The latest medical research on Sleep Medicine

The research magnet gathers the latest research from around the web, based on your specialty area. Below you will find a sample of some of the most recent articles from reputable medical journals about sleep medicine gathered by our medical AI research bot.

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ACE2 expression is elevated in airway epithelial cells from older and male healthy individuals but reduced in asthma.


COVID-19 is complicated by acute lung injury, and death in some individuals. It is caused by SARS-CoV-2 that requires the ACE2 receptor and serine proteases to enter AEC. We determined what factors are associated with ACE2 expression particularly in patients with asthma and COPD.

We obtained lower AEC from 145 people from two independent cohorts, aged 2-89 years, Newcastle (n = 115) and Perth (n = 30), Australia. The Newcastle cohort was enriched with people with asthma (n = 37) and COPD (n = 38). Gene expression for ACE2 and other genes potentially associated with SARS-CoV-2 cell entry was assessed by qPCR, and protein expression was confirmed with immunohistochemistry on endobronchial biopsies and cultured AEC.

Increased gene expression of ACE2 was associated with older age (P = 0.03) and male sex (P = 0.03), but not with pack-years smoked. When we compared gene expression between adults with asthma, COPD and healthy controls, mean ACE2 expression was lower in asthma patients (P = 0.01). Gene expression of furin, a protease that facilitates viral endocytosis, was also lower in patients with asthma (P = 0.02), while ADAM-17, a disintegrin that cleaves ACE2 from the surface, was increased (P = 0.02). ACE2 protein expression was also reduced in endobronchial biopsies from asthma patients.

Increased ACE2 expression occurs in older people and males. Asthma patients have reduced expression. Altered ACE2 expression in the lower airway may be an important factor in virus tropism and may in part explain susceptibility factors and why asthma patients are not over-represented in those with COVID-19 complications.

Reduced sympatho-vagal responses to orthostatic stress in drug naïve idiopathic restless legs syndrome.

J Clin Sleep

Restless legs syndrome (RLS) is known to be a risk factor for cardiovascular disease (CVD). However, there are no electrophysiological biomarkers to assess this risk. This study aimed to evaluate the heart rate variability (HRV) and cardiovascular reflexes in the supine and standing positions during wakefulness in patients with RLS.

Fourteen drug-naïve RLS patients (12 women and 2 men, mean age 42.14 ± 7.81 years) and 10 healthy controls underwent tests for blood pressure, heart rate when in the supine and standing positions, and deep breathing and handgrip tests in controlled laboratory conditions. Data on five-minute R-R intervals at each position were collected and analyzed for HRV.

Expected cardiovascular reflexes were within the normal range, and were similar between the two groups. In HRV analysis, normalized unit of the low frequency component and low frequency/ high frequency (LH/HF) ratio during standing were lower in RLS patients than in the controls. The LF/HF ratio responses during change from supine to standing positions were significantly reduced in RLS patients (RLS patients: mean ± SD, 2.94 ± 3.11; controls: 7.51 ± 5.58, P = 0.042.) On spearman's rank correlation, questionnaires related sleep problems were associated with the parameters of HRV.

RLS patients showed reduced sympatho-vagal responses during change from supine to upright positions during wakefulness, and RLS related sleep disturbance was a contributing factor for autonomic nervous system dysfunction. This case-control study demonstrated a difference in HRV response to position change in a considerably small group of RLS patients. The relevance of this finding is uncertain, but it may be worthy of further investigation in longitudinal studies on RLS and cardiovascular disease.

The accuracy of the THIM wearable device for estimating sleep onset latency.

J Clin Sleep

THIM is a wearable device designed to accurately estimate sleep onset. This article presents two studies that tested the original (Study 1) and a refined (Study 2) THIM sleep onset algorithms compared to polysomnography (PSG).

Twelve (Study 1) and twenty (Study 2) individuals slept in the laboratory on two nights where participants underwent THIM-administered sleep onset trials with simultaneous PSG recording. Participants attempted to fall asleep whilst using THIM, which woke them once it determined sleep onset.

