variability was reported by overweight and obese than healthy weight individuals.

CONCLUSION

These findings suggest that sleep variability, particularly wake times and napping may be important modifiable sleep behaviors to investigate in future studies. More longitudinal research is needed to explore relations between multiple facets of sleep variability and weight gain, including possible mechanisms.

Behavioral and cognitive correlates of the aperiodic (1/f-like) exponent of the EEG power spectrum in adolescents with and without ADHD

Efficient information processing facilitates cognition and may be disrupted in a number of neurodevelopmental conditions. And yet, the role of inefficient information processing and its neural underpinnings remains poorly understood. In the current study, we examined the cognitive and behavioral correlates of the aperiodic exponent of the electroencephalogram (EEG) power spectrum, a putative marker of disrupted, inefficient neural communication, in a sample of adolescents with and without ADHD (n = 184 nADHD = 87; Mage = 13.95 years, SD = 1.36). Exponents were calculated via FOOOF (Donoghue et al., 2020a) from EEG data recorded during an 8-minute baseline episode. Reaction time speed and variability, as well as drift diffusion parameters (including the drift rate parameter, a cognitive parameter directly related to inefficient information processing) were calculated. Adolescents with ADHD had smaller aperiodic exponents (a "flattened" EEG power spectrum) relative to their typically-developing peers. After controlling for ADHD, aperiodic exponents were related to reaction time variability and the drift rate parameter, but not in the expected direction. Our findings lend support for the aperiodic exponent as a neural correlate of disrupted information processing, and provide insight into the role of cortical excitation/inhibition imbalance in the pathophysiology of ADHD.

Using Cognitive Intraindividual Variability to Measure Intervention Effectiveness: Results from the Baltimore Experience Corps Trial

OBJECTIVES

Studies investigating the effectiveness of intervention programs on cognitive ability in older adults are inconsistent; however, these studies generally focus on traditional measures of cognition, and therefore may miss some improvements by not utilizing alternate measures. We evaluate the potential for intraindividual variability in cognitive speed (IIV), a demonstrated sensitive indicator of cognitive functioning, to be used as an index of cognitive plasticity from an intervention. The current study evaluated whether older adults in a school volunteering program showed a reduction in IIV, compared to a low-activity control group over 2 years of exposure.

METHOD

Nondemented older adults (n = 336) participated in the Baltimore Experience Corps Trial, an evaluation of a volunteering program conducted at elementary schools designed to increase older adults' physical, cognitive, and social engagement. Participants completed a cognitive battery that included a Stroop task at baseline and after 12 and 24 months.

RESULTS

Traditional intent-to-treat analyses did not report significant improvements. Participants who complied at the 80th percentile or above showed a significant reduction in IIV at 24 months, with an additional trend of improved IIV with increased compliance to the treatment protocol, both at 12 months, and at 24 months. Men also showed dose-dependent improvements after 12 months.

DISCUSSION

The Experience Corps program resulted in an improvement in cognitive performance as measured by IIV. Analyzing previously collected data with nontraditional measures of cognition, such as IIV, may be a potentially fruitful and cost-effective method for understanding how interventions impact cognition in aging populations.

Predicting Control Beliefs in Older Adults: A Micro-Longitudinal Study

OBJECTIVES

The present study examined potential sources of intra- and inter-individual differences in older adults' control beliefs using a micro-longitudinal design.

METHOD

Older adults (n = 205) ranging in age from 60 to 94 (M = 72.70, SD = 6.72) completed 8 in-person testing sessions within 3 weeks which included assessments of control beliefs (Locus of Control and Perceived Competence), physical health (physical symptoms and sleep self-efficacy), stressors, emotional well-being (Positive Affect and Negative Affect), and cognition (basic cognition tests, everyday cognition, and memory failures).

RESULTS

Multilevel models indicated that on days when older adults had higher sleep self-efficacy, more positive affect, and less negative affect, they also had more internal locus of control and higher perceived competence. Having stressors on the previous occasion was associated with lower internal locus of control on the subsequent occasion. Physical symptoms, everyday cognition, and memory failures could be predictive of locus of control for some older adults.

DISCUSSION

Our findings showed the differentiated antecedents of locus of control and perceived competence, the unique role of sleep self-efficacy, positive affect, and negative affect in understanding antecedents of both, as well as the need to study well-being and cognition antecedents of control beliefs in future studies.

Feeling Young and in Control: Daily Control Beliefs Are Associated With Younger Subjective Ages

OBJECTIVES

Daily variations in control beliefs are associated with developmental outcomes. We predicted that on days when older adults feel more in control than their personal average, they would also report feeling younger, and explored the relationship in younger adults.

