Associations between daily affect and sleep vary by sleep assessment type: What can ambulatory EEG add to the picture?

Can stimulants make you smarter, despite stealing your sleep?

Nonmedical use of psychostimulants for cognitive enhancement is widespread and growing in neurotypical individuals, despite mixed scientific evidence of their effectiveness. Sleep benefits cognition, yet the interaction between stimulants, sleep, and cognition in neurotypical adults has received little attention. We propose that one effect of psychostimulants, namely decreased sleep, may play an important and unconsidered role in the effect of stimulants on cognition. We discuss the role of sleep in cognition, the alerting effects of stimulants in the context of sleep loss, and the conflicting findings of stimulants for complex cognitive processes. Finally, we hypothesize that sleep may be one unconsidered factor in the mythology of stimulants as cognitive enhancers and propose a methodological approach to systematically assess this relation.

Monitoring Daily Sleep, Mood, and Affect Using Digital Technologies and Wearables: A Systematic Review

Background: Sleep and affective states are closely intertwined. Nevertheless, previous methods to evaluate sleep-affect associations have been limited by poor ecological validity, with a few studies examining temporal or dynamic interactions in naturalistic settings. Objectives: First, to update and integrate evidence from studies investigating the reciprocal relationship between daily sleep and affective phenomena (mood, affect, and emotions) through ambulatory and prospective monitoring. Second, to evaluate differential patterns based on age, affective disorder diagnosis (bipolar, depression, and anxiety), and shift work patterns on day-to-day sleep-emotion dyads. Third, to summarise the use of wearables, actigraphy, and digital tools in assessing longitudinal sleep-affect associations. Method: A comprehensive PRISMA-compliant systematic review was conducted through the EMBASE, Ovid MEDLINE(R), PsycINFO, and Scopus databases. Results: Of the 3024 records screened, 121 studies were included. Bidirectionality of sleep-affect associations was found (in general) across affective disorders (bipolar, depression, and anxiety), shift workers, and healthy participants representing a range of age groups. However, findings were influenced by the sleep indices and affective dimensions operationalised, sampling resolution, time of day effects, and diagnostic status. Conclusions: Sleep disturbances, especially poorer sleep quality and truncated sleep duration, were consistently found to influence positive and negative affective experiences. Sleep was more often a stronger predictor of subsequent daytime affect than vice versa. The strength and magnitude of sleep-affect associations were more robust for subjective (self-reported) sleep parameters compared to objective (actigraphic) sleep parameters.

Nightly Sleep Predicts Next-Morning Expectations for Stress and Positive Experiences

OBJECTIVE

Abundant research has linked nightly sleep as an antecedent of daily psychosocial experiences; however, less is known about sleep's influence on daily expectations of these experiences. Therefore, this research examined the day-to-day associations of sleep quality, duration, and efficiency with next-day expectations for stress(ors) and positive experiences, as well as whether these expectations were related to end-of-day reports of physical symptoms.

METHODS

In Study 1, U.S. adults ( n = 354; ages 19 to 74) completed twice-daily diaries for 10 weekdays about sleep, expectations for encountering daily stressors and positive events, and physical symptoms. In Study 2, adults in Canada ( n = 246; ages 25 to 87) wore a sleep watch for 14 consecutive days and completed mobile surveys 5×/day about sleep, stressfulness and pleasantness expectations, and physical symptoms.

RESULTS

Multilevel models indicated that self-reported sleep quality and duration, but not efficiency, were associated with lower next-day expectations for stressors (Study 1) and stressfulness (Study 2). Self-reported sleep quality (Study 1) and all sleep indices (Study 2) predicted greater next-day expectations for positive events and pleasantness, respectively. For actigraphy-assessed sleep (Study 2), only longer-than-usual actigraphic sleep duration was associated with lower stressfulness expectations, whereas both sleep duration and efficiency were positively linked with daily pleasantness expectations. Only pleasantness expectations (Study 2)-but not daily stressfulness and event expectations (Study 1)-predicted end-of-day physical symptoms.

