Wellness Check: Sleep

2 Minute Medicine is pleased to announce that we are launching Wellness Check, a new series dedicated to exploring new research evidence focused on wellness. Each week, we will report on articles examining different aspects of wellness, including (but not limited to) nutrition, sleep, reproductive health, substance use and mental health. This week, we explore the latest evidence-based updates in sleep. 

Mental health in young adults may be linked to sleep chronotype

1. Young adults with evening chronotypes recorded higher depression and anxiety scores, and poorer sleep quality in comparison to morning and intermediate chronotypes.

2. Positive psychological traits, such as mindfulness and positive social interactions, were more frequently reported by individuals with morning chronotypes.

Evidence Rating Level: 2 (Good)

Circadian rhythm preferences, also known as chronotypes, impact physical and mental performance. Previous studies have found an association between chronotype and psychological traits, sleep disturbances, and social support. In general, evening chronotypes disclose more negative psychological traits and are more prevalent in young adults, whereas morning and intermediate chronotypes report better social support and more mindfulness.

In this study, 3160 young adults attending Memorial University, Newfoundland, Canada, completed an online questionnaire related to demographics and sleep chronotype. Inclusion criteria were limited to attending university students aged 18-35 years. The questionnaire incorporated existing scales and survey instruments (ex. Morningness-Eveningness questionnaire and the Pittsburg Sleep Quality index) to assess for sleep chronotype, symptoms of anxiety and depression, mindfulness, sleep quality, and social support. The main objective of the study was to determine the relationship between sleep chronotype, sleep quality, and psychological factors. Furthermore, the study explored the relationship between sleep chronotype and social support level.

The results of this study demonstrated that there was an association between age and chronotypes: evening chronotypes were often younger adults, and morning types were older adults. Furthermore, compared to other chronotypes, students with evening chronotypes showed higher levels of depression, anxiety, and worsened sleep quality. In contrast, students with morning chronotypes were more likely to report greater levels of mindfulness and social support. The results of this study should be taken into consideration while acknowledging some of its limitations. For instance, data was self-reported via questionnaire, and female and Caucasian students were overrepresented in the sample. Nonetheless, this study underlined the possible issues experienced by young adults with evening sleep chronotypes, which should be considered in clinical practice.

Sleep quality during pregnancy may help predict emotional distress in postpartum period

1. In this study, first time mothers with longer sleep time during pregnancy were less likely to report high levels of anxiety and depression in the postpartum period.

2. Higher diary-based wake after sleep onset (ie. lower sleep quality) at 3 months post-partum predicted more moderate anxiety and depression symptoms compared to low symptomology.

Evidence Rating Level: 2 (Good)

Sleep and mental health are strongly interrelated. Pregnancy and postpartum periods are times when sleep disturbances and mood fluctuations are common. Considering sleep is a modifiable risk factor, this study aimed to determine if sleep quantity and quality during pregnancy predict emotional distress during the postpartum period.

In this study, 215 nulliparous couples residing in Israel with a singleton, full term pregnancy and a healthy infant were voluntarily recruited. Couples with a preterm delivery, multiple gestations, and unhealthy newborns were excluded. The study required five home visits: the first in the third trimester of pregnancy, and the remainder at 3-,6-,12-, and 18-months postpartum. Study outcomes of sleep duration and quality [measured via wake time after sleep onset (WASO)] were recorded by actigraphy (objective measure) and diary recording (subjective measure). Furthermore, mothers completed questionnaires related to depression (Edinburgh Postnatal Depression Scale) and anxiety (Beck Anxiety Inventory) at all five time points.

Results indicated that women could be categorized into 4 classes of symptoms: high comorbidity (5.4%), moderate comorbidity (19.4%), low anxiety and decreasing depression symptomology (18.6%) and low symptomology (56.6%). Overall, mothers during pregnancy with shorter sleep durations were more likely to fall in the high or moderate comorbidity groups. Furthermore, higher WASO (ie lower sleep quality) scores at three months post-partum were more likely to be classified as having moderate symptomology compared to low symptomology. However, this study was limited in that data was collected in a homogenous, highly educated, two parent family community. Nonetheless, this study contributes to understanding and demonstrating the relationship between sleep and mood, which would be an important subject to address in clinical setting during pregnancy and the post-partum periods.

An after-lunch nap or light exposure may increase cognitive abilities

1. In this study, students who took a nap after lunch felt happier, more vital, self-controlled, and less sleepy when performing cognitive tasks. 

2. Amongst students exposed to bright light, there was an improvement in their working memory in a time-dependent fashion.

Evidence Rating Level: 2 (Good)

Naps and bright light exposure have been labeled as effective strategies to counter the mental fatigue associated in the afternoon, termed the “after-lunch dip”. Literature also suggested that they may impact different cognitive domains. This study aimed to investigate the effects of an after-lunch nap and bright light exposure on different cognitive domains and whether their effects were persistent over time.

Twenty healthy students who had the habit of napping midday were recruited and assessed for sleep chronotypes and disturbances, as well as physical and mental health. Students were randomized to one of three interventions held between 1:00 and 1:40 PM: bright light (at eye level), nap (in the dark), or control. Study outcomes evaluated sustained attention with a visual psychomotor vigilance task, response inhibition with a go-no-go task, and working memory with a paced visual serial addition task. Furthermore, all students completed questionnaires on subjective sleepiness, mood, vitality, and self-control. A repeat session was conducted to assess the persistent effects of bright light and napping

Students who napped reported less sleepiness, and more vitality which persisted up to 2 hours after the intervention. Furthermore, students in the nap group showed significant improvement in response inhibition and working memory in comparison to the 2 other groups. Interestingly, students exposed to bright light demonstrated improved working memory time-dependently, with a higher reaction speed in only the first session. No intervention showed improvement of sustained attention. However, this study was limited in that there were no baseline measure of cognitive assessment, and the study group was considerably homogenous. Nonetheless, this study shows that napping mid-day or self -exposure to bright light may improve task performance in various cognitive domains.

Image: PD

©2021 2 Minute Medicine, Inc. All rights reserved. No works may be reproduced without expressed written consent from 2 Minute Medicine, Inc. Inquire about licensing here. No article should be construed as medical advice and is not intended as such by the authors or by 2 Minute Medicine, Inc.