METHOD

A total of 116 older and 107 younger adults completed a 9-day daily diary study. On Day 1 participants reported on demographic variables. On Days 2-9, participants reported their daily subjective age, daily control beliefs, daily stressors, and daily physical health symptoms. All measures were completed online via Qualtrics. Results were analyzed using multilevel models.

RESULTS

Controlling for age, gender, education, daily stressors, daily physical health, and average control, there was a significant main effect of daily control beliefs on daily subjective age. Older adults felt significantly younger on days with a greater sense of control than usual, but this effect was absent in younger adults. For younger adults, average exposure to daily stressors and daily fluctuations in physical health were better predictors of daily subjective age.

DISCUSSION

These findings suggest that higher daily control is associated with younger subjective ages in older adults, whereas other factors may play a more central role in the daily variations of younger adults' subjective ages.

Daily Stress Reactivity Across the Life span: Longitudinal and Cross-Sectional Effects of Age

OBJECTIVE

Exploration of development requires the use of research designs and process-oriented methodologies that can capture daily fluctuations within individuals, systematic changes within individuals, and differences between individuals. We examine the stress-affect relationship in this way to assess how the relationship between daily stress and negative affect (NA) as well as the relationship between daily stress and positive affect (PA) differs between individuals and changes over time depending on age and stress differences.

METHOD

Participants (N = 966) completed daily "burst" assessments of stress, NA, and PA. Three-level multilevel models depicted how cross-sectional age, within-person age changes, and global stress differences impact the daily stress-affect relationship.

RESULTS

Findings illustrate that cross-sectional age and the aging process uniquely buffer the stress-NA relationship whereas global stress exacerbates it. Furthermore, older adults as well as adults with low global stress experience a weaker relationship between daily stress and PA as they age, but midlife adults and adults with high global stress experience a stronger relationship.

DISCUSSION

These results depict differences in aging trajectories for both midlife and older adults and thus inform intervention and preventative care strategies aimed toward promoting stress regulation.

Short-Term Disability Fluctuations in Late Life

OBJECTIVES

Late-life disability is highly dynamic but within-person short-term fluctuations have not been assessed previously. We analyze how substantial such late-life disability fluctuations are and whether they are associated with time-to-death, long-term disability trajectories, frailty, and sociodemographics.

METHODS

Monthly survey data (Precipitating Events Project Study) on activities of daily living/instrumental activities of daily living (ADL/IADL) disability (0-9) in the last years of life from 642 deceased respondents providing 56,308 observations were analyzed with a two-step approach. Observation-level residuals extracted from a Poisson mixed regression model (first step), which depict vertical short-term fluctuations from individual long-term trajectories, were analyzed with a linear mixed regression model (second step).

RESULTS

Short-term disability fluctuations amounted to about one ADL/IADL limitation, increased in the last 4 years of life, and were closely associated with disability increases. Associations with frailty or sociodemographics characteristics were absent except for living alone.

DISCUSSION

Short-term disability fluctuations in late life were substantial, were linked to mortality-related processes, and represent a concomitant feature of disability increases in late life.

Within-person structures of daily cognitive performance differ from between-person structures of cognitive abilities

Over a century of research on between-person differences has resulted in the consensus that human cognitive abilities are hierarchically organized, with a general factor, termed general intelligence or “g,” uppermost. Surprisingly, it is unknown whether this body of evidence is informative about how cognition is structured within individuals. Using data from 101 young adults performing nine cognitive tasks on 100 occasions distributed over six months, we find that the structures of individuals’ cognitive abilities vary among each other, and deviate greatly from the modal between-person structure. Working memory contributes the largest share of common variance to both between- and within-person structures, but the g factor is much less prominent within than between persons. We conclude that between-person structures of cognitive abilities cannot serve as a surrogate for within-person structures. To reveal the development and organization of human intelligence, individuals need to be studied over time.

Beyond Measures of Central Tendency: Novel Methods to Examine Sex Differences in Neuropsychological Performance Following Sports-Related Concussion in Collegiate Athletes

OBJECTIVE

The purpose of this study was to examine sex differences in neuropsychological functioning after sports-related concussion using several approaches to assess cognition: mean performance, number of impaired scores, and intraindividual variability (IIV).

METHOD

In the study, 152 concussed college athletes were administered a battery of neuropsychological tests, on average, 10 days post-concussion (SD = 12.75; Mdn = 4 days; Range = 0-72 days). Mean performance was evaluated across 18 individual neuropsychological variables, and the total number of impaired test scores (>1.5 SD below the mean) was calculated for each athlete. Two measures of IIV were also computed: an intraindividual standard deviation (ISD) score and a maximum discrepancy (MD) score.

