Sleep in Chronic Obstructive Pulmonary Disease: Evidence Gaps and Challenges

Association of lifestyle components with prevalence of chronic obstructive pulmonary disease (COPD): Findings of a cohort study

BACKGROUND

Chronic Obstructive Pulmonary Disease (COPD) is a complex condition influenced by various lifestyle factors. Dietary patterns, physical activity, and sleep quality play a crucial role in the prevalence and management of COPD.

OBJECTIVES

We aimed to evaluate the relationship between dietary patterns, physical activity, and sleep quality with the prevalence of COPD in the PERSIAN Organizational Cohort study at Mashhad University of Medical Sciences (POCM).

METHODS

This cohort study utilized data from 12,000 participants in POCM. Dietary intake was assessed using a food frequency questionnaire, physical activity was measured using the International Physical Activity Questionnaire, and sleep quality was evaluated using the Pittsburgh Sleep Quality Index. Spirometry was performed to diagnose and categorize COPD severity.

RESULTS

Out of the eligible 4269 participants, 3768 (91 %) were healthy and 373 (9 %) had COPD. Compared to the highest quartile, the second quartiles and third quartiles of the healthy dietary pattern were inversely associated with COPD prevalence, even after adjusting for confounders for the second and third quarters respectively. The second quartile of the fast-food dietary pattern was positively associated with COPD. Older age and poorer sleep quality were also significantly associated with higher COPD prevalence. Physical activity levels did not differ between healthy and COPD individuals.

CONCLUSIONS

Findings of this study indicate that healthy diet with more fruits, vegetables, and whole grains was related to reduced incidence of COPD, while the incidence of COPD was related to poor sleep quality. These findings highlight the possible interplay of lifestyle factors and respiratory health.

Prevalence of obstructive sleep apnea in patients with chronic obstructive pulmonary disease in Vietnam

PURPOSE

Chronic obstructive pulmonary disease and obstructive sleep apnea are two common respiratory diseases. Chronic obstructive pulmonary disease patients co-morbid with obstructive sleep apnea are associated with increased cardiovascular adverse events, frequent acute exacerbations, and higher mortality. Only a few studies on obstructive sleep apnea among patients with chronic obstructive pulmonary disease are available in Vietnam. The study aims to determine the prevalence of obstructive sleep apnea in patients with chronic obstructive pulmonary disease in Vietnam.

METHODS

This is a cross-sectional study in patients with chronic obstructive pulmonary disease at multi-sites in Vietnam: the People's Hospital of Gia Dinh, Bach Mai Hospital, Phoi Viet Clinics, and Lam Dong Medical College using type 3 sleep monitoring device at sleep labs to diagnose obstructive sleep apnea in all study participants.

RESULTS

Two hundred seventy-eight patients with chronic obstructive pulmonary disease were enrolled. Among the patients, 93.2% were male, with an average age of 66.9 ± 9.3 and a BMI of 21.9 ± 3.8 kg/m2; 82.0% were symptomatic including 44.6% in group B and 37.4% in group D with average post-FEV1 of 49.8 ± 18.3% predicted values. One hundred seventeen patients (42.1%) with chronic obstructive pulmonary disease presented obstructive sleep apnea defined by AHI ≥ 15 events/h.

CONCLUSIONS

The prevalence of obstructive sleep apnea in patients with chronic obstructive pulmonary disease in Vietnam was 42.1% for an AHI of ≥ 15 events/h.

Identification of sleep phenotypes in COPD using machine learning-based cluster analysis

BACKGROUND

Disturbed sleep in patients with COPD impact quality of life and predict adverse outcomes.

RESEARCH QUESTION

To identify distinct phenotypic clusters of patients with COPD using objective sleep parameters and evaluate the associations between clusters and all-cause mortality to inform risk stratification.

STUDY DESIGN AND METHODS

A longitudinal observational cohort study using nationwide Veterans Health Administration data of patients with COPD investigated for sleep disorders. Sleep parameters were extracted from polysomnography physician interpretation using a validated natural language processing algorithm. We performed cluster analysis using an unsupervised machine learning algorithm (K-means) and examined the association between clusters and mortality using Cox regression analysis, adjusted for potential confounders, and visualized with Kaplan-Meier estimates.

