Background and objective: Recently, several studies have investigated the prevalence of chronic obstructive pulmonary disease (COPD) at high altitude (>1,500 m). However, much remains to be understood about the correlation between altitude and COPD. We aimed to summarize the prevalence of COPD at high-altitudes and find out if altitude could be a risk factor for COPD. Methods: We searched PubMed/Medline, Cochrane Library, Web of Science, SCOPUS, OVID, Chinese Biomedical Literature Database (CBM) and Embase databases from inception to April 30th, 2019, with no language restriction. We used STATA 14.0 to analyze the extracted data. A random-effect model was used to calculate the combined OR and 95% CI. Heterogeneity was assessed by the I 2 statistic versus P-value. We performed a subgroup analysis to analyze possible sources of heterogeneity. The Egger's test and the Begg's test were used to assess any publication bias. Results: We retrieved 4,574 studies from seven databases and finally included 10 studies (54,578 participants). Males ranged from 18.8% to 49.3% and the population who smoked ranged from 3.3% to 53.3%. The overall prevalence of COPD at high-altitude was 10.0% (95% CI [0.08-0.12], P < 0.001). In a subgroup analysis, based on different regions, the results showed that the prevalence in Asia was higher than that in Europe and America. Seven studies compared the relationship between the prevalence of COPD at high-altitudes and the lowlands. The results showed that altitude was not an independent risk factor for the prevalence of COPD (ORadj = 1.18, 95% CI [0.85-1.62], P = 0.321). There was no publication bias among the studies. Conclusions: Our study found a higher prevalence of COPD at high-altitudes than those from average data. However, altitude was not found to be an independent risk factor for developing COPD (PROSPERO Identifier: CRD42019135012).

Objectives: Exacerbations of chronic obstructive pulmonary disease (COPD) are the third largest cause of emergency hospital admissions in the UK. This systematic literature review explored the relationship between the hospitalization rates and the COPD comorbidities, anxiety, and depression. Methods: The Centre for Research Dissemination's framework for systematic reviews was followed using search terms relating to COPD, anxiety, depression, and hospital admission. Papers identified were assessed for relevance and quality, using a suitable Critical Appraisal Skills Programme tool and Mixed Methods Assessment Tool. Results: Twenty quantitative studies indicated that anxiety and depression led to a statistically significant increase in the likelihood of COPD patients being hospitalized. These comorbidities also led to an increased length of stay and a greater risk of mortality postdischarge. Other significant factors included lower Body-Mass Index, Airflow Obstruction, Dyspnea, and Exercise scores, female gender, lower socioeconomic status, poorer patient perceived quality of life, increased severity of lung function, and less improvement in dyspnea from admission to discharge. It was also highlighted that only 27%-33% of those with depression were being treated for it. Four qualitative studies revealed that patients saw anxiety and depression as a major factor that affected their ability to cope with and self-manage their condition. Implications: Findings from the systematic review have highlighted a need for better recognition and treatment of anxiety and depression amongst individuals with COPD. Ongoing research will develop and test strategies for promoting better management and self-management as a means of reducing hospital admissions.

Objectives: Exacerbations of chronic obstructive pulmonary disease (COPD) are the third largest cause of emergency hospital admissions in the UK. This systematic literature review explored the relationship between the hospitalization rates and the COPD comorbidities, anxiety, and depression. Methods: The Centre for Research Dissemination's framework for systematic reviews was followed using search terms relating to COPD, anxiety, depression, and hospital admission. Papers identified were assessed for relevance and quality, using a suitable Critical Appraisal Skills Programme tool and Mixed Methods Assessment Tool. Results: Twenty quantitative studies indicated that anxiety and depression led to a statistically significant increase in the likelihood of COPD patients being hospitalized. These comorbidities also led to an increased length of stay and a greater risk of mortality postdischarge. Other significant factors included lower Body-Mass Index, Airflow Obstruction, Dyspnea, and Exercise scores, female gender, lower socioeconomic status, poorer patient perceived quality of life, increased severity of lung function, and less improvement in dyspnea from admission to discharge. It was also highlighted that only 27%-33% of those with depression were being treated for it. Four qualitative studies revealed that patients saw anxiety and depression as a major factor that affected their ability to cope with and self-manage their condition. Implications: Findings from the systematic review have highlighted a need for better recognition and treatment of anxiety and depression amongst individuals with COPD. Ongoing research will develop and test strategies for promoting better management and self-management as a means of reducing hospital admissions.