0344 Age-Related Longitudinal Trajectories in NREM and REM Spectral Power

Introduction

Knowledge of how aging impacts sleep physiology is based almost exclusively on cross-sectional studies. Longitudinal studies, by contrast, can inform how macro- and micro-features of NREM and REM sleep change dynamically across time in individual trajectories. For the current work, we conducted quantitative EEG analyses from a longitudinal polysomnography study to inform age-related trajectories in sleep macro- and micro-architecture.

Methods

We conducted a secondary data analysis on 2208 participants in the Sleep Heart Health Study (mean age =62.47, SD=10.46, 55.30% females). Participants underwent one night of in-home polysomnography recording during two study visits (M=5.21 years apart, SD=0.53). Spectral power density was calculated for each 0.5 Hz frequency bin for NREM and REM sleep separately.

Results

In cross-sectional analyses, older chronological age was significantly associated with worse sleep macro-architecture. Plots of the individual trajectories over 5 years, however, revealed considerable inter-individual variability in whether sleep physiology was preserved or declined. Interestingly, there were strong associations between the longitudinal changes in power density in NREM and REM sleep (slow oscillations: r=.53 [.50-.56]; delta: r=.58 [.55-.60]; alpha: r=.69 [.67-.71]; sigma: r=.74 [.73-.76]; beta: r=.82 [.80-.83]; ps<.001). The strongest NREM-REM association was for theta band power (r=.85 [.83-.86]), particularly in the 5.5-6.0 Hz bin (r=.94, [.94, .95]).

Conclusion

There is substantial inter-individual variability in how aging impacts sleep physiology. Nevertheless, within individuals, power density declines similarly across NREM and REM stages, with nearly perfect convergence for theta activity, indicating a common age-related neurobiological mechanism.

Support

The National Sleep Research Resource is supported by NIH HL114473.

0212 Questionnaire Assessment of Intraindividual Variability in Sleep: Inconsistent Sleep Can Be Worse Than Short Average Sleep

Introduction

The consequences of short sleep are well-documented, but recent evidence indicates that night-to-night consistency in sleep may be just as important. For the current work, we developed an intraindividual variability in sleep (IIV) questionnaire to make IIV measurement possible in single-time-point studies. We investigated whether self-reported IIV explained unique variance in sleep quality and health beyond average total sleep time (TST), focusing on a critical transition period (first semester of college) in which high variability was predicted.

Methods

First-semester college students (N=126, Mage=18.28, 75.40% females) completed an IIV questionnaire in which participants indicated their average sleep duration, then estimated how much their sleep duration deviated from their average duration for each day of a typical week. We quantified IIV as the mean day-to-day change in sleep. Participants also completed standard questionnaires on global sleep quality, social jetlag, daytime sleepiness, depression, and stress.

Results

Participants reported substantial IIV in their sleep durations (M=1.77 hours, SD=0.86) that was largely distinguishable from measures of social jetlag (r=.25) and average TST (r=-.18). Patterns of IIV differed across race/ethnicities: in white/Asian students, IIV was strongly associated with social jetlag (r=-.44) whereas in underrepresented minority students, IIV and social jetlag were separate constructs (r=-.03), suggesting that fluctuations in the latter group occur across all days of the week. Greater IIV was associated with significantly worse global sleep quality (r=.24, p=.01), stress (r=.20, p=.03), and depression, r=.20, p=.03). These associations were significant after adjusting for average TST, and only marginally reduced when controlling for social jetlag.

Conclusion

IIV in sleep/wake patterns can be captured using a questionnaire, and such measurement provides unique explanatory power to understanding sleep quality and mental health. Future research is needed to compare IIV questionnaire data to actigraphy data and to understand the underlying mechanisms by which inconsistent sleep detrimentally affects individuals.

Support

National Science Foundation (NSF 1920730)

0369 Sleep Disparities are Established by the First Month of College

Introduction

Short and poor quality sleep are particularly common in college students, likely impacting their ability to persist and succeed in difficult courses. In the current study, we investigated demographic-based sleep differences (sleep disparities) and demographic-based academic differences (achievement gaps) in first-semester college students, with the goal of informing whether sleep disparities contribute to achievement gaps.

Methods

From 2017 to 2018, first-semester undergraduate students at Baylor University completed the New2BU Survey [N=6,048, 61.9% female, 18.7% first-generation, 23.8% underrepresented racial/ethnic minority (URM)]. Data collection occurred within three to five weeks of classes beginning. The survey included self-reported weekday total sleep time (TST), which we classified as short sleep (≤6.9 hours), normal sleep (7-9 hours), or long sleep (>9 hours). Semester GPA data were obtained from university records for students’ first 4 semesters.