RESULTS

Among 9992 patients with COPD and a clinically indicated baseline polysomnogram, we identified five distinct clusters based on age, comorbidity burden and sleep parameters. Overall mortality increased from 9.4 % to 42 % and short-term mortality (<5.3 years) ranged from 3.4 % to 24.3 % in Cluster 1 to 5. In Cluster 1 younger age, in 5 high comorbidity burden and in the other three clusters, total sleep time and sleep efficiency had significant associations with mortality.

INTERPRETATION

We identified five distinct clinical clusters and highlighted the significant association between total sleep time and sleep efficiency on mortality. The identified clusters highlight the importance of objective sleep parameters in determining mortality risk and phenotypic characterization in this population.

Symptom Cluster Profiles in Adults with Chronic Obstructive Pulmonary Disease and Insomnia

BACKGROUND

People with chronic obstructive pulmonary disease (COPD) and insomnia may experience multiple symptoms that can affect physical function, but little research has focused on symptom clusters in this population.

OBJECTIVES

This study aimed to identify subgroups of people with COPD and insomnia based on a pre-specified symptom cluster and determine whether physical function differed in the subgroups.

METHODS

This secondary data analysis included 102 people with insomnia and COPD. Latent profile analysis classified subgroups of individuals sharing similar patterns of five symptoms: insomnia, dyspnea, fatigue, anxiety, and depression. Multinomial logistic regression and multiple regression determined factors associated with the subgroups and whether physical function differed among them.

RESULTS

Three groups of participants were identified based on the severity of all five symptoms: low (Class 1), intermediate (Class 2), and high (Class 3). Compared to Class 1, Class 3 showed lower self-efficacy for sleep and for COPD management and more dysfunctional beliefs and attitudes about sleep. Class 3 showed more dysfunctional beliefs and attitudes about sleep than Class 2. Class 1 showed significantly better physical function than Classes 2 and 3.

CONCLUSIONS

Self-efficacy for sleep and for COPD management and dysfunctional beliefs and attitudes about sleep were associated with class membership. As physical function differed among subgroups, interventions to improve self-efficacy for sleep and for COPD management and minimize dysfunctional beliefs and attitudes about sleep may reduce symptom cluster severity, in turn enhancing physical function.

Differences of Clinical Characteristics and Drug Prescriptions between Men and Women with COPD in China

BACKGROUND

Sex differences in symptoms exist in patients with COPD. Our aim is to measure the differences between men and women with COPD, focusing on risk factors, symptoms, quality of life and drug prescriptions.

METHODS

In this cross-sectional observational study, patients with COPD were collected in China; demographic characteristics, smoking history, occupational exposure, biomass exposure, lung function, dyspnea, quality of life, and prescriptions for inhaled medications were collected. The nearest neighbor algorithm was used to match female and male patients (ratio 2:1) on age, body mass index, and lung function.

RESULTS

Compared with 1462 men, the 731 women generally had lower educational levels and were married less (both p < 0.001). A total of 576 (90.0%) women did not smoke cigarettes. More men were exposed to occupational dust (539 (36.9%) vs. 84 (11.5%), p = 0.013), while more women were exposed to biomass smoke (330 (45.1%) vs. 392 (26.8%), p = 0.004). Except for phlegm and chest tightness, women had more complaints than men for cough, breathlessness, activities, confidence, sleep and energy (p < 0.05). In addition, more women were prescribed triple therapy than men (236 (36.3%) vs. 388 (31.0%), p = 0.020).

CONCLUSIONS

There are obvious discrepancies in the quality of life and use of inhaled medications between male and female patients with COPD.

Comparison of the Associations between Self-Reported Sleep Quality and Sleep Duration Concerning the Risk of Depression: A Nationwide Population-Based Study in Indonesia

There is substantial evidence that a lack of sleep quality and duration can increase the risk of depression in adults. Still, few studies have compared sleep quality and duration to the risk of depression in Indonesia. Therefore, this study aimed to compare the prevalence and risk of depression associated with both sleep quality and duration and identified those factors associated with sleep quality with sleep duration. This study was a cross-sectional study, and the data were obtained from the 2014 Indonesian Family Life Survey, with a total sample comprised of 19,675 respondents aged older than 15 years old. A self-reported questionnaire was used to assess sleep quality and duration. Depression was assessed using the Center for Epidemiologic Studies Depression (CESD-10) questionnaire. Logistic regression was used to examine the risk of depression, and multinomial logistic regression was used to examine the risk of poor sleep quality with consideration to sleep duration. The prevalence of depression was the highest in the poor sleep quality and long sleep duration groups (48.5%). After all variables associated with depression were adjusted, poor sleep quality was identified as a factor leading to a higher risk of depression (OR = 4.2; 95% CI: 3.7-4.6; p < 0.001) than long sleep duration (OR = 1.4; 95% CI: 1.2-1.6; p < 0.001). Furthermore, the interaction between poor sleep quality and long sleep duration gave the highest risk of depression (OR = 4.4; 95% CI: 3.6-5.3); p < 0.001). Multinomial logistic regression revealed that the factors leading to a significant increase in the risk of poor sleep quality, with consideration to sleep duration, in the population were age, gender, marital status, education, wealth index, physical activity, chronic illness, season, and urban area (p < 0.05). Sleep quality was found to be associated with a higher risk of depression than sleep duration. The findings of this study may be beneficial to healthcare professionals who develop health promotion strategies for reducing the incidence of depression in communities.