In Study 1, there was no significant difference between PSG (Mean, M = 1.94 min, SD = 1.32) and THIM-sleep onset latency (M = 2.05 min, SD = 1.38) on the first or second night, p > .07. There were moderate correlations between PSG and THIM on both nights, r(s) > .57, p < .001. On 23.74% of trials, PSG-sleep onset could not be determined before THIM ended the trial. With a revised THIM algorithm in Study 2, there was no significant difference between PSG (M = 3.41 min, SD = 2.21) and THIM-sleep onset latency (M = 3.65 min, SD = 2.18), p = .25, strong correspondence between the two devices, r(s) > .73, p < .001, narrow levels of agreement on Bland-Altman plots, and significantly less trials where PSG-sleep onset had not occurred (10.24%), p = .04.

THIM showed a high degree of correspondence and agreement with PSG for estimating sleep onset. Future research will investigate whether THIM is accurate with an insomnia sample for clinical purposes.

Sex differences in deterioration of sleep properties associated with aging: a 12-year longitudinal cohort study.

J Clin Sleep

The sleep patterns of humans are greatly influenced by age and sex and have various effects on overall health as they change continuously during the lifespan. We investigated age-dependent changes in sleep properties and their relation to sex in the middle-aged.

We analyzed data from 2640 participants (mean age of 49.8 ± 6.8 years at baseline, 50.6% women) in the Korean Genome and Epidemiology Study, which assessed sleep habits using the Pittsburgh Sleep Quality Index (PSQI) and other clinical characteristics. We analyzed the sleep habit changes that occurred between baseline and a follow-up point (mean interval 12.00 ± 0.16 years). Associations of age and sex with nine sleep characteristics were evaluated.

Age was associated with most of the sleep characteristics cross-sectionally and longitudinally (p<0.05), except for the time in bed (TIB) at baseline (p=0.455) and Δsleep duration (p=0.561). Compared to men, women had higher PSQI scores, shorter TIB, shorter sleep duration, and longer latency at baseline (p≤0.001). Longitudinal deterioration of PSQI score, habitual sleep efficiency (HSE), duration, and latency was more prominent in women (p<0.001). The sex differences in these longitudinal sleep changes were mainly noticeable before the age of 60 (p<0.05). Worsening of PSQI scores, HSE, and latency was most evident in peri-menopausal women. Men presented with larger advancement of chronotype (p<0.001), with the peak sex-related difference occurring in the late 40s (p=0.048).

Aging is associated with substantial deterioration in sleep quantity and quality as well as chronotype advancement, with the degree and timing of these changes differing by sex.

Identifying predictive factors for sleep bruxism severity using clinical and polysomnographic parameters: a principal component analysis.

J Clin Sleep

The aim was to identify predictive factors of sleep bruxism (SB) severity among polysomnographic (PSG) parameters, salivary cortisol levels, temporomandibular disorders, age and sex.

Young adults (19-30y) were screened for self/roommate reports of teeth grinding/clenching during sleep associated to clinical signs of tooth wear. Positive individuals for both conditions were submitted to PSG exam to provide a definite diagnosis of SB (n=28). Healthy participants without SB signs/symptoms were also included (n=15). The Research Diagnostic Criteria/TMD was applied to determine functional, muscular and articular domains of the Temporomandibular Index. Cortisol awakening levels were measured in saliva. Principal component analysis (PCA) was used to extract the latent components emerging from PSG results and two regression models were adjusted to predict the number and duration of bruxism episodes.

PCA resulted in four components, C1: %N1, total sleep time, sleep efficiency, arousals/micro-arousals; C2: %N2, %N3; C3: periodic limb movements and apneas; C4: %REM and REM latency. The number of SB episodes/h was predicted by increasing muscular scores and Component 2 (decrease in %N2 and increase in %N3) (adjR2=45%; p=0.001). The total time of SB episodes was predicted by decreased articular and increased functional scores, age and female sex (adjR2=36%; p=0.010). Salivary cortisol levels were not associated to SB severity and did not differ between groups.

