Chronic Obstructive Pulmonary Disease (COPD) is a common chronic respiratory disease (1), which represents a serious public health challenge due to its increasing prevalence and related disability and mortality affecting individuals worldwide (2). The China Pulmonary Health (CPH) study, a national survey conducted in 2018 and comprising adults aged > 20 years from 10 provinces, revealed that the overall prevalence in adults aged > 20 and >40 years old was 8.6 and 13.7%, respectively (2). The Global Burden of Diseases Study (GBD), which was conducted in 2017 and included 195 countries, reported 3.2 million deaths due to COPD, classifying COPD as the seventh leading cause of years of life lost (YLLs) (3, 4).

Early detection, diagnosis, and intervention should be the main approaches to the prevention of COPD (5). Global Initiative for Chronic Obstructive Lung Disease (GOLD) Committee recommends that anyone with characteristic symptoms, such as dyspnea, chronic cough, and sputum production or a history of long-term exposure to risk factors, with especial emphasis on individuals aged > 40 years old, should undergo COPD screening (1). GOLD 2022 indicates that a forced expiratory volume in the first second to forced vital capacity (FEV1/FVC) ratio of <0.70 based on post-bronchodilator spirometry confirmed the presence of persistent airflow limitation. In fact, this is the current diagnostic criterion (1). However, screening spirometry in the general population is somewhat controversial. In 2022, the US Preventive Services Task Force (USPSTF) argued that there is still no evidence that screening for COPD in asymptomatic patients positively affects the health-related quality of life (6, 7). Given the lack of experienced spirometry examiners, the confusion related to diagnosis criterion, and the low utilization of bronchodilators before the screening, many spirometry procedures failed to meet the guidelines, resulting in serious underdiagnoses and misdiagnoses of COPD (8, 9). Moreover, false-positive reports due to improper operation might have adverse consequences, such as unreasonable anxiety and/or depression (10).

In order to compare whether the general population, especially those without characteristic symptoms, need spirometry screening, we conducted a screening of residents aged > 40 years old in Minhang District, Shanghai (China) by using a questionnaire and spirometry, which were then analyzed to assess the differences in demographic characteristics, symptoms, lifestyles, and disease comorbidities between non-COPD residents and newly diagnosed mild to moderate COPD patients.

COPD is largely underestimated and underdiagnosed, where newly diagnosed patients mainly appear with mild to moderate disease (16). In the current study, only one-tenth of COPD patients had been previously diagnosed with COPD, and more than three-fourths of newly diagnosed COPD were mild to moderate patients. About half of these mild to moderate patients were asymptomatic, which might be related to the high missed diagnosis rate, since it is difficult to detect mild symptoms, especially when they do not interfere with daily life (17). Asymptomatic COPD is a universal occurrence among patients. For example, among 5,000 people included in the Third National Health and Nutrition Examination Survey in the US, 70% of those with undiagnosed COPD denied having cough or phlegm (18). According to COPD surveillance of Chinese residents in 2014–2015, 66.5% of 9,120 COPD patients had no respiratory symptoms (19).

Our multivariate analysis revealed no significant differences in symptoms and lifestyle factors between newly diagnosed COPD patients and non-COPD participants, which is consistent with some other studies. A study of 678 people in Sousse reported no significant differences in education, family history of COPD, chronic cough and phlegm, dyspnea, and diabetes between newly diagnosed COPD patients and non-COPD participants; however, COPD patients had lower BMI (20). Another study, which included 1,332 participants from the Canadian Cohort of Obstructive Lung Disease (CanCOLD) Study, reported no significant differences in mild-to-moderate cough and phlegm, sex, and numbers of comorbidities (21).

In the present study, older age, male sex, and sleep quality were significantly associated with newly diagnosed COPD, which are the emphasized questions in commonly used COPD screening scales. However, according to screening questionnaire scores, lung function did not significantly differ. Remarkably, symptomatic participants had worse lung function than asymptomatic participants, which indicated that symptoms other than sex and BMI had an important role in lung function. Similarly, a Swiss study, which included the general population, showed that individuals with cough, phlegm, or dyspnea had worse lung function (22).