Evaluation of dyspnea severity and sleep quality in patients with novel coronavirus

AIM

Dyspnea, a common symptom of novel coronavirus, can negatively affect sleep quality. The aim of this study was to evaluate the relationship between dyspnea severity and sleep quality in patients with COVID-19.

STUDY DESIGN

A cross-sectional design was used.

METHODS

Using the researcher's mobile phone, data were collected via an online questionnaire from patients (n = 100) who agreed to participate in the study. The data-collection form comprised three parts: a patient descriptive information form, the Dyspnea-12 Questionnaire, and the Richards-Campbell Sleep Questionnaire (RCSQ).

RESULTS

The mean age of patients was 46.39 ± 12.61 years and 66.0% were men. Patients who were treated in the intensive care unit had bachelor's degree or more and patients with comorbid diseases had low mean scores from the RCSQ and high mean scores from the Dyspnea-12 Questionnaire (P < .001, P < .001; P = .047, P < .001; P < .001, P < .001, respectively). Patients who were not receiving oxygen therapy had higher RCSQ mean scores and lower Dyspnea-12 Questionnaire scores (P < .001, P < .001; P < .001, P < .001, respectively). There was a strong negative relationship between the total scores obtained from the RCSQ and the Dyspnea-12 Questionnaire (r = -.701, P < .001).

CONCLUSIONS

Sleep quality is affected by dyspnea severity in patients with COVID-19. Sleep quality and dyspnea severity are also influenced by quite different factors, and these should be addressed and eliminated by nurses as part of a holistic approach. The results of this study will help nurses, especially those providing treatment and care for patients with COVID-19, to identify the factors affecting dyspnea and sleep quality and to plan, implement and evaluate nursing interventions that will reduce their workload.

Association between comorbid sleep apnoea-hypopnoea syndrome and prognosis of intensive care patients: a retrospective cohort study

OBJECTIVE

In this study, we investigated the association between comorbid sleep apnoea-hypopnoea syndrome (SAHS) and the prognosis of patients in an intensive care unit (ICU) to determine whether this relationship varies between different disease subgroups.

METHODS

We conducted a retrospective cohort study using publicly available information from the critical care database Medical Information Mart for Intensive Care III. Adults (≥18 years of age) who attended the ICU for the first time were enrolled. Demographic information and clinical data were obtained from each patient. The primary outcome was 30-day mortality after ICU admission, and the secondary outcomes were in-hospital and ICU mortality. Multivariate logistic regression and Cox regression analyses were used to examine the associations between SAHS comorbidities and the research outcomes. Propensity score matching was used to adjust for potential confounding variables.

RESULTS

Of the 32 989 patients enrolled, 1918 (5.81%) were diagnosed with SAHS as a comorbid condition. Patients with SAHS had a significantly lower 30-day mortality rate compared with those without SAHS (5.27% vs 13.65%, respectively; p<0.001). The frequency of chronic obstructive pulmonary disease, cerebral disease, cardiovascular disease, hypertension, diabetes mellitus and renal failure was significantly different between the two groups. Patients with SAHS demonstrated significantly longer survival compared with patients without SAHS. Multivariate Cox proportional hazards regression identified a significant relationship between SAHS and mortality within 30 days (adjusted HR=0.610, 95% CI 0.499 to 0.747, p<0.0001).

CONCLUSION

SAHS as a comorbid condition decreases the risk of 30-day mortality, in-hospital mortality and ICU mortality among ICU patients.

Sleep Quality Associated with Habitual Physical Activity Level and Autonomic Nervous System of Smokers

BACKGROUND

Few studies have examined the relationship of one's habitual physical activity level and autonomic nervous system (ANS) modulation on sleep quality in smokers.