RESULTS

Analyses of covariance revealed that, compared with males, females had significantly more impaired scores and showed greater variability on both IIV indices (ISD and MD scores) after adjusting for time since injury and post-concussive symptoms. In contrast, no significant effects of sex were found when examining mean neuropsychological performance.

CONCLUSION

Although females and males demonstrated similar mean performance following concussion, females exhibited a greater level of cognitive impairment and larger inconsistencies in cognitive performance than males. These results suggest that evaluating cognitive indices beyond mean neuropsychological scores may provide valuable information when determining the extent of post-concussion cognitive dysfunction.

Intraindividual variability in sleep and perceived stress in young adults

OBJECTIVES

Research suggests strong associations between habitual sleep parameters (eg, mean duration, timing, efficiency), perceived stress, and insomnia symptoms. The associations between intraindividual variability (IIV; night-to-night within-person variation) in sleep, perceived stress, and insomnia have not been explored. This study examined associations between IIV in subjectively and objectively determined sleep parameters and to perceived stress in young adults with and without insomnia.

DESIGN

Prospective longitudinal.

SETTING AND PARTICIPANTS

Participants were 149 college students (mean age = 20.2 [SD = 2.4], 59% female) either with insomnia (n = 81; 54%) or without insomnia (n = 68; 46%).

MEASUREMENTS

Participants completed 1 week of daily sleep diaries and actigraphy (to assess total sleep time [TST], sleep efficiency [SE], and circadian midpoint [CM]), the Perceived Stress Scale, and a diagnostic interview for determination of insomnia as part of a parent study.

RESULTS

Greater IIV in actigraphy-determined TST (but not SE or CM) was independently associated with greater perceived stress, regardless of insomnia status. Greater IIV in sleep diary-determined TST, SE, or CM was not associated with perceived stress. Insomnia status was the most robust predictor of elevated perceived stress. There was a significant interaction between IIV in sleep diary-determined TST and insomnia status on perceived stress: Only in those without insomnia was greater IIV in sleep diary-determined TST associated with higher perceived stress.

CONCLUSION

Maintaining a more consistent sleep duration may be associated with lower stress in college students. Future research is needed to clarify the directionality and implications of this association for treatment.

The Impact of a Sustained Cognitive Engagement Intervention on Cognitive Variability: The Synapse Project

Background

Interest in maintaining one's cognitive ability and quality of life through older adulthood has greatly increased in recent years. However, research examining the effectiveness of cognitive engagement interventions on older adults is mixed and the mechanisms behind improving cognition in older age are unknown. It is possible that traditional measures of cognitive outcomes, such as average reaction time, may overlook potential benefits due to a lack of sensitivity in these measures. One alternative metric is intraindividual variability (IIV) in response speed (short-term variations in performance on reaction time tasks), which reflects fluctuations in attention and is a sensitive behavioral measure of neurological integrity that is predictive of future cognitive decline and impairment.

Objective

The current study aimed to investigate whether IIV was improved in older adults through productive cognitive engagement (i.e., acquisition of new skills) in comparison to receptive engagement (activities that rely upon existing knowledge).

Methods

Participants were 173 typically aging adults aged 60-90 years who were recruited to the Synapse Project and randomly allocated to a productive engagement activity (learning to quilt and/or conduct digital photography) or receptive engagement activity (socializing, or placebo cognitive tasks such as completing crosswords). Participants completed three flanker tasks at baseline and after completing the 14-week intervention program. IIV was calculated as the trial-to-trial variability in responding to congruent and incongruent trials in each task.

Results

Neither traditional intent-to-treat nor complier average causal effect modeling analyses showed any significant improvements in IIV for either intervention group. Further, Bayesian analyses showed that there was moderate evidence in favor of the null hypothesis.

Conclusion

An intensive cognitive activity intervention did not result in a reduction in IIV. We suggest that intervention programs may need to specifically engage cognitive domains associated with IIV (i.e., attention, executive control) for improvements to be observed. Additionally, other design factors such as using a longer duration and/or applying the intervention to atypically aging groups, such as those with mild cognitive impairment, may increase the likelihood of significantly reducing IIV via an intervention.

Absence of differences in the learning rate of a speed-accuracy movement task between women patients with mild and major depression and healthy adult women

This study tested the hypothesis that women patients with depression should perform movements more slowly and with greater variability, and their learning rate should be lower compared with age-matched healthy adult women. Three groups of adult women subjects (aged 33-37 years, women patients with mild and major depression and healthy adult women, n = 20 in each group) performed five series (20 repetitions in each series) of a speed-accuracy hand-movement task (SAT). The mean movement speed (V_a) of the SAT was lower and more stable (the coefficient of variation of V_a was lower) in women patients with major depression compared with those with minor depression and healthy adult women during the first series of the SAT. Only the V_a and movement accuracy (path of movement, S) of the SAT varied significantly in the five learning series regardless of the subject group (healthy women subjects and women patients with minor and major depression). The intraindividual variability of reaction time, V_a, maximal movement velocity to the target (tV_max), time to tV_max, and S did not change significantly in any of the groups. Our research data showed that although women patients with depression performed speed-accuracy movements more slowly, the stability of the performance of their movements and their learning rate did not differ from those of age-matched healthy adult women.