CONCLUSION

Findings suggest the importance of sleep on expectations of next-day stress and positive experiences, of which may have implications for daily physical health.

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

STUDY OBJECTIVES

Consumer 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.

METHODS

119 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.

RESULTS

Nocturnal 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.

CONCLUSIONS

Positive 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 ID

ClinicalTrials.gov NCT04880629.

Protocol of the Budapest sleep, experiences, and traits study: An accessible resource for understanding associations between daily experiences, individual differences, and objectively measured sleep

Sleep is both a neurophysiological state and a biologically necessary behavior that performs a variety of indispensable roles for human health, development, and cognitive functioning. Despite this, comparatively little is known about the relationships between daily experiences and sleep features. Importantly, these relationships are bidirectional in nature, may be differently associated with subjectively and objectively assessed sleep, and may also be modulated by individual differences To address this challenge, we created the Budapest Sleep, Experiences, and Traits Study (BSETS), a multidisciplinary observational sleep study utilizing novel remote EEG devices. BSETS was designed to establish a dataset for future use in investigating the relationships between sleep features and daily experiences. In this paper we describe the protocol of the currently ongoing BSETS, which examines a community-dwelling sample of over 250 healthy participants who are studied in a naturalistic setting using a large questionnaire assessing psychological, demographic, and anthropometric information, as well as evening/morning diaries of sleep and daily experiences, and mobile EEG recordings over a period of 7 days. This dataset will become an accessible resource to the wider scientific community and can be utilized to investigate the complex multidirectional relationships between objectively and subjectively measured sleep, daily experiences, and individual differences, bestowing it with significant value for sleep researchers as well as practitioners working in clinical settings with patients suffering from disordered sleep.

Sleep, Affect, and Emotion Reactivity in First-Year College Students: A Daily Diary Study

BACKGROUND

Sleep is an important factor in well-being, especially during the transition to college when academic and social commitments increase. Identifying factors that contribute to poor sleep (including short duration and increased variability in duration) can support development of interventions. Affect and emotion reactivity are factors that could contribute to sleep, and have not been studied in relation to sleep variables among first-year college students during their adjustment to the college environment. This adjustment might be difficult for some students, and therefore elicit affect fluctuations that contribute to poor sleep. Alternatively, sleep could contribute to daily affect. The present daily diary study examined bidirectional relations between daily sleep and affect, as well as between emotion reactivity and sleep (duration and variability) and affect (daily and overall variability) in first-year college students.

METHOD

First-year college students (n = 244; 86.1% female) completed a baseline survey including measures of emotion reactivity and anxiety and depressive symptoms, followed by 7 days of a once-per-day diary, reporting on their affect and sleep duration.

RESULTS

On days when individuals reported increased sleep duration, they also tended to experience greater positive affect the following day (p = .01). Those who experienced high levels of emotion reactivity also experienced more negative affect (p < .001) and negative affect variability (p < .001).

CONCLUSION

Emotion reactivity might identify college students who experience more negative affect and are possibly at risk to develop mental health disorders. The importance of sleep health should continue to be emphasized to students as they transition to college.

Are Short Duration Naps Better than Long Duration Naps for Mitigating Sleep Inertia? Brief Report of a Randomized Crossover Trial of Simulated Night Shift Work

OBJECTIVE

We sought to test the effects of different duration naps on post-nap cognitive performance during simulated night shifts.

METHODS

We used a randomized laboratory-based crossover trial design with simulated 12-hr night shifts and each participant completing three conditions of 72 hrs each (Clinicaltrials.gov; registration # NCT04469803). The three conditions tested included no-nap, a 30-min nap opportunity, and a 2-hr nap opportunity. Naps occurred at 02:00 hrs. Cognitive performance was assessed with the Brief 3-min Psychomotor Vigilance Test (PVT-B). Four PVT-B measures include: reaction time (RT in milliseconds (ms)), lapses (RT > 355 ms), false starts (reactions before stimulus or RT <100 ms), and speed (1,000/RT). The PVT-B was performed at the start of the simulated night shift (19:00), end of shift (07:00), pre-nap (02:00), and at 0 mins, 10 mins, 20 mins, and 30 mins following the 30-min and 2-hr nap conditions. Simultaneously, participants reported subjective ratings of fatigue and other constructs.

