Editorial: Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2023 Guidelines for COPD, Including COVID-19, Climate Change, and Air Pollution

Chronic obstructive pulmonary disease (COPD) is defined by the World Health Organization (WHO) and the 2023 Global Initiative for Chronic Obstructive Lung Disease (GOLD) report as, “a heterogeneous lung condition characterized by chronic respiratory symptoms (dyspnea, cough, expectoration, exacerbations) due to abnormalities of the airway (bronchitis, bronchiolitis) and/or alveoli (emphysema) that cause persistent, often progressive, airflow obstruction” [1].

According to the WHO, in 2019, before the COVID-19 pandemic, COPD was the third leading global cause of death, after ischemic heart disease (IHD) and stroke, resulting in 3.23 million deaths [2]. When evaluated using disability-adjusted life years (DALYs), COPD was the seventh leading cause of poor physical health [2]. Worldwide, in 2019, up to 90% of deaths due to COPD were in patients >70 years of age, mainly in low-income and middle-income countries [2]. Although tobacco smoking was associated with >70% of COPD cases in high-income countries, in low-income and middle-income countries, tobacco smoking was associated with 30–40% of COPD cases, and household and environmental air pollution was a major risk factor [2]. Data from the Global Burden of Disease 2019 project, which included 204 countries and territories, identified that in 2019, there were 212.3 million global COPD cases associated with 74.4 million DALYs and 3.3 million deaths [3]. The most important factors related to the rates of DALYs for COPD included tobacco smoking (46.0%), pollution from ambient particulate matter (20.7%), and occupational exposure to particulate matter, fumes, and gases (15.6%) [3]. In the US, COPD has consistently been ranked as a significant cause of death, with more than 120,000 deaths recorded in 2020, the first year of the COVID-19 pandemic [4].

For many years, COPD was considered rather simplistically to consist of chronic bronchitis and emphysema. However, comorbidities include bronchiectasis, lung cancer, cardiovascular disease, pulmonary hypertension, osteoporosis, metabolic syndrome, and cognitive impairment [5]. There is also a recognized genetic predisposition to COPD [6]. A further misconception about COPD is that it is mainly a disease of cigarette smokers. However, risk factors for COPD also include environmental inhalational exposure [7].

In January 1997, international COPD experts, representatives of the US National Heart, Lung, and Blood Institute (NHLBI), and WHO met in Brussels, Belgium, to develop the Global Initiative for Chronic Obstructive Lung Disease (GOLD) [8]. The meeting participants agreed to establish a panel with expertise on COPD-related topics to prepare evidence-based guidelines on the prevention, diagnosis, and management of COPD [8]. In 2001, the GOLD initiative was launched, with continued collaboration with the NHLBI and WHO [9].

In 2023, Gold published an update on the previous 2017 report and executive summary [1,10]. The GOLD 2023 report includes relevant topics from the clinician’s perspective and evidence published since GOLD 2017 [1,10]. GOLD 2023 proposed the new definition of COPD, which is also adopted by the WHO [1,10]. GOLD 2023 also recognizes that since 2017, there has been a global COVID-19 pandemic due to SARS-CoV-2 [11]. Patients with COPD are not more likely to become infected with SARS-CoV-2, but they have worse outcomes from COVID-19 [11]. Also, climate change has been associated with changes in air quality that have impacted both the complications and incidence of COPD, respectively [12,13].

The 2023 GOLD report now includes recommendations for COPD patients diagnosed with COVID-19 [1,10]. GOLD highlights that COPD patients should follow infection control measures to prevent infection with SARS-CoV-2, including social distancing and hand-washing [14]. GOLD also recommends COVID-19 vaccination according to national guidelines and mask-wearing when there is a high community incidence of COVID-19 [1,10]. Importantly, COVID-19 patients are recommended to comply with their prescribed oral and inhaled respiratory medications for COPD [15]. There is evidence that reductions in exacerbation rates and hospitalization for COPD occurred during the initial phases of the COVID-19 pandemic, possibly due to adherence to infection control measures [14]. GOLD also highlights that COPD patients are not at increased risk of contracting the SARS-CoV-2 virus, which may result from increased adherence to infection control measures [16,17]. However, evidence supports that when potentially confounding variables have been analyzed, COPD patients with COVID-19 have a significantly increased risk of hospitalization, admission to the intensive care unit, and mortality [17]. The 2023 GOLD guidelines also recommend that COPD patients presenting with new or worsening respiratory symptoms that may be due to COVID-19 should be tested for SARS-CoV-2 infection [1,10].

Reduced air quality has an established role in the etiology and progression of COPD [3]. Air pollution can consist of increased ozone levels, particulate matter (PM) <2.5 μm, heavy metals, oxides of nitrogen or sulfur, and other ‘greenhouse gases,’ and is associated with an increased incidence of COPD [1,10]. In low-income and middle-income countries, air pollution is associated with up to 50% of the attributable risk for COPD [1,10]. Environmental and occupational exposure to organic and inorganic dust, fumes, and chemicals are environmental risk factors for COPD that have been under-appreciated [18,19]. In 2002, a study of data from the US Third National Health and Nutrition Examination Survey (NHANES III) estimated that the proportion of cases of COPD attributable to poor air quality in the workplace was almost 20% in smokers and more than 30% in never-smokers [20]. The risk of air pollution is dose-dependent, but with no identifiable safe levels, and even in countries with relatively low air pollution levels, chronic exposure to oxides of nitrogen and sulfur and PM <2.5 μm significantly impairs lung function in children and increases the risk for COPD in adults [21,22]. In patients with COPD, air pollution increases the risk of exacerbations, hospitalizations, and patient mortality [23].

In May 2023, the GOLD Scientific Committee on Air Pollution and COPD confirmed that air pollution increasingly contributes to the pathogenesis of COPD [24]. Recent estimates indicate that, worldwide, up to 50% of the total risk of COPD may now be due to air pollution [24]. The GOLD Scientific Committee identified that gaseous and particulate components of air pollution contribute to COPD and that there are no minimal or safe ambient air pollution levels [24]. Climate change drives heat waves, wildfires, ground-level ozone levels, and gaseous and particulate air pollution [24]. Smoke exposure from wildfires increases acute exacerbations of respiratory illness and hospital admissions, including for COPD [24]. Therefore, GOLD recommends global health policies to reduce ambient air pollution and implement public warning systems to alert patients when ambient air pollution levels exceed minimal thresholds [24].

A recent criticism of GOLD 2023 is the lack of focus on COPD in low-income or resource-poor settings [25]. More information is required regarding long-COVID, or post-acute sequelae of SARS-CoV-2 infection (PASC), in patients with COPD and the long-term effects of severe COVID-19 in patients with COPD who recover from hospitalization [11,26]. The increasing recognition that risk factors for COPD and its etiology are varied and that COPD is not the result of smoking alone has resulted in proposals to classify COPD into etiological subtypes, or ‘etiotypes’ [27].

Conclusions

Clinical guidelines for COPD will continue to evolve, driven by factors that include the effects of climate change on air quality and the long-term effects of respiratory viral infections, including SARS-CoV-2. Future versions of GOLD will likely have evidence-based recommendations that include the long-term effects of air pollution, climate change, and COVID-19 on COPD, etiological subtypes of COPD, and advice for COPD prevention and management in low-income countries.