Intraindividual variability in children is related to informant ratings of attention and executive function

Objective: Attention and executive function (EF) deficits are ubiquitous in neurodevelopmental disorders including Attention Deficit/Hyperactivity Disorder (ADHD), as are high levels of intraindividual variability (IIV). Attention and EF are typically assessed using informant ratings and objective measures; however, discrepancies between different metrics often make it difficult to fully characterize a child's attention capabilities, and IIV has been proposed as a potentially useful discriminator. Our objective was to explore the relationship between IIV, using the residualized intraindividual standard deviation (rISD) method, and informant ratings of attention and EF in a mixed pediatric sample, to determine the potential utility of IIV for aiding attention diagnostics. Another commonly used, though controversial, IIV indicator, the coefficient of variation (ICV), was calculated for comparison purposes. Method: We assessed 51 children with varying degrees of attention and EF deficits. Measures included parent and teacher responses on the Comprehensive Executive Function Inventory (CEFI) and response times (RT) on a go/no-go task, which were used to estimate IIV. Results: Mean RT, rISD, and ICV were significantly related to parent and teacher ratings of attention, though ICV showed a relatively weaker association. rISD also showed associations with parent ratings of working memory and self-monitoring, as well as teacher ratings of working memory. Conclusion: The significant, and relatively stronger, relationship between rISD and parent and teacher ratings of attention supports the use of this metric, compared to mean RT and ICV. The rISD indicator of IIV thus shows potential utility as a unique and objective measure of attention in children across various neurodevelopmental disorders and, with additional research, may prove useful for diagnosis of attention problems.

Affective dynamics in bipolar spectrum psychopathology: Modeling inertia, reactivity, variability, and instability in daily life

BACKGROUND

Bipolar psychopathology is characterized by affective dysregulation independent of mood episodes. However, previous research has relied on laboratory-based emotion-eliciting tasks or retrospective questionnaires that do not take into account temporal dynamics of affect. Thus, the present study examined affective dynamics (reactivity, variability, instability, and inertia) of low and high arousal negative affect (NA) and positive affect (PA) in daily life in those at risk for bipolar psychopathology.

METHODS

Undergraduates (n = 135) completed the Hypomanic Personality Scale and experience sampling surveys assessing affective experiences 8 times daily for 7 days.

RESULTS

HPS scores were associated with greater reactivity of NA when experiencing negative or stressful events, variability of NA (high and low arousal) and PA (high arousal), and instability of NA and PA (high and low arousal) in daily life. HPS scores were associated with a high probability of acute increases in NA and PA and were unassociated with levels of inertia.

LIMITATIONS

This study only examined short-term dynamics over 7 days. Future studies should model both short- and long-term dynamics and whether these dynamics predict behavioral outcomes.

CONCLUSIONS

These results provide evidence that bipolar spectrum psychopathology is characterized by reactivity of NA as well as variability, instability, and acute increases in NA and PA in daily life over-and-above mean levels of affect. Modeling affective dynamics may provide context-relevant information about the course and trajectory of bipolar spectrum psychopathology and should facilitate the use of experience sampling methodology to study and intervene in mood lability in patients with bipolar disorders.

A Comprehensive Comparison of Quantifications of Intraindividual Variability in Response Times: A Measurement Burst Approach

OBJECTIVES

To formally identify and contrast the most commonly-employed quantifications of response time inconsistency (RTI) and elucidate their utility for understanding within-person (WP) and between-person (BP) variation in cognitive function with increasing age.

METHOD

Using two measurement burst studies of cognitive aging, we systematically identified and computed five RTI quantifications from select disciplines to examine: (a) correlations among RTI quantifications; (b) the distribution of BP and WP variation in RTI; and (c) the comparability of RTI quantifications for predicting attention switching.

RESULTS

Comparable patterns were observed across studies. There was significant variation in RTI BP as well as WP across sessions and bursts. Correlations among RTI quantifications were generally strong and positive both WP and BP, except for the coefficient of variation. Independent prediction models indicated that slower mean response time (RT) and greater RTI were associated with slower attention switching both WP and BP. For selecting simultaneous prediction models, collinearity resulted in inflated standard errors and unstable model estimates.

