During Visit 1, subjects will be given an Electronic Case Report Form (eCRF) with a series of questionnaire such as Health Related Quality of Life (HRQoL) CAT questionnaire, HADS anxiety scale, YPAS physical activity questionnaire, ECSC respiratory symptoms questionnaire, occupational exposure related questionnaire, MMSE questionnaire, Fagerstrom test, Prochaska test.

Subjects in COPD cohort will be classified according to sex and age groups, and the association between prevalence and age will be explored from the chi-squared test and linear-by-linear association. The prevalence of COPD in different age and sex groups will be compared according to the FEV1/FVC ratio.

Presence of comorbidities among subjects with and without COPD will be evaluated using the Charlson and COPD specific comorbidity test (COTE indices), which associate long-term mortality with subject comorbidity.

COPD severity according to GOLD criteria will be evaluated from the results of FEV1/FVC from the post-bronchodilator test. Subjects will be classified into 4 groups namely GOLD 1, GOLD 2, GOLD 3 and GOLD 4 for COPD severity with GOLD 1= mild and GOLD 4 = very severe COPD.

Subjects will be distributed based on GesEPOC into 4 phenotypes that determine differential treatment: non-exacerbator; mixed COPD-asthma; exacerbator with emphysema and exacerbator with chronic bronchitis.

The risk factors of COPD including level of physical activity, degree of smoking, occupational exposure and exposure to smoke from biomass combustion will be analyzed in COPD cohort.

The relationship between the diagnosis of COPD, the level of physical activity and smoking will be assessed first by describing physical activity and smoking based on study cohorts. In the subpopulation of subjects who are smokers, the score on the Fagerstrom Test calculated as the sum of the 6 items (0-10) will be described and it will also be categorized as follows: mild dependency (0-2), medium dependency (3-5) and high dependency (6-10), as well as the smoking cessation phase in which they are, as assessed by Prochaska's stage: pre-contemplation, contemplation, preparation, action, maintenance, termination and relapse.

It will be assessed whether treatment received in the study's COPD population complies with current regulations. The rate of undertreatment and overtreatment in subjects with COPD will also be evaluated. The percentage of COPD subjects who are treated according to the provisions of GesEPOC and according to GOLD will be compared in a post hoc analysis.

The prevalence of smoking and electronic cigarette use in people of 40 years of age or older in Spain and by sex will be described.

The level of nicotine dependence among smokers will be assessed using Fagerstrom test. The test will consist of 6 items and the final score will range from 0- 10 with higher score correlating with higher nicotine dependency. The phase of smoking cessation of subjects will also be assessed using the Prochaska's test. In this test, 3 questions will be asked to each subject. It will identify the smoker's time of addiction to tobacco based on a series of set stages: pre-contemplation, contemplation, preparation, action and maintenance.

The presence and prevalence of specific respiratory symptoms such as chronic cough, dyspnea will be estimated using the European Coal and Steel Community (ECSC) respiratory symptoms questionnaire. The questions will be divided into 6 sections namely cough, expectoration, dyspnea, wheezing and intra-thoracic pressure, asthma attacks and treatments.

HRQoL will be evaluated by using the COPD Assessment Test (CAT) questionnaire. It will consist of a single dimension with 8 items, each with a response scale of 0 (no limitation) to 5 (very limited). The items will assess the degree of severity of cough, presence of mucus, chest pressure, dyspnea, limited domestic activities, social limitations and limited sleep and energy. The overall score will be described in a range of 0-40 points and will distribute subjects into two groups including CAT less than 10 (low impact of COPD) and CAT more than or equal to 10 (medium/high impact of COPD on the subject).

Possible cognitive impairment will be evaluated in subjects 60 years of age or older using mini-mental state examination (MMSE) questionnaire. It is a rapid screening test for dementia and its evolutionary staging. The test consists of 30 items and will explore five cognitive areas: orientation, fixation, concentration and calculation, memory and language. The total score will range from 0 to 30 points. If the score falls between 0-22, the subject will be considered to have a cognitive deficit and those achieving score from 23-30 will be concluded as subjects without a cognitive deficit.

The presence of anxiety and depression among the subjects will be assessed using the Hospital Anxiety and Depression Scale (HADS). The HADS has two components that include scores for anxiety and depression. The response options are Likert-type, ranging from zero to three, giving a scoring range of 0-21 each. Depending on the HADS score, the subjects will be divided into 3 categories HADS 0-7 (absence of clinically relevant anxiety and/or depression), HADS 8-10 (likely to require consideration), HADS 11-21 (presence of anxiety/ depression relevant symptoms).

The percentage of lean mass index will be evaluated and compared between COPD and non-COPD subjects by using bioimpedance. Body composition will be measured based on the electrical properties of biological tissues.

Exercise tolerance between COPD and non-COPD subjects will be evaluated with the help of 6 minute walk test. The distance in meters and the reason for the stop will be measured, along with the initial and final heart rate and initial and final saturation of oxyhemoglobin (SatO2).

The daily physical activity of COPD and non-COPD subjects will be compared using the Yale Physical Activity Survey (YPAS) questionnaire. YPAS will be calculated as the sum of the 5 sub-indices: index of vigorous activity, easy stroll index, moving index, standing index and sitting index. This index will range from 0 to 137 points. The subjects will be categorized into two groups namely YPAS less than 51 (sedentary subjects) and YPAS more than or equal to 51 (not sedentary subjects).

Age will be recorded for descriptive analysis of the sociodemographic characteristics of the subjects participating in this study.

No. of subjects with different education level, gender, marital and smoking status will be recorded for descriptive analysis of the sociodemographic characteristics of the subjects participating in this study.

BMI will be recorded for descriptive analysis of the sociodemographic characteristics of the subjects participating in this study.

No. of instances of underdiagnosis will be described in the subsample of subjects who, despite declaring they had never received a previous diagnosis of COPD, reflect the presence of the disease from the study results. Also, the no. of instances of overdiagnosis will be described among those who claim having a prior diagnosis of COPD but who show this diagnosis to be unconfirmed after the study results. The correlation between the two variables will be analyzed using the Kappa index.

No. of subjects with abnormal BMI, airflow Obstruction, Dyspnea and Exercise capacity (BODE) index ranging from 0-10 points and BMI, degree of dyspnea, pulmonary function and severe exacerbation (BODEX) index ranging from 0- 9 points will be recorded during multidimensional assessment of COPD.

No. of subjects with attenuation of the lung parenchyma and thickness of the wall of the airway will be determined with the help of computed tomography (CT). No. of subjects with other abnormal parameters including the percentage of emphysema, extension areas, thickness of the airway, volume of the chest muscles, diameter of aorta vs. pulmonary artery, air trapping or coronary calcifications, bronchiectasis and fibrosis will also be assessed.

No. of subjects with intensity of dyspnea and other respiratory symptoms, health-related quality of life, exercise tolerance, physical activity and systemic inflammation will be assessed and compared between the COPD and non-COPD subjects depending on the amount of diffusion lung capacity.