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.

Aerobic exercise after 2 PM did not affect sleep amongst people with depression

1. In this study, aerobic exercise performed after 2 PM did not negatively impact subsequent night’s sleep amongst participants with unipolar depression.

2. Aerobic exercise improved mood and decreased depressiveness and anger amongst participants with depression.

Evidence Rating Level: 1 (Excellent)

Due to the strong relationship between insomnia and depression, insomnia may be targeted for treatment in people with depression. Sleep hygiene guidelines recommend aerobic exercise as a meaningful strategy to counter insomnia prior to 2 PM, which may also improve mood. However, these guidelines also suggest strenuous physical activity after 2 PM may also aggravate insomnia due to endorphin release. The primary goal of this study was to assess the effect of a single session of aerobic exercise on subsequent night’s sleep amongst participants with depression.

This two-arm parallel-group, randomized control trial enrolled 92 participants aged 18-65 years diagnosed with unipolar depression from a psychosomatic in-patient rehabilitation unit in St. Gallen, Switzerland. 46 participants were randomized to an exercise group (aerobic exercise performed at 16:45), whereas 46 participants were randomized to a control group (no exercise). Participants using medications such as hypnotics and opioids, had moderate obstructive sleep apnea, or BMI >40 were excluded. Primary outcome assessed for sleep efficiency using polysomnography. Secondary outcomes assessed for subjective measures such as sleep quality and mood state using questionnaires.

Results demonstrated that exercise after 2 PM did not significantly affect sleep efficiency, daytime sleepiness, or other subjective sleep parameters. However, participants in the exercise group did report an immediate positive effect on mood state (less agitation, depressiveness, and anger, as well as  increased levels of activation, elation, and calmness). This study was limited due to its stringent exclusion criteria (such as participant use of hypnotics) and polysomnographic montage, which restrict generalizability of results. Nonetheless, this study was significant in suggesting that physical activity after 2 PM improved mood state and did not negatively affect sleep.

Sleep problems more frequent amongst women in gender comparison during COVID-19 pandemic

1. In this systematic review and meta-analysis, women exhibited a greater prevalence of sleep problems across genders during the COVID-19 pandemic.

2. In a subgroup analysis, there was a lower rate of sleep problems in regions where lockdown was implemented, compared to regions where only control measures without lockdown were in place.

Evidence Rating Level: 1 (Excellent)

Current literature suggests COVID-19 has introduced and possibly exacerbated sleep problems. However, no empirical studies have been performed comparing sleep problems across genders during the COVID-19 pandemic, which is important to elucidate when considering treatment options. This study aimed to shed light on the prevalence of sleep problems across genders during the COVID-19 pandemic.

This systematic review and meta-analysis included 99 papers (54 papers in female subgroup and 45 papers in male subgroup) after screening and full text-review for eligibility criteria. Studies with primary outcomes assessing for sleep problems (defined as insomnia symptoms and poor sleep quality) during the COVID-19 pandemic (December 2019 to February 2021) were included. No limitations were imposed regarding participant characteristics. Primary outcome assessed for prevalence of gender-specific sleep problems (assessed using varied survey instruments) during the COVID-19 pandemic.

Results found that females had a higher pooled estimated prevalence of sleep problems (41%) in comparison to men (31%). In subgroup analysis, the prevalence of sleep problems was higher amongst patients infected with COVID-19 compared to other subgroups. Furthermore, the prevalence of sleep problems was lower in regions where lockdown was implemented in comparison to regions where other control measures were in place, and such regardless of gender. This study was limited due to the subjective measure of sleep problems, which was self-reported. Furthermore, papers using varied sleep problem survey instruments were included in this study, which made it difficult to capture the heterogenous nature of sleep problems. Nonetheless, these findings suggest that COVID-19 related events and restrictions have impacted sleep, which imposed a greater effect on women in cross-gender analysis and should be a target for future treatment.

Pain and sleep seem to have a bidirectional causal relationship

1. Genetic proxy to insomnia was a risk factor and increased the odds of reporting pain amongst patients in this study across all pain categories (chronic or acute).

2. Conversely, results demonstrated pain to have a lesser, but still a significant effect on insomnia symptoms.

Evidence Rating Level: 1 (Excellent)

Many individuals with chronic pain have reported sleeping disorders, such as insomnia. There appears to be a relationship between insomnia and pain; however, the quality and details of this relationship have yet to be established. Genome-wide association studies (GWASs) allow scientists to identify single-nucleotide polymorphisms (SNPs) and other variants in DNA associated with a disease. The Mendelian method allows more in-depth study of genes and how exposures can influence their expression. Furthermore, two-sample Mendelian randomization allows to better observe causality between 2 conditions or diseases using genetic information. The aim of this study was to establish a causal bilateral relationship and possible causality between insomnia and pain.

In this study, two-sample Mendelian randomization analysis was conducted using genetic information from biobanks. Genetic information on pain was drawn from a Finnish biobank with patients who carried an ICD 10 diagnosis code for disorders with an obvious pain component. The genetic pool for insomnia problems was gathered from a British biobank and 23andMe, in which the diagnosis was self-reported. Two-sample Mendelian randomization analysis allowed to establish which SNPs were significant for pain and insomnia, while further Mendelian randomization analysis allowed to correlate insomnia and pain symptoms with genetic data.

This study showed a bidirectional relationship between insomnia and pain. Symptoms of insomnia acted as a risk factor for developing pain of any subtype: abdominal, general, and articular. Furthermore, pain was shown to have a smaller but significant effect on insomnia symptoms. The results of this study should be taken into consideration while acknowledging its limitations. This study used pain diagnosis data from a data subset that did not differentiate chronic from acute pain, which should be considered when interpreting results. Nonetheless, this study was significant in elucidating a causal relationship between insomnia and pain, suggesting further treatment strategies.

Image: PD

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