DISCUSSION

RTI reflects a novel dimension of performance that is a robust and theoretically informative predictor of BP and WP variation in cognitive function. Among the plenitude of RTI quantifications, not all are interchangeable, nor of comparable predictive utility.

Measuring longitudinal cognition: Individual tests versus composites

Introduction

Longitudinal cohort studies of cognitive aging must confront several sources of within-person variability in scores. In this article, we compare several neuropsychological measures in terms of longitudinal error variance and relationships with biomarker-assessed brain amyloidosis (Aβ).

Methods

Analyses used data from the Wisconsin Registry for Alzheimer's Prevention. We quantified within-person longitudinal variability and age-related trajectories for several global and domain-specific composites and their constituent scores. For a subset with cerebrospinal fluid or amyloid positron emission tomography measures, we examined how Aβ modified cognitive trajectories.

Results

Global and theoretically derived composites exhibited lower intraindividual variability and stronger age × Aβ interactions than did empirically derived composites or raw scores from single tests. For example, the theoretical executive function outperformed other executive function scores on both metrics.

Discussion

These results reinforce the need for careful selection of cognitive outcomes in study design, and support the emerging consensus favoring composites over single-test measures.

•

Identifying early cognitive change requires tests with low error variance.

•

In a middle-aged sample, composites were less noisy than single tests.

•

Global and theory-driven composites outperformed data-driven composites.

Inter-trial variability in brain activity as an indicator of synergistic effects of HIV-1 and drug abuse

BACKGROUND

The objective of this investigation was to detect evidence of the synergism in the effects of HIV-1 and drug abuse on brain function that has been hypothesized but rarely shown. The investigation incorporated several noteworthy improvements in the approach. It used urine toxicology tests to exclude participants complicated by recent methadone use and illicit drug use. Also, it defined drug abuse on a scale that considered symptom severity. Most importantly, it examined inter-trial variability in brain activity as a potentially more sensitive indicator of group differences and functional impairment than the across-trial average.

METHODS

173 participants were assigned to groups defined by their HIV-1 serostatus and Drug Abuse Screening Test score (DAST < vs. > = 6). They completed a simple letter discrimination task including rare target and rare nontarget stimuli. Event-related electroencephalographic responses and key press responses were measured on each trial. During a separate assessment, posturographic measures were recorded.

RESULTS

The inter-trial standard deviation of P300-like activity was superior to the mean amplitude of this activity in differentiating the groups. Unlike the mean, it revealed synergistic statistical effects of HIV and drug abuse. It also correlated significantly with static ataxia.

CONCLUSIONS

Inter-trial variability in P300-like activity is a useful marker for detecting subtle and episodic disruptions in brain function. It demonstrates greater sensitivity than the mean amplitude for detecting differences across groups. Also, as a putative indicator of a disruption in the attentional monitoring of behavior, it predicts subtle impairments in gross motor function.

Intraindividual sleep variability and its association with insomnia identity and poor sleep

OBJECTIVE

Insomnia identity refers to the conviction that one has insomnia, which can occur independently of poor sleep. Night-to-night variability in sleep (termed intraindividual variability [IIV]) may contribute to insomnia identity yet remain undetected via conventional mean analyses. This study compared sleep IIV across four subgroups: noncomplaining good sleepers (NG), complaining poor sleepers (CP), complaining good sleepers (CG), and noncomplaining poor sleepers (NP).

METHODS

This study analyzed 14 days of sleep diary data from 723 adults. Participants were classified according to presence/absence of a sleep complaint and presence/absence of poor sleep. A 2 × 2 multivariate analysis of covariance (MANCOVA) was performed to explore differences on five measures of sleep IIV: intraindividual standard deviation in total sleep time (iSD TST), sleep onset latency (iSD SOL), wake after sleep onset (iSD WASO), number of nightly awakenings (iSD NWAK), and sleep efficiency (iSD SE).

RESULTS

MANCOVA revealed significant main effects of poor sleep, sleep complaint, and their interaction on sleep IIV. Poor sleepers exhibited greater IIV across all sleep parameters compared to good sleepers. Similarly, individuals with a sleep complaint exhibited greater IIV compared to individuals with no complaint. The interaction revealed that iSD SOL was significantly greater among CP than NP, and iSD NWAK was significantly greater among CG than NG.

CONCLUSIONS

Greater night-to-night variability in specific sleep parameters was present among complaining versus noncomplaining sleepers in good and poor sleep subgroups. These findings suggest certain aspects of sleep consistency may be salient for treatment-seeking individuals based on their quantitative sleep status.

Effectiveness of Intraindividual Variability in Detecting Subtle Cognitive Performance Deficits in Breast Cancer Patients

OBJECTIVES

The purpose of this study was to determine if intraindividual variability would be more sensitive than speed or accuracy in detecting subtle cancer-related cognitive disturbance.