The findings showed that SB severity was predicted by muscular and functional scores, female sex and distinct PSG patterns, contributing to deepen the knowledge of the underlying pathophysiology of SB severity; additionally, they can help to formulate specific health approaches for the patient to better assist this condition.

Central airway collapse is related to obesity independent of asthma phenotype.


Late-onset non-allergic asthma in obesity is characterized by an abnormally compliant, collapsible lung periphery; it is not known whether this abnormality exists in proximal airways. We sought to compare collapsibility of central airways between lean and obese individuals with and without asthma.

A cross-sectional study comparing luminal area and shape (circularity) of the trachea, left mainstem bronchus, right bronchus intermedius and right inferior lobar bronchus at RV and TLC by CT was conducted.

In 11 lean controls (BMI: 22.4 (21.5, 23.8) kg/m2 ), 10 lean individuals with asthma (23.6 (22.0, 24.8) kg/m2 ), 10 obese controls (45.5 (40.3, 48.5) kg/m2 ) and 21 obese individuals with asthma (39.2 (35.8, 42.9) kg/m2 ), lumen area and circularity increased significantly with an increase in lung volume from RV to TLC for all four airways (P < 0.05 for all). Changes in area and circularity with lung volume were similar in obese individuals with and without asthma, and both obese groups had severe airway collapse at RV. In multivariate analysis, change in lumen area was related to BMI and change in circularity to waist circumference, but neither was related to asthma diagnosis.

Excessive collapse of the central airways is related to obesity, and occurs in both obese controls and obese asthma. Increased airway collapse could contribute to ventilation abnormalities in obese individuals particularly at lower lung volumes, and complicate asthma in obese individuals.

Endobronchial coil spring fiducial markers for CyberKnife® stereotactic body radiation therapy.


SBRT is an alternative treatment for early-stage inoperable lung cancer. Metallic FM allow to increase tumour tracking precision by CyberKnife®. Currently used techniques for FM placement have many limitations; transthoracic insertion has a high risk for pneumothorax, endovascular insertion requires expertise and dedicated angiography infrastructure and endobronchial linear-gold FM dislocate frequently. This is the first study to assess the safety and efficacy of cs-FM endobronchial insertion under fluoroscopy with or without R-EBUS assessment.

We retrospectively evaluated all consecutive patients undergoing endobronchial cs-FM placement for at least one PPL <25 mm between 10.2015 and 12.2019. TBB of the PPL were performed in case of a typical R-EBUS signal. PPL tracking accuracy by CyberKnife, complications, cs-FM migration rate and procedure duration were analysed.

A total of 52 patients were treated during 55 procedures and 207 cs-FM were placed in 70 PPL. Tracking was successful for 65 of 70 (93%) PPL. R-EBUS was performed for 33 (47%) PPL and TBB for 9 (13%) PPL. Bronchospasm occurred once and any other complications were observed. Migration of cs-FM occurred in 16 of 207 (8%) cs-FM. Migration was more frequent when the target was in a previously irradiated area (P = 0.022). The median bronchoscopy duration was 31.5 min (n = 48 procedures).

Bronchoscopic cs-FM placement is a rapid and safe procedure. It is associated with a low migration rate and allows precise SBRT delivery. Previous irradiation of the PPL was associated with a higher migration rate.

Infection risk in sarcoidosis patients treated with methotrexate compared to azathioprine: A retrospective 'target trial' emulated with Swedish real-world data.


No clinical trial has examined the risk of infection associated methotrexate and azathioprine, two advocated treatments for sarcoidosis. We aimed to compare the 6-month risk of infection after the initiation of methotrexate or azathioprine.