The WHO definition of screening advocates that screening should be performed for common and treatable diseases with clear natural history. COPD is a widely recognized complex and heterogeneous disease (23). Spirometry is currently considered the gold standard for COPD screening due to its high sensitivity, specificity, and reproducibility (24). Yet, the fixed cut-off of FEV₁/FVC commonly leads to over diagnosis of the elderly because of a faster decline in FEV₁ than in FVC that occurs with age (25). In addition to an acceptable and effective screening method, an economic balance between the cost of identifying a case and acquired benefits is also essential. First, the price of a spirometer is high and cannot be afforded by most primary care clinicians (26). Moreover, it is further aggravated by the cost of post-bronchodilator spirometry and the training of physicians. Considering the huge population base in China, the cost of screening would be overwhelming. Besides, not all mild COPD patients progress to a more severe stage (27) and these people were at increased risks of anxiety and depression (28). A previous study revealed that some patients do not care to assess undiagnosed, especially asymptomatic diseases. GOLD notes no evidence that early spirometry screening of asymptomatic patients effectively improves COPD management or prognosis (7, 29, 30). Also, to date, the only known intervention to alter the natural history of COPD is smoking cessation. Only smoking cessation, oxygen therapy, and lung volume reduction surgery were beneficial in decreasing mortality (10, 31). Moreover, true-positive early diagnoses and false-positive reports can lead to irrational anxiety and depression (10). It is also important to consider potential treatment harms like pneumonia and decreased bone density with LABAs and corticosteroids (32).

The current situation concerning COPD screening is that physicians often pay low attention to respiratory symptoms, while some commonly used COPD screening questionnaires mainly focus on risk factors whilst ignoring symptoms (12, 14). Accordingly, the purpose of COPD screening should be seriously revised, including taking sex into account (33), it should be used to help undiagnosed patients with respiratory symptoms obtain early diagnosis rather than extensively screen the general population (34). Mild airflow restriction is not easily detected, especially by those individuals whose lifestyle does not include exercise. In addition, some patients attribute the symptoms as a normal consequence of old age or smoking, i.e., most patients who state being asymptomatic are actually symptomatic; however, they fail to recognize the symptoms (20). Therefore, physicians should pay more attention to respiratory symptoms and avoid the “don't ask, don't tell” strategies (34).

This is a large-scale study based on a community population. All participants were screened by trained physicians and post-bronchodilator spirometry, which strictly complied with the 2014 guidelines for pulmonary function examination. The study also has some limitations. Using fixed FEV₁/FVC as a diagnostic criterion may result in over diagnosis of the elderly (35). Besides, the questionnaire was designed mainly for COPD screening. Therefore, only a few comorbidities were included and did not include hypertension which is a common chronic disease. And the comorbidities were self-reported. Therefore, it would underestimate the prevalence of comorbidities in COPD patients (36, 37). Additionally, the cross-sectional study cannot assess long-term outcomes due to its nature.

Newly diagnosed COPD patients in a community-based setting showed few differences from the general population, suggesting a targeted case finding strategy could be more beneficial than general screening. In addition, more attention should be paid to respiratory symptoms, developing more symptom-based screening tools, and exploring new therapies and interventions for COPD in the early stage.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by the Ethics Committee of Shanghai Fifth people's Hospital (2018 Ethics Approval No. 130). The patients/participants provided their written informed consent to participate in this study. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.

Conceptualization: JS and NW. Formal analysis: XY and NW. Investigation: ZZ, YD, JL, SY, QX, and SH. Supervision: YZ, HD, JX, ZJ, and QJ. Writing—original draft: XY and ZZ. Writing—review and editing: XY, ZZ, JS, and NW. All authors have read and agreed to the published version of the manuscript.