METHODS

Data were from a previous study in which 60 breast cancer (BC) patients underwent neuropsychological assessment before commencement of chemotherapy and again following each chemotherapy cycle. Sixty healthy controls were tested at equivalent intervals. Hierarchical linear modeling was used to compare the BC and control groups in terms of accuracy, mean reaction time, and intraindividual variability in reaction time on a computerized continuous performance test with three conditions: a simple reaction time task, a "1-back" task, and a "2-back" task.

RESULTS

An increase in accuracy and response speed over sessions was noted on some tasks in the sample as a whole but there were no differences in these parameters between the BC patients and the controls on any condition. There was a significant group difference in change in intraindividual variability across sessions (i.e., a "group × session interaction"), albeit only on the most complex "2-back" task. Intraindividual variability declined in the control group (i.e., consistency improved with practice) but this practice effect was significantly attenuated in the BC patients. There was no main effect of group on the "2-back" task.

CONCLUSIONS

Results support our hypothesis that intraindividual variability is a more sensitive indicator of subtle cognitive disturbance than conventional speed or accuracy measures and may have potential in the assessment of mild cognitive impairment in patients with non-central nervous system cancers. (JINS, 2018, 24, 724-734).

Reliabilities of Intraindividual Variability Indicators with Autocorrelated Longitudinal Data: Implications for Longitudinal Study Designs

Intraindividual variability can be measured by the intraindividual standard deviation ([Formula: see text]), intraindividual variance ([Formula: see text]), estimated hth-order autocorrelation coefficient ([Formula: see text]), and mean square successive difference ([Formula: see text]). Unresolved issues exist in the research on reliabilities of intraindividual variability indicators: (1) previous research only studied conditions with 0 autocorrelations in the longitudinal responses; (2) the reliabilities of [Formula: see text] and [Formula: see text] have not been studied. The current study investigates reliabilities of [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and the intraindividual mean, with autocorrelated longitudinal data. Reliability estimates of the indicators were obtained through Monte Carlo simulations. The impact of influential factors on reliabilities of the intraindividual variability indicators is summarized, and the reliabilities are compared across the indicators. Generally, all the studied indicators of intraindividual variability were more reliable with a more reliable measurement scale and more assessments. The reliabilities of [Formula: see text] were generally lower than those of [Formula: see text] and [Formula: see text], the reliabilities of [Formula: see text] were usually between those of [Formula: see text] and [Formula: see text] unless the scale reliability was large and/or the interindividual standard deviation in autocorrelation coefficients was large, and the reliabilities of the intraindividual mean were generally the highest. An R function is provided for planning longitudinal studies to ensure sufficient reliabilities of the intraindividual indicators are achieved.

Response Time Consistency Is an Indicator of Executive Control Rather than Global Cognitive Ability

OBJECTIVES

Intraindividual variability increases with age, but the relative strength of association with cognitive domains is still unclear. The objective of this study was to examine the relation between cognitive domains and the shape and spread of response time (RT) distributions as indexed by intraindividual standard deviation (ISD), and ex-Gaussian parameters (μ, σ, τ).

METHODS

Healthy adults (40 young [aged 18-30 years], 40 young-old [aged 65-74 years], and 41 old-old [aged 75-85 years]) completed neuropsychological testing and a touch-screen attention task from which ISD and ex-Gaussian parameters were derived. The relation between RT performance and cognitive domains (memory, processing speed, executive functioning) was examined with structural equation modeling (SEM), and the predictive power of RT distribution indices over age was investigated with linear regression.

RESULTS

ISD, μ, and τ, but not σ, showed a linear increase with age group. An SEM showed that independent of age, τ was most strongly associated with executive functioning, while μ exhibited less critical associations. Linear regression indicated that μ and τ explained a significant portion of variance in processing speed and executive ability in addition to age group. Memory was more parsimoniously predicted by age, without any significant contribution of ex-Gaussian parameters.

CONCLUSIONS

The findings suggest that exceptionally slow responses convey attention lapses through wavering of cognitive control, which strongly correspond to executive functioning tests. General slowing and extremely slow responses predicted processing speed and executive performance beyond age group, indicating that RT metrics are sensitive to differences in cognitive ability. (JINS, 2018, 24, 456-465).

Intraindividual variability in attentional vigilance in children with epilepsy

Attentional vigilance, the ability to maintain focus over time, is frequently impaired in childhood epilepsy. Typically, indices of Omissions (failure to detect a target) and Commissions (responding to a nontarget) are considered primary indices of attentional vigilance. Recently, the concept of intraindividual variability (IIV) has been identified as an important measure of attentional vigilance in several pediatric and adult clinical populations, but has not yet been systematically examined in childhood epilepsy. Here, we examined IIV on the Connors Continuous Performance Task-II (CCPT-II) for 144 newly diagnosed children with epilepsy (age 8-18years) and a matched age group of healthy children (n=82). Intraindividual variability showed a large effect size difference (d=0.68) between groups. In addition, IIV significantly predicted both intellectual functioning and academic achievement. These findings support the utility of examining IIV in the assessment of attentional ability in childhood epilepsy.