Results

There was evidence for both achievement gaps and sleep disparities. The risk for short sleep was increased in female students (p<.001; OR=1.20, 95%CI: 1.08-1.33), first-generation students (p=.02; OR=1.17, 95%CI: 1.03-1.33), and URM students (p<.001; OR=1.32, 95%CI: 1.16-1.50). The risk for long sleep increased substantially in first-generation students (p=.003, OR=1.92, 95%CI: 1.25-2.97) and URM students (p<.001; OR=2.41, 95%CI: 1.57-3.70), but not in female students (OR=0.88, 95%CI: 0.59-1.30). First-generation and URM students showed a 0.2-0.3 GPA reduction each semester relative to comparison groups (ps<.001), but short sleep and long sleep predicted GPA data up to four semesters later. Sleep-GPA correlations were modest in size (rs=.10-.14), but remained significant even after controlling for numerous demographic variables, high school GPA, and college entrance test scores.

Conclusion

Sleep disparities are noteworthy within the first month of college, and predictive of academic performance across four semesters. Addressing sleep health in all students—but particularly female, first-generation, and URM students—may increase academic success, bridge achievement gaps, and reduce health disparities.

Support

National Science Foundation (DRL 1920730)

0197 Chronotype is Influenced by Behavioral Choices and Can Fluctuate Across the Semester in STEM Students

Introduction

A delay in endogenous biological rhythms is assumed to cause undergraduate students to be “night owls,” but neurodevelopmental effects may only partially explain chronotype (circadian preference). Instead, perceived chronotype in students may result from poor sleep hygiene practices including bedtime social media use, afternoon caffeine consumption, and daytime napping. If so, then chronotype should be malleable in students to the extent that behavioral choices change.

Methods

We surveyed 1,120 undergraduate students who were enrolled in STEM courses across up to 3 time points during the semester. The survey assessed perceived chronotype (morning/evening type), global sleep quality, and daily habits that impact alertness and sleep hygiene (e.g., social media usage and timing, caffeine consumption and timing, and napping behavior).

Results

Relative to Morning Types, students who perceived themselves as being Evening Types showed 23.1% greater bedtime social media usage (t=3.14, p=.002), 35.1% greater daytime napping duration (t=4.44, p<.001), and a 44 minute later average time of caffeine consumption (even though total caffeine consumption was reduced; t=2.30, p=.022). Evening Types also reported lower subjective health (t=3.55, p<.001), with 14.2% of the association between chronotype and subjective health being mediated by bedtime social media use (direct effect: b=0.050, p=.002; indirect effect: b=0.009, p<.05). Ninety-one students reported switching from being Evening Types at baseline to Morning Types at a later survey; those who switched to Morning Types used less social media and consumed less caffeine after 5pm and they showed significant improvements across the semester in sleep duration, sleep quality, and exam scores (ps<.05).

Conclusion

Perceived chronotype is related to social media and caffeine consumption behaviors and is modifiable. Students who perceive themselves as night owls may find better health and academic success if they behave like morning larks.

Support

National Science Foundation (DRL 1920730)

0391 Gateways, Disparities, and Finals Week, Oh My! Translating Sleep Science from the Laboratory to the Classroom

Introduction

Organic chemistry can be an insurmountable “gateway” course for otherwise-qualified students in pre-health pathways. Recent data indicate that organic chemistry increases drop-out risk for females and underrepresented minority students (URMs), raising the provocative possibility that sleep disparities are an underrecognized contributor to achievement gaps in gateway STEM courses.

Methods

In Study 1, 481 students enrolled in organic chemistry courses completed sleep questionnaires at the beginning, midpoint, and end of the semester. In Study 2, non-chemistry majors were randomly assigned to normal sleep (8 hours) or sleep restriction (5.5 hours) before taking an organic chemistry virtual lecture and test. In Study 3, 35 students wore actigraphy for five nights and could earn extra credit on a mid-semester test by averaging ≥8 hours of sleep; actigraphy sleep durations were compared to 40 active-control students who only received sleep education.

Results

In Study 1 (classroom), URM and female students earned lower organic chemistry grades than comparison students, p<.001. Baseline weekday sleep duration predicted test grades across the semester, and students who improved their weekday sleep subsequently improved their organic chemistry grades. In Study 2 (laboratory), mild sleep loss impaired meta-cognitive judgments of organic chemistry learning, a potential causal mechanism for reduced persistence in chemistry courses. In Study 3 (classroom), when better sleep behaviors were incentivized by extra credit, students slept an hour longer/night than control groups (7.8 vs 6.8 hours, p<.001). These benefits persisted 1 month later into finals week when sleep behaviors were not externally incentivized (7.3 vs 6.3 hours, p=.001). Improving sleep improved performance on difficult short answer questions after correcting for pre-final grades (Madjusted=78% vs 72%, p=.04).

Conclusion

Sleep disparities contribute to achievement gaps in gateway STEM courses, but incentives can reverse poor sleep habits. University administrators should develop and implement behavioral change programs to reduce sleep disparities.

Support

National Science Foundation (DRL 1920730)

0101 Episodic Future Thinking Triggers Age-Related Differences in Spindles and Slow Oscillations

Introduction

In young adults, sleep spindles are theorized to represent memory consolidation. Spindle density may be especially prominent when young adults encode information that has future relevance. Older adults, on the other hand, show reduced capacity for future thinking and deficits in sleep-dependent memory consolidation. To advance these literatures, we investigated whether the process of mentally simulating the future (versus remembering the past) was associated with subsequent alterations to sleep microarchitecture in young and older adults.