RESULTS

Twenty-eight (15 female), mostly certified emergency medical technicians or paramedics, consented to participate. For all three conditions, looking within condition, PVT-B lapse performance at the end of the 12-hr simulated night shift (at 07:00) was poorer compared to shift start (p < 0.05). Performance on PVT-B speed, RT, and false starts were poorer at shift end than shift start for the no-nap and 30-min nap conditions (p < 0.05), but not for the 2-hr nap condition (p > 0.05). Compared to pre-nap measures, performance on the PVT-B assessed at 0 mins post-nap showed significant performance declines for lapses and speed for both the 30-min and 2-hr nap conditions (p < 0.05), but not at 10, 20, or 30 mins post-nap. After waking from the 2-hr on-shift nap opportunity (at 0 mins), participants rated sleepiness, difficulty with concentration, and alertness poorer than pre-nap (p < 0.05). Participants in the 30-min nap condition rated alertness poorer immediately after the nap (at 0 mins) compared to pre-nap (p < 0.05).

CONCLUSIONS

While sleep inertia was detectable immediately following short 30-min and long 2-hr nap opportunities during simulated night shift work, deficits in cognitive performance and subjective ratings quickly dissipated and were not detectable at 10-30 mins post-nap.

The role of positive affect processes in the association between posttraumatic stress disorder symptoms and sleep: A multi-study design

OBJECTIVES

Posttraumatic stress disorder (PTSD) symptoms have been linked to sleep disturbances. Limited work has explored how positive affect processes may account for this relationship. Advancing research in this area, we utilized a multi-study design to investigate the role of positive affect processes (levels of positive affect, positive emotionality, hedonic deficits, negative affect interference) in the PTSD-sleep association.

METHODS

Data from 149 trauma-exposed firefighters (M_age = 38.93 ± 9.65, 5.40 % women) were collected between September 2021 and November 2021, and data from 119 trauma-exposed community members (M_age = 29.60 ± 8.67, 68.10 % women) were collected between February 2021 and December 2021. Participants completed an online survey on PTSD symptoms, sleep disturbances, and positive affect processes.

RESULTS

Positive affect levels (b = 0.03, 95 % confidence interval [CI] [0.01, 0.06]; firefighter sample), positive emotionality (b = 0.07, CI [0.03, 0.13]; community sample), and negative affect interference (b = 0.06, CI [0.01, 0.14]; community sample) significantly accounted for the associations between PTSD symptom severity and sleep disturbances controlling for the effects of gender and age.

CONCLUSION

Findings highlight the role of positive affect processes in the link between PTSD and sleep, and support addressing positive affect processes as potential targets in clinical interventions for co-occurring PTSD-sleep problems.

Pre-sleep affect predicts subsequent REM frontal theta in nonlinear fashion

Pre-sleep affect is thought to influence sleep, but associations with both sleep architecture and the electroencephalographic (EEG) power spectrum are mixed. In this pre-registered study, we assessed negative valence and arousal 1 h pre-sleep in 52 adults drawn from the community, then recorded one night of polysomnography (PSG) in participants' own homes. Pre-sleep affect was not associated with nonrapid eye movement (NREM) or rapid eye movement (REM) sleep architecture parameters, but we did observe inverted U-shaped relationships between both negative valence and arousal and REM frontal theta power, such that theta power was highest at moderate negative valence and arousal, and lowest at either affective extreme. When entered into a model together, both valence and arousal accounted for independent variance. Secondary analyses revealed a similar quadratic association with pre-sleep positive valence, suggesting a nonspecific effect of pre-sleep valence on REM frontal theta. Robustness checks confirmed that effects were not explained by homeostatic sleep pressure or sleep timing. Our results suggest that mixed findings in the literature may reflect different ends of a quadratic function, underscoring the importance of assessing how different components of pre-sleep affect relate to sleep.

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 Information

The online version contains supplementary material available at 10.1007/s42761-021-00082-6.