OBJECTIVE

The aim of this study was to identify changes in the sleep quality of smokers and its relation with their habitual physical activity level and ANS modulation.

METHODS

Forty-two smokers were divided into two groups according to the 50th percentile of the moderate-to-vigorous physical activity (MVPA). Sleep quality was assessed using the Mini-sleep Questionnaire, and ANS modulation was assessed by indices of heart rate variability (HRV). To examine the possible mean differences, the analysis of covariance (ANCOVA) was used, adjusted for age, sex, body composition, pack-years, beta-blockers, anxiety, and depression in log base 10, not including qualitative data, such as sex and beta-blockers. Correlations were made by using the Spearman rank correlation. The statistical significance was set at 5.

RESULTS

The smokers who were less active showed poor sleep quality (p=0.048) and insomnia (p=0.045). Furthermore, the less active group presented decreased parasympathetic modulation [HF (un; p=0.049); RMSSD (ms; p=0.047) and SD1 (ms; p=0.047)] and an increased LF (un) index (p=0.033) and LF/HF ratio (p=0.040). A positive correlation between the total Mini-sleep score with LF (un) index (r=0.317, p=0.041) and LF/HF ratio (r=0.318, p=0.040) and negative correlation with HF (un) index (r= -0.322, p=0.038).

CONCLUSIONS

Smokers with lower levels of habitual physical activity showed poor sleep quality and alterations in autonomic nervous system modulation; (Arq Bras Cardiol. 2020; [online].ahead print, PP.0-0).

The deleterious effects of chronic obstructive pulmonary disease and obstructive sleep apnea: pathophysiology and implications on treatment

Background

Chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA) are both common in the adult population. The coexistence and association of both COPD and OSA have been described as the overlap syndrome. The scope of the present review is to address the magnitude, pathophysiology, clinical presentations, and the deleterious consequences of the coexistence of COPD and OSA in the same patient as well as the current management and treatment options of this association.

Main body of abstract

Epidemiological studies showed a prevalence of the overlap syndrome of up to 1% of the adult population. However, various studies agreed that this association is due to the fact that both COPD and OSA are common rather than an interaction of pathophysiology between the two affections. Nevertheless, sleep may cause adverse effects on breathing and lung functions. While these effects can be neglected in otherwise healthy individuals, they can lead in contrast to disastrous clinical outcomes particularly in vulnerable patients with the overlap syndrome leading to increased risk of cardiovascular diseases, acute COPD exacerbations, increased rates of hospitalizations, and nocturnal deaths. Current guidelines recommend polysomnography (PSG) as the gold standard investigation to diagnose sleep disorders and overlap syndrome. Treatment may include pulmonary rehabilitation, supplemental oxygen therapy, and non-invasive ventilation. Currently, continuous positive airway pressure (CPAP) therapy is the treatment of choice for the overlap syndrome. CPAP effects include improved respiratory mechanics; sleep quality, exercise tolerance, and prolonged survival.

Conclusion

Both COPD and OSA are common in the general population and present a significant risk of increased morbidity and mortality when they coexist in the same patient. Clinicians must carefully evaluate the clinical outcomes and the high risk of cardiovascular complications related to the overlap syndrome. Current data indicate that CPAP treatment leads to amelioration of the health-related quality of life and improve survival in patients with the overlap syndrome.

Physical Activity in Overlap Syndrome of COPD and Obstructive Sleep Apnea: Relationship With Markers of Systemic Inflammation

STUDY OBJECTIVES

Low physical activity (PA) is associated with poor health outcomes in chronic obstructive pulmonary disease (COPD). Overlap syndrome (OVS), the co-occurrence of COPD and obstructive sleep apnea (OSA), is highly prevalent. Little is known about PA in OVS, and its relationship with markers of systemic inflammation.

METHODS

We studied 256 persons with stable COPD, 61 (24%) of whom had OVS, who were well characterized in two previous PA studies. PA was directly assessed with the Omron HJ-720ITC pedometer. C-reactive protein (CRP) and interleukin-6 (IL-6) were assayed from peripheral blood. Linear regression models, adjusting for age and forced expiratory volume in 1 second (FEV1) % predicted, assessed daily step counts and CRP and IL-6 levels in OVS, compared to COPD alone. Linear regression models, adjusting for age, FEV1 % predicted, and coronary artery disease, assessed the relationships between PA and CRP and IL-6 in those with OVS versus those with COPD alone.