Modeling Intraindividual Dynamics Using Stochastic Differential Equations: Age Differences in Affect Regulation

Objectives

Life-span theories of aging suggest improvements and decrements in individuals' ability to regulate affect. Dynamic process models, with intensive longitudinal data, provide new opportunities to articulate specific theories about individual differences in intraindividual dynamics. This paper illustrates a method for operationalizing affect dynamics using a multilevel stochastic differential equation (SDE) model, and examines how those dynamics differ with age and trait-level tendencies to deploy emotion regulation strategies (reappraisal and suppression).

Method

Univariate multilevel SDE models, estimated in a Bayesian framework, were fit to 21 days of ecological momentary assessments of affect valence and arousal (average 6.93/day, SD = 1.89) obtained from 150 adults (age 18-89 years)-specifically capturing temporal dynamics of individuals' core affect in terms of attractor point, reactivity to biopsychosocial (BPS) inputs, and attractor strength.

Results

Older age was associated with higher arousal attractor point and less BPS-related reactivity. Greater use of reappraisal was associated with lower valence attractor point. Intraindividual variability in regulation strategy use was associated with greater BPS-related reactivity and attractor strength, but in different ways for valence and arousal.

Discussion

The results highlight the utility of SDE models for studying affect dynamics and informing theoretical predictions about how intraindividual dynamics change over the life course.

Fusing Biodiversity Metrics into Investigations of Daily Life: Illustrations and Recommendations With Emodiversity

Objectives

Functionalist emotion and ecological systems theories suggest emodiversity-the variety and relative abundance of individuals' emotion experiences-is beneficial for psychological and physical health and may change with age. This paper examines and provides recommendations for operationalization of diversity-type intraindividual variability (IIV) constructs using intensive longitudinal data, and demonstrates the utility of emodiversity by examining its links to physical health moderated by mean levels of emotion and age.

Method

Using data from a daily diary study of 138 adults (age 40 to 65 years), we consider how item selection, response scale, choice of diversity index, and number of occasions enable/constrain mapping to theory, measurement reliability, and empirical inquiry.

Results

Item selection and response scale had limited influence on rank-order differences in diversity. Reliable measurement (r ≥ .8) required a minimum of 6 to 12 occasions depending on choice of index, theoretical conception, study design, and distribution of diversity scores. The empirical findings suggest mean level of negative affect, rather than age, moderates the relation between negative emodiversity and health.

Discussion

This study provides recommendations for the calculation of diversity-type IIV constructs and illustrates the potential for study of emodiversity to contribute to understanding of successful aging.

The impact of physical activity and sex differences on intraindividual variability in inhibitory performance in older adults

It is well-known that processing speed and executive functions decline with advancing age. However, physical activity (PA) has a positive impact on cognitive performances in aging, specifically for inhibition. Less is known concerning intraindividual variability (iiV) in reaction times. This study aims to investigate the influence of PA and sex differences on iiV in inhibitory performance during aging. Healthy adults were divided into active and sedentary groups according to PA level. To analyse iiV in reaction times, individual mean, standard deviation and the ex-Gaussian parameters were considered. An interaction between activity level and sex was revealed, sedentary females being slower and more variable than sedentary men. No sex differences were found in the active groups. These results indicate that the negative impact of sedentariness on cognitive performance in older age is stronger for females. The present findings underline the need to consider sex differences in active aging approaches.

Intraindividual Stepping Reaction Time Variability Predicts Falls in Older Adults With Mild Cognitive Impairment

Background

Reaction time measures have considerable potential to aid neuropsychological assessment in a variety of health care settings. One such measure, the intraindividual reaction time variability (IIV), is of particular interest as it is thought to reflect neurobiological disturbance. IIV is associated with a variety of age-related neurological disorders, as well as gait impairment and future falls in older adults. However, although persons diagnosed with Mild Cognitive Impairment (MCI) are at high risk of falling, the association between IIV and prospective falls is unknown.

Methods

We conducted a longitudinal cohort study in cognitively intact (n = 271) and MCI (n = 154) community-dwelling adults aged 70-90 years. IIV was assessed through a variety of measures including simple and choice hand reaction time and choice stepping reaction time tasks (CSRT), the latter administered as a single task and also with a secondary working memory task.