We conducted a retrospective target trial emulation using Swedish pre-existing data. We searched for eligible participants who were dispensed methotrexate or azathioprine in the Prescribed Drug Register (PDR) every day between January 2007 and June 2013. Adults were eligible if they had ≥2 ICD-coded visits for sarcoidosis in the National Patient Register (NPR) and were dispensed ≥1 systemic corticosteroid but no methotrexate or azathioprine in the past 6 months (PDR). Within 6 months of methotrexate or azathioprine initiation, diagnosis of infectious disease was identified (visit in the NPR where infectious disease was the primary diagnosis). We estimated RR and risk differences comparing methotrexate (n = 667) to azathioprine initiations (n = 259) using targeted maximum likelihood estimation (TMLE) adjusting for demographic factors, comorbidity and sarcoidosis severity proxies.

There were 43 infections in the methotrexate group (adjusted 6-month risk 6.8%) and 29 infections in the azathioprine group (12.0%). The RR for infectious disease at 6 months associated with methotrexate compared to azathioprine initiation was 0.57 (95% CI: 0.39, 0.82) and the risk difference was -5.2% (95% CI: -8.5%, -1.8%). The RR at 9 months was attenuated to 0.77 (95% CI: 0.52, 1.14).

Methotrexate appears to be associated with a lower risk of infection in sarcoidosis than azathioprine, but randomized trials should confirm this finding.

Insomnia in patients with coronary heart disease: prevalence and correlates.

J Clin Sleep

To determine the prevalence of insomnia and its association with clinical and psychosocial factors in a large sample of outpatients with coronary heart disease (CHD).

The sample comprised 1082 patients, mean age 62 years (21% female), who participated in the cross-sectional NORwegian CORonary Prevention Study. Patients who were hospitalized with myocardial infarction and/or a coronary revascularization procedure in 2011-14 responded to a self-report questionnaire and participated in a clinical examination with blood samples 2-36 (mean 16) months later. Insomnia was assessed using the Bergen insomnia scale, a questionnaire based on the criteria for the clinical diagnosis of insomnia described in the Diagnostic and Statistical manual, 4th version (DSM-IV-TR). We performed bivariate logistic regressions for crude analysis and backwards stepwise logistic regressions for multi-adjusted odds ratios.

In total, 488 patients (45%) reported insomnia and 24% of these patients used sleep medication in the previous week. Anxiety symptoms (OR: 5.61) were the strongest determinants of insomnia, followed by female sex (OR: 1.88), diabetes (OR: 1.83), eating fish less than 3 times a week (OR: 1.69), type D personality (OR: 1.69), and CRP ≥2 mg/L (OR:1.58), in multi-adjusted analyses.

Insomnia was highly prevalent in CHD outpatients. Both psychological factors, lifestyle factors and subclinical inflammation were associated with insomnia. Our results emphasize the need to identify patients with insomnia and provide appropriate management of insomnia in outpatients with CHD.

Effects of obstructive sleep apnea on human spatial navigational memory processing in cognitively normal older individuals.

J Clin Sleep

Obstructive sleep apnea (OSA) prevalence increases with age, but whether OSA-related sleep disruption could interrupt the processing of previously encoded wake information thought to normally occur during sleep in cognitively normal older adults remains unknown.

Fifty-two older (age = 66.9 ± 7.7 years, 56 % female), community-dwelling, cognitively normal adults explored a 3D maze environment and then performed 3 timed trials before (evening) and after (morning) sleep recorded with polysomnography (PSG) with a 20-minute morning psychomotor vigilance test (PVT).

Twenty-two (22) subjects had untreated OSA (Apnea Hypopnea Index (AHI4%) ≥ 5/hour) where severity was mild on average [median (interquartile range (IQR))] AHI4% = 11.0 (20.7)/hour) and 30 subjects had an AHI4% < 5/hour. No significant differences were observed in overnight percent change in completion time or in the pattern of evening pre-sleep maze performance. However, during the morning post-sleep trials, there was a significant interaction between OSA group and morning trial number such that participants with OSA performed worse on average with each subsequent morning trial, whereas those without OSA showed improvements. There were no significant differences in morning PVT performance suggesting that vigilance is unlikely to account for this difference in morning maze performance. Increasing relative frontal slow wave activity (SWA) was associated with better overnight maze performance improvement in participants with OSA (r= 0.51, p = 0.02) but not in those without OSA, and no differences in slow wave activity were observed between groups.