Methods

64 healthy adults aged 18–84 completed a polysomnography adaptation night followed by two in-laboratory experimental nights. On both nights, participants completed the Modified Future Crovitz Test (MFCT) in which they mentally simulated only future events or remembered only past events (night order counterbalanced). To quantify the extent of future/past thinking, we conducted linguistics analyses on tense (future/past) using LIWC 2015 software.

Results

On the future-thinking night, young adults with greater future-tense MFCT scores showed significantly greater spindle density across frontal, midline, and central sites (r=.42 to r=.51), even when controlling for age, gender, and total word count (all ps < .01). The opposite was true for middle-to-older aged adults; greater future-tense MFCT scores were associated with less spindle density across midline and central sites after controlling for age, gender, and word count (r=-.44 to r=-.46, ps<.05). However, while spindle density decreased, frontal slow oscillations increased in older adults with greater future-tense MFCT scores (r=.39, p<.05). On the past-thinking night, spindle density and slow oscillations were unrelated to past-tense or future-tense MFCT scores for either age group.

Conclusion

Age-related deficits in memory consolidation may be due to impaired tagging of information as having future relevance, or impaired physiological responses during sleep to wake-based tagging. Addressing encoding—spindle interactions may inform why cognitive functioning declines in some adults more than others.

Support

Sleep Research Society Foundation

0193 Sleep Health Across Religions: A Consideration of Bidirectional Processes

Introduction

The psychology of religion literature indicates that religious engagement is beneficial to physical and mental health. Such effects might be mediated by sleep health, which causally affects mood, cognitive, and immune functioning. However, few studies have investigated whether religiosity is associated with better sleep, and no studies have considered the reverse causal direction: better sleep may impact religious behaviors or perceptions.

Methods

We conducted a secondary data analysis of 1,501 participants in Wave 5 of the Baylor Religion Survey (BRS-5). Completed in Spring 2017, the BRS-5 used Address Based Sample methodology to derive a population-based sample. The survey included questions on religious affiliation, behaviors, and perceptions (e.g., certainty of Heaven). Additionally, participants rated their difficulty falling asleep and their average total sleep time. We investigated whether participants were meeting AASM/SRS consensus guidelines of 7–9 hours/night.

Results

Religious affiliation was associated with sleep duration, but not in the predicted direction. Atheists/Agnostics (73%) were significantly more likely to report meeting consensus sleep duration guidelines than religiously-affiliated individuals (65%), p<.05. For example, Atheists/Agnostics reported better sleep duration than Catholics (63%, p<.01) and Baptists (55%, p<.001). Atheists/Agnostics also reported less difficulty falling asleep at night than Catholics (p=.02) and Baptists (p<.001). The effects persisted when controlling for age and were particularly evident in members of African American congregations. Perceptions of getting into Heaven were significantly higher in participants who obtained better sleep duration, p<.05, but interestingly, such beliefs/perceptions were unrelated to difficulty falling asleep at night, suggesting that better sleep may lead to these perceptions rather than vice versa.

Conclusion

In contrast to predictions, religious affiliation was associated with significantly poorer sleep health. Poor sleep health has implications for physical and mental health, and seemingly also religious perceptions/beliefs. Future experimental work is required to disentangle the causal direction of sleep-religiosity associations.

Support

The Baylor Religion Survey was supported by the John Templeton Foundation.

Freezing of gait subtypes have different cognitive correlates in Parkinson's disease

BACKGROUND

Freezing of gait (FOG) is a major concern for Parkinson's disease (PD) patients because it is a leading cause of falls and is associated with poor quality of life. The pathophysiology is unknown but it is hypothesized that it relates to cognitive abnormalities; particularly executive and visuospatial dysfunction. However, prior results have been discrepant. Pharmacologic subtypes of FOG include those that are responsive and unresponsive to levodopa.

OBJECTIVE

To determine whether executive and visuospatial dysfunction are associated specifically with the levodopa unresponsive subtype of FOG.

METHODS

135 PD subjects completed a single assessment included FOG questionnaire, UPDRS motor scale, comprehensive cognitive battery and measure of hallucinations. Analyses compared unresponsive (n = 16), responsive (n = 20) and no FOG (n = 99) subtypes.

RESULTS

The unresponsive subtype had a significantly older age of onset of PD than the responsive group (p = .03) and had worse motor scores (p = .003) than the no FOG group. Longer disease duration was associated with the responsive group compared to the no FOG group (p = .002). The unresponsive FOG group had significantly poorer visuospatial ability (p = .001) and executive functioning (p = .02) than both the no and responsive FOG subgroups. These latter groups were not significantly different. The responsive FOG group was associated with the presence of hallucinations.

CONCLUSION

Aside from pharmacological differences, unresponsive FOG is associated with executive and visuospatial dysfunction implicating frontostriatal pathways while responsive FOG is associated with hallucinations suggesting involvement of posterior cortical regions. Further study and treatment of FOG should include appropriate subtype classification.