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.

Pro-inflammatory diets may objectively negatively impact sleep amongst police officers

1. This study showed that more pro-inflammatory diets led to higher wake-after-sleep-onset (WASO) amongst police officers, indicating increased sleep fragmentation and poor sleep.

2. Contrarily, a more pro-inflammatory diet was associated with improved subjective sleep quality in police officers.

Evidence Rating Level: 2 (Good)

Approximately 30% of individuals in the United States receive less than 7 hours of sleep daily, as recommended by the National Sleep Foundation. An even greater percentage experience insomnia or sleep apnea. Diet is of particular importance to sleep, with pro-inflammatory diets (such as a Western diet) affecting sleep. Furthermore, shift work has long been associated with sleep disturbances and ingesting pro-inflammatory diets, such as seen in police officers. In this observational cohort study, longitudinal and cross-sectional associations between inflammatory diet and sleep quality were examined amongst police officers.

Active-duty police officers were recruited from New York, United States of America. Baseline visits occurred between 2004 and 2009 (n=646), with follow-up visits between 2011 and 2015 (n=281) and 2015 and 2019 (n=240). Officers completed a food frequency questionnaire (FFQ) that determined their frequency of consumption of 144 different foods and beverages. The Dietary Inflammatory Index (E-DII) was utilized to measure the pro- or anti-inflammatory nature of a particular diet, with higher scores indicating a more-proinflammatory diet. Furthermore, objective sleep duration and subjective sleep quality were measured through several perimeters, such as sleep efficiency, wake-after-sleep-onset (WASO), and sleep latency (time between lying down and sleep onset).

Results demonstrated that every 1-unit increase in EDII (ie more pro-inflammatory diet) was associated with increased WASO (an objective indicator of poorer sleep and sleep fragmentation) in both night-shift and day-shift officers. Interestingly, more pro-inflammatory diets were associated with improved subjective sleep quality. However, this study was limited as the sample was mainly European-American males, thus limiting generalizability. Nonetheless, this study was significant in highlighting the bidirectional relationship between inflammation and sleep in police officers, which may be a target for future interventional studies.

Risk of chronic kidney disease progression may be greater amongst patients with obstructive sleep apnea

1. This study found moderate-to-very high risk of chronic kidney disease progression was greater in patients with more severe obstructive sleep apnea based on eGFR and ACR measurements.

2. Furthermore, many patients with increased risk of chronic kidney disease progression were unaware of their abnormal kidney function.

Evidence Rating Level: 2 (Good)

Chronic Kidney Disease (CKD) affects more than 10% of the global population and has been shown to lead to cardiovascular disease and mortality. While substantial medical literature supports a bi-directional relationship between CKD and obstructive sleep apnea (OSA), significant gaps still exist in our understanding. In this observational cohort study, the prevalence and awareness of CKD progression was assessed in OSA patients.

In this study, 1295 patients (≥18 years old) referred to one of five Canadian academic sleep centers for suspected OSA were included. Patients who were currently on dialysis and/or had a prior kidney transplant were excluded. Patients were further categorized as having, no/mild OSA, moderate OSA, or severe OSA, based on oxygen desaturation index. The patients were asked to complete a sleep questionnaire and a home sleep apnea or in-lab polysomnography test. Blood and urine samples were collected from each patient for albumin:creatinine ratio (ACR) and estimated glomerular filtration rate (eGFR) measurements. The risk of CKD progression was determined from heat maps generated from eGFR and ACR levels.

In this study, 13.6% of the no/mild OSA group, 28.9% of the moderate OSA group, and 30.9% of the severe OSA group had a moderate-to-very high risk of CKD progression. Compared to patients with no/mild OSA, the odds ratio for moderate-to-very high risk of CKD progression was 2.63 for moderate OSA and 2.96 for severe OSA patients. Interestingly, 73% of patients with increased risk of CKD progression were unaware they had abnormal kidney function. However, this study was limited in that the results were self-reported by the patients, which may be confounded by poor memory commonly found amongst OSA patients. Nonetheless, this study was significant in suggesting patients with moderate to severe OSA may be at increased risk for CKD progression, which patients may be unaware of.

Poor sleep quality and pandemic-related perceived threat may exacerbate post-traumatic stress disorder symptoms

1. In this study, baseline poor sleep was associated with more severe PTSD symptoms longitudinally.

2. Furthermore, this relationship between poor sleep and more severe PTSD symptoms was moderated by perceived pandemic-related threat.

Evidence Rating Level: 2 (Good)

The COVID-19 pandemic has claimed over 4 million lives globally and heightened levels of stress, psychiatric, and post-traumatic stress disorder (PTSD) symptoms among individuals. Poor sleep quality and perceived threat have been shown to contribute to and worsen PTSD symptoms. Furthermore, poor sleep quality may be of particular importance in the context of perceived threat. This observational study investigated associations between self-reported sleep quality and anticipated threat appraisals of the pandemic among adults with PTSD for 6 months.

In this study, 590 adult participants affected by trauma and PTSD were included from all 50 states in the United States of America through online forums. PTSD symptoms and their severity levels were assessed at baseline and after 30 days (via 20 items PTSD Checklist-5) for the participants; the same longitudinal evaluation was performed for sleep quality. Participants further rated the threat of the pandemic to domains of life such as work and finances, education and training, social relationships inside and outside the home, and physical and emotional health in the next 12 months.

Results demonstrated that participants generally rated their sleep quality as “fair” at baseline. They also reported mild to moderate anticipatory threat appraisals of the pandemic at baseline. However, worse baseline sleep quality correlated with more severe PTSD symptoms at the 30-day follow-up, particularly in those who perceived the pandemic as particularly threatening. However, this study was limited in that survey data was obtained at two time points with a large number of participants not providing follow-up data, raising concerns regarding generalizability of results. Nonetheless, this study was significant in that it was the first to examine the longitudinal relationship between, sleep quality, PTSD, and perceived threat during the COVID-19 pandemic.

Image: PD

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