RESULTS

Compared to COPD alone, persons with OVS walked 672 fewer steps per day (95% CI -1,317 to -28, P = .041). Those with OVS had significantly higher levels of CRP and IL-6 compared to COPD alone. In OVS, each 1,000 fewer steps walked was associated with a 0.875 ng/mL (95% CI 0.767 to 0.997) increase in IL-6, independent of lung function.

CONCLUSIONS

Persons with OVS have significantly lower levels of PA and higher levels of inflammatory biomarkers, compared to COPD alone. Lower PA is significantly associated with higher IL-6 levels in OVS.

Research Priorities in Pathophysiology for Sleep-disordered Breathing in Patients with Chronic Obstructive Pulmonary Disease. An Official American Thoracic Society Research Statement

BACKGROUND

Obstructive sleep apnea (OSA) and chronic obstructive pulmonary disease (COPD) are common conditions; the co-occurrence of these diseases, called the overlap syndrome (OVS), has been associated with poor health outcomes.

PURPOSE

The purpose of this Official American Thoracic Society Research Statement is to describe pathophysiology, epidemiology, outcomes, diagnostic metrics, and treatment of OVS, as well as to identify important gaps in knowledge and make recommendations for future research.

METHODS

Clinicians and researchers with expertise in sleep medicine, pulmonary medicine, or both were invited to participate. Topics were divided among the participants according to their interest and expertise. A literature search was conducted; the search was not a formal systematic review. Evidence was considered and supplemented with the panelists' nonsystematic clinical observations. Important knowledge gaps were identified.

RESULTS

Recommendations for research to fill existing knowledge gaps were made. The recommendations were formulated by discussion and consensus.

CONCLUSIONS

Many important questions about OVS exist. This American Thoracic Society Research Statement highlights the types of research that leading clinicians and researchers believe will have the greatest impact on better understanding the spectrum of disease, improving diagnosis, and optimizing therapy.

Sleep Disorders and Adherence to Inhalation Therapy in Patients with Chronic Obstructive Pulmonary Disease

Sleep disorders are common in patients with chronic obstructive pulmonary disease (COPD) and are associated with greater disease severity, more frequent exacerbations, greater use of emergency health care, and higher mortality. They may contribute to worsening of COPD course by reducing patients' adherence to treatment. The aim of this study was to evaluate quality of sleep in COPD patients and to assess the relationship between impaired sleep and adherence to inhalation therapy. The study included 106 COPD patients who were asked to answer the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and Adherence to Refills and Medications Scale (ARMS). Clinical and demographic data were also collected. We found that over 60% of patients presented with sleep disorders (PSQI ≥5) and 75% with daytime sleepiness. None of the patients presented with optimal adherence to pharmacotherapy. Worse adherence was correlated with greater sleep disorders (r = 0.56; p < 0.001). ARMS questionnaire proved to be of high overall internal consistency (Cronbach's alpha = 0.85). In conclusion, poor quality of sleep coexists with poor adherence to treatment among COPD patients. ARMS was proved to be a reliable tool for the assessment of adherence. Interventions aimed at improving sleep quality may be helpful to improve adherence to inhalation therapy in COPD patients.

COPD Guidelines: A Review of the 2018 GOLD Report

Global Strategy for the Diagnosis, Management, and Prevention of COPD 2018 is a consensus report published periodically since 2001 by an international panel of health professionals from respiratory medicine, socioeconomics, public health, and education comprising the Global Initiative for Chronic Obstructive Lung Disease (GOLD). The GOLD documents endeavor to incorporate latest evidence and expert consensus and are intended for use as "strategy documents" for implementation of effective care for chronic obstructive lung disease (COPD) on a global level. The GOLD 2018 report defines COPD as a "common, preventable and treatable disease that is characterized by persistent respiratory symptoms and airflow limitation that is due to airway and/or alveolar abnormalities, usually caused by significant exposure to noxious particles or gases," with the criteria of "persistent respiratory symptoms" being a new and controversial inclusion since 2017. With the availability of newer pharmacotherapy options, treatment recommendations are made on the basis of a review of the latest literature and directed by symptom burden and health care utilization. Apart from the change in definition, a major shift in the recommendations is the exclusion of severity of airflow limitation as one of the major factors in guiding therapy. We review the salient features of the GOLD 2018 document and provide commentary on features that merit further discussion based on our clinical experience and practice as well as literature review current as of February 2018.

