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.

Sleep deprivation may affect next day performance in endurance activities and feelings of exhaustion.

1. Athletes randomized to partial sleep deprivation demonstrated a quicker time to exhaustion affecting their overall physical performance in running exercises.

2. Sleep deprived athletes did not differ significantly from the control group in terms of maximal voluntary isometric contraction after performing strength exercises.

Evidence Rating Level: 2 (Good)

Sleep deprivation is known to limit recovery, thus affecting physical performance as early as the following day. This phenomenon is particularly pronounced in athletes, who are commonly required to perform strenuous exercise, often on consecutive days. There is a paucity in research in this population to determine the impact of sleep deprivation after exercise.

This randomized controlled trial enrolled 11 male athletes who followed a regular sleep schedule to examine the effect of partial sleep deprivation (PSD) after exercise, on exercise performance and metabolic responses the next morning. Participants were randomized to either control (slept from 23:00-07:00) or PSD (normal sleep duration was shortened by 40%). Participants first completed an exercise protocol on day one. The following morning, maximal voluntary isometric contraction (MVC), physiological measures after a 20 min submaximal run at 75% maximal oxygen uptake (VO_2max), and time to exhaustion (TTE) at 85% VO_2max were assessed.

Results demonstrated a significant decrease in carbon dioxide output (VCO2) and respiratory exchange ratio (RER) in PSD participants compared to control after a 20 min submaximal run at 75% VO_2max. Furthermore, TTE was significantly shorter in the PSD group compared to control at 85% VO_2max. However, MVC and oxygen uptake (VO₂) kinetics did not differ significantly between the two groups on day two. Limitations of this study include lack of objective measurements of muscle glycogen content and of overall sleep quality. There were also no female participants which limits generalizability of results. Nonetheless, the findings of this study are significant and suggest the benefit of flexible training programs in the instance of sleep deprivation.

Sleep and pain may share a bi-direction relationship amongst patients with chronic musculocutaneous pain

1. Increased current diurnal pain affected quality of sleep and total sleep time the following night amongst patients with chronic musculocutaneous pain.

2. Seasonality and fluctuations in mental distress did not impact the relationship between pain and sleep on a day-to-day basis amongst patients with chronic musculocutaneous pain.

Evidence Rating Level: 2 (Good)

Numerous studies have provided evidence for a bi-directional relationship between pain and sleep. However, there is a paucity in research with respect to day-to-day associations between pain and sleep, and how additional factors such as seasonality may affect this relationship. This prospective cohort study sought to examine the bi-directional relationship between pain and sleep on a day-to-day basis amongst patients with chronic primary musculocutaneous pain (CMP). How seasonality (summer vs. winter) or daily fluctuations in mental distress affected this relationship was also studied. 56 patients aged 18-65 years with CMP were enrolled from the Rehabilitation Department or Pain Clinic at the University Hospital of North Norway. Patients with major medical conditions, neurological conditions, or had a diagnosis of sleep disorders other than insomnia were excluded. Primary outcomes assessed for sleep indices (subjective measures of sleep quality obtained via questionnaires, objective measures of sleep via actigraphy) and pain measures [via the Brief Pain Inventory (BPI)].

The study’s main finding demonstrated that current pain was a significant predictor of poor next-night sleep quality. It was also suggested that current pain marginally impacted next-night sleep duration. Inversely, sleep quality was found to have some effect on reported pain the subsequent day. Furthermore, mental distress and seasonality did not impact the day-to-day relationship between sleep and pain. Limitations included small sample size which underpowered the study, and that medication use was not recorded or adjusted for in analysis. Nonetheless, this study was significant in re-iterating the importance of evaluating sleep in chronic pain patients, and how influential sleep and pain are amongst each other.

Improved sleep quality reduced cardio-metabolic risk factors

1. In this study, improved sleep quality was associated with significantly decreased systolic blood pressure and increased high-density lipoprotein levels after 24 months.

2. Increased time to sleep was also associated with decreased low-density lipoprotein levels, after 24 months.

Evidence Rating Level: 1 (Excellent)

Sleep has endocrinologic implications, which may impact cardio-metabolic health. However, sleep is not a well-recognized target for intervention when managing risk factors for cardio-metabolic disease. The MODERN trial (Management to Optimize Diabetes and mEtabolic syndrome Risk reduction via Nurse-led interventions) was designed to assess the impact of implementing lifestyle modifications on sleep quality and quantity, and thus cardio-metabolic risk factors, after 24 months.

This randomized controlled trial randomized 121 participants aged between 40-70 years from Colac or Shepparton, Australia who possessed 3 or more measurable cardio-metabolic risk factors (ex. hypertension, hyperglycemia, dyslipidemia). 59 participants were randomized to a lifestyle and health intervention group (received more individualized education, a physical activity program, and counselling on diet medication use), and 62 were randomized to a usual care group. Participants were excluded if they had a clinically established cardiovascular disease, life-threatening co-morbidities, or had renal disease. Primary outcomes assessed objective and subjective measures of diet, sleep (via actigraphy), physical activity, and cardio-metabolic risk (ex. blood pressure, blood glycemic levels).

Results at 24 months showed that both groups had improved markers of cardio-metabolic risk factors, with a greater reduction in blood pressure in the intervention group. Results also demonstrated that improved sleep efficiency significantly decreased systolic blood pressure and increased high-density lipoprotein levels. Furthermore, an increase in total sleep time significantly decreased low-density lipoprotein levels. Limitations were noted in the study, such as the use of actigraphy to assess sleep instead of polysomnography (the gold standard). Furthermore, this study sampled participants with normal sleep profiles, and therefore may not be generalizable to those who sleep poorly. Nonetheless, this study showed that improvements in sleep quality were associated with improved cardio-metabolic risk factors.

Image: PD

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