OSA alters morning performance in spatial navigation independent of a deleterious effect on morning vigilance or evening navigation performance. Relative frontal slow wave activity is associated with overnight performance change in older subjects with OSA, but not those without.

Average volume-assured pressure support versus conventional bilevel pressure support in pediatric nocturnal hypoventilation: a case series.

J Clin Sleep

Average volume-assured pressure support (AVAPS) is a modality of non-invasive ventilation (NIV) that provides a targeted tidal volume by automatically adjusting the inspiratory pressure support within a set range. Pediatric studies evaluating the efficacy of AVAPS in treating nocturnal hypoventilation are confined to case reports. The aim of this study was to compare AVAPS to conventional bilevel positive airway pressure (BPAP) support in improving hypercarbia in a cohort of pediatric patients with nocturnal hypoventilation.

Retrospective review of patient records at an established tertiary pediatric sleep laboratory over a six-year period. Ventilatory and sleep study parameters from AVAPS and conventional BPAP titration studies were compared. AVAPS was used only if hypoventilation was not controlled using conventional BPAP. Inspiratory pressures, tidal volumes and compliance were downloaded on final titrated ventilatory settings. Comparisons were made using paired t-test.

A total of 19 patients (11 males, 8 females; median age 10.5 years, range 1 to 20 years) were identified. Diagnoses included: neuromuscular disease (n=9), obstructive hypoventilation (n=5), parenchymal lung disease (n=4) and congenital central hypoventilation syndrome (n=2). AVAPS demonstrated significant improvement in peak (p=0.009) and mean (p=0.001) TcCO₂ parameters compared to conventional bilevel. Oxygenation on AVAPS showed positive trend but did not reach statistical significance. AVAPS delivered higher tidal volumes (p=0.04) using similar pressures. There was no statistically significant difference in OAHI, respiratory arousal index, sleep efficiency and compliance between AVAPS and conventional BPAP.

AVAPS was an effective alternative to conventional BPAP in improving hypercarbia in our selective cohort of pediatric patients. Prospective, longitudinal studies are needed to evaluate the benefits of AVAPS feature in the pediatric population.

The (mis)perception of sleep: factors influencing the discrepancy between self-reported and objective sleep parameters.

J Clin Sleep

Self-reported perception of sleep often differs from objective sleep study measures, but factors predicting the discrepancy between self-reported and objective sleep parameters are controversial, and a comparison of laboratory vs. ambulatory polysomnography (PSG) is lacking.

We retrospectively analyzed PSG tests conducted between 2012 and 2016. Linear regression was applied to predict the discrepancy between self-reported and objective sleep parameters (total sleep time-TST, sleep efficiency-SE, sleep latency-SL), using age, sex, arousal index, type of sleep disorder, and PSG type (laboratory vs. ambulatory) as regressors.

A total of 303 PSGs were analyzed (49% females, median age 48 years), comprising patients with insomnia (32%), sleep-related breathing disorders (27%), sleep-related movement disorders (15%), hypersomnia/narcolepsy (14%), and parasomnias (12%). Sleep disorder was the best predictor of discrepancy between self-reported and objective TST, and patients with insomnia showed higher discrepancy values compared to all other patient groups (p<0.001), independent of age and PSG type (p>0.05). Contributory effects for higher discrepancy values were found for lower arousal index. Patients with insomnia underestimated both TST (median discrepancy: 46 minutes, p<0.001) and SE (median discrepancy: 11%, p<0.001). No significant predictor for discrepancy of SL was found.

Misperception of sleep duration and efficiency is common in sleep lab patients, but most prominent in insomnia, independent of age, sex or laboratory vs. ambulatory recording setting. This underlines the role of PSG in patients with a clinical diagnosis of insomnia and its use in cognitive behavioral therapy.