Predictors of Sleep Apnea in the Canadian Population

Older age, obesity, hypertension, snoring, and excessive daytime sleepiness have been associated with sleep apnea. The objective of this study was to determine the prevalence (crude and adjusted), as well as the risk factors, of sleep apnea in the adult Canadian population. Data from the 2009 Sleep Apnea Rapid Response (SARR) questionnaire were used to identify the risk factors, and all sleep-related questions in the SARR questionnaire were used. The outcome variable of interest was health professional-diagnosed sleep apnea. Covariates of interest were demographic variables, population characteristics, respiratory and cardiovascular diseases, and enabling resources. The multiple logistic regression model adjusted for the clustering effect was used to analyze the data. Sleep apnea was diagnosed in 858,913 adults (3.4% of the population), and more men (65.4%) than women (34.6%) were diagnosed with sleep apnea. Multivariable logistic regression analysis indicated that age (45 and older), loud snoring, sudden awakening with gasping/choking (rare/sometimes and once or more a week), and nodding off/falling asleep in driving in the past 12 months were significantly associated with diagnosed sleep apnea. Predictive probability demonstrated that in overweight and obese persons, ≥15 minutes of daily exercise significantly decreased the risk of diagnosed sleep apnea. The conclusion of this study is that in the Canadian population, sleep apnea is associated with older age, loud snoring, and sleeping problems. The protective effect of exercise warrants further investigation.

Long-term Recording of Night-Time Respiratory Symptoms in Patients with Stable COPD II-IV

INTRODUCTION

Night-time respiratory symptoms have a considerable impact on sleep and life quality in patients with chronic obstructive pulmonary disease (COPD). Lack of awareness of night-time symptoms can lead to worsened COPD control. Automated long-term monitoring of respiratory symptoms with LEOSound enables assessment of nocturnal wheezing and cough.

METHODS

In this observational study we investigated the prevalence and severity of cough and wheezing in patients with stable COPD [Global Initiative for Chronic Obstructive Lung Disease (GOLD) II-IV] disease for two consecutive nights with the LEOSound system. 48 patients (30 males, 63%) were eligible for inclusion, median age was 67 years, and body mass index (BMI) was 25.3 kg/m².

RESULTS

In 15 out of 48 patients (31%), we found wheezing periods for at least 10-minute duration. Wheezing periods >30 minutes were monitored in seven patients and wheezing periods >60 minutes were monitored in three patients. The maximum duration of wheezing was 470 minutes in one patient with COPD II. The median wheezing rate differed between the COPD stages and between active and non-active smokers. Cough was found in 42 patients (87.5%) with a range of 1-326 events. The cough-period-index in night one was 0.83 n/hour (P25:0.33||P75: 2.04) and night two 0.97 n/hour (P25:0.25||P75: 1.9). Most of the cough events were non-productive with a median of 0.86.

CONCLUSIONS

Night-time symptoms are common in COPD patients. LEOSound offers an opportunity to evaluate objectively night-time symptoms like wheezing and cough in patients with COPD which remain otherwise unnoticed. We found a high incidence of night-time wheezing in these patients, which was related to persistant smoking.

Long-Term Oxygen Therapy in COPD Patients Who Do Not Meet the Actual Recommendations

Chronic respiratory failure due to chronic obstructive pulmonary disease (COPD) is an increasing problem worldwide. Many patients with severe COPD develop hypoxemic respiratory failure during the natural progression of disease. Long-term oxygen therapy (LTOT) is a well-established supportive treatment for COPD and has been shown to improve survival in patients who develop chronic hypoxemic respiratory failure. The degree of hypoxemia is severe when partial pressure of oxygen in arterial blood (PaO₂) is ≤55 mmHg and moderate if PaO₂ is between 56 and 69 mmHg. Although current guidelines consider LTOT only in patients with severe resting hypoxemia, many COPD patients with moderate to severe disease experience moderate hypoxemia at rest or during special circumstances, such as while sleeping or exercising. The efficacy of LTOT in these patients who do not meet the actual recommendations is still a matter of debate, and extensive research is still ongoing to understand the possible benefits of LTOT for survival and/or functional outcomes such as the sensation of dyspnea, exacerbation frequency, hospitalizations, exercise capacity, and quality of life. Despite its frequent use, the administration of "palliative" oxygen does not seem to improve dyspnea except for delivery with high-flow humidified oxygen. This narrative review will focus on current evidence for the effects of LTOT in the presence of moderate hypoxemia at rest, during sleep, or during exercise in COPD.