Results

Logistic regression did not show an association between IIV on the hand-held tasks and falls. Greater IIV in both CSRT tasks, however, did significantly increase the risk of future falls. This effect was specific to the MCI group, with a stronger effect in persons exhibiting gait, posture, or physiological impairment.

Conclusions

The findings suggest that increased stepping IIV may indicate compromised neural circuitry involved in executive function, gait, and posture in persons with MCI increasing their risk of falling. IIV measures have potential to assess neurobiological disturbance underlying physical and cognitive dysfunction in old age, and aid fall risk assessment and routine care in community and health care settings.

A Systematic Review of Longitudinal Associations Between Reaction Time Intraindividual Variability and Age-Related Cognitive Decline or Impairment, Dementia, and Mortality

OBJECTIVES

Intraindividual variability (IIV) in reaction time refers to the trial-to-trial fluctuations in responding across a given cognitive task. Cross-sectional research suggests that IIV increases with normal and neuropathological ageing and it may serve as a marker of neurobiological integrity. This raises the possibility that IIV may also predict future cognitive decline and, indeed, neuropathology. Therefore, we conducted a systematic review to address these issues.

METHODS

A search of electronic databases Embase, Medline, PsycINFO, and Web of Science was completed on May 17, 2016 that identified longitudinal investigations of IIV in middle-aged or older adults.

RESULTS

A total of 688 studies were initially identified of which 22 met the inclusion criteria. Nine included longitudinal IIV measures and 17 predicted subsequent outcome (cognitive decline or impairment, dementia, mortality) from baseline IIV. The results suggested IIV increased over time, particularly in participants aged over 75 years. Greater baseline IIV was consistently associated with increased risk of adverse outcomes including cognitive decline or impairment, and mortality.

CONCLUSIONS

Increased IIV over time is associated with normal ageing. However, further increases in IIV over and above those found in normal ageing may be a risk factor for future cognitive impairment or mortality. Measures of IIV may, therefore, have considerable potential as a supplement to existing clinical assessment to aid identification of individuals at risk of adverse outcomes such as dementia or death. (JINS, 2017, 23, 431-445).

Relationships Among Nightly Sleep Quality, Daily Stress, and Daily Affect

Objectives.

We explored the prospective, microlevel relationship between nightly sleep quality (SQ) and the subsequent day's stress on positive (PA) and negative affect (NA) as well as the moderating relationships between nightly SQ, subsequent stress, and subsequent PA on NA. We investigated whether age moderated these relationships.

Method.

We collected 56 days of sleep, stress, and affect data using daily diary questionnaires (N = 552). We used multilevel modeling to assess relationships at the between- and within-person levels.

Results.

Daily increases in SQ and decreases in stress interacted to predict higher daily PA and lower daily NA. Better SQ in older adults enhanced the benefits of PA on the stress-NA relationship more during times of low stress, whereas better sleep in younger adults enhanced the benefits of PA more during times of high stress. Between-person effects were stronger predictors of well-being outcomes than within-person variability.

Discussion.

The combination of good SQ and higher PA buffered the impact of stress on NA. The moderating impact of age suggests that sleep and stress play different roles across adulthood. Targeting intervention and prevention strategies to improve SQ and enhance PA could disrupt the detrimental relationship between daily stress and NA.

Intraindividual variability in cortisol: Approaches, illustrations, and recommendations

Most of the variance in diurnal cortisol is attributable to intraindividual variability (IIV), defined as relatively short-term, reversible changes. Multiple methods for measuring IIV have been proposed, and some have already been applied to cortisol IIV. In the present review, measurement methods are described and applied to simulated cortisol data with known underlying differences in IIV and to real cortisol data from first-year law students. More slope variance and more residual or net variance were well captured by their individual standard deviations. Explorations of reliability suggested that 10 slopes and 50 residuals result in reliable and stable estimates of the individual standard deviations. A data-analytic plan for cortisol IIV is provided.

Associations between reaction time measures and white matter hyperintensities in very old age

In old age, a relationship has been reported between intraindividual variability (IIV) in reaction time and white matter integrity as evidenced by white matter hyperintensities (WMH). However, it is unclear how far such associations are due to incipient neurodegenerative pathology in the samples investigated. The present study examined the relationship between IIV and WMH in older individuals (N=526) drawn from the Sydney Memory and Ageing Study. Using a complex reaction time (RT) task, greater IIV and mean-RT were related to a higher WMH burden in the frontal lobe. Critically, significant associations remained having taken future dementia into account suggesting that they were not explained by incipient dementia. Additionally, independent measures of executive function accounted for the association between RT metrics and WHM. The results are consistent with the view that frontally-supported cognitive processes are involved in IIV-WMH relations, and that RT measures are sensitive to compromise in white matter structures in non-demented older individuals.