A pilot study from the investigators group suggests that the prevalence of chronic obstructive pulmonary disease (COPD) among dairy farmers is higher than in the general population. Most characteristics of COPD in dairy farmers (smoking habits, dyspnoea, quality of life, lung function, bronchial exhaled nitric oxide, systemic inflammation, arterial stiffness and exercise capacity) are largely unknown. Although immunization against organic dusts is suspected, the pathophysiology of COPD in dairy farmers is also unknown.

This study therefore aims at (i) comparing the prevalence of COPD in dairy farmers and in subjects without any occupational exposure (control arm) through a vast COPD detection program in the Franche-Comté region; (ii) comparing several characteristics (smoking habits, dyspnoea, quality of life, lung function, bronchial exhaled nitric oxide, systemic inflammation, arterial stiffness and exercise capacity) between dairy farmers with COPD and patients with COPD without any occupational exposure; (iv) identifying etiological factors of COPD in dairy farmers (comparison of exposure and specific immunoglobulin E between dairy farmers with COPD and dairy farmers with normal pulmonary function tests); and (v) constituting a cohort of COPD patients and control subjects for further longitudinal studies.

Data from selected patients (either current or former smokers) with mild COPD and from matched controls will also be analyzed in an ancillary study which objectives are to compare exercise tolerance, ventilatory constraints on tidal volume expansion and dyspnoea between asymptomatic mild COPD subjects, symptomatic mild COPD and healthy controls.

2000 dairy workers and 2000 subjects without any occupational exposure, all aged 40 to 74 years, will take part to a COPD screening program (spirometry and bronchodilation test) between September 2011 and October 2014.

Subjects with COPD and healthy matched controls will attend a second visit. If needed, COPD subjects will be asked to stop any respiratory related medication such as short and long acting bronchodilators 72 hours prior to the visit. All subjects will complete several questionnaires (quality of life, respiratory symptoms, smoking habits,…). A complete medical history will be collected, and a blood sample will be taken. Subjects thereafter will complete arterial stiffness measurement, exhaled nitric oxide and pulmonary function testing pre- and 30-min post-bronchodilator. A symptom-limited incremental cycle exercise test will be performed on the same day, at least 6 hours after the bronchodilator test and at least 4 hours after the meal.

Exposure to organic dusts will be quantified through analyze of electrostatic wipes left at subjects' homes for 10 weeks.

Inclusion Criteria:

• subject aged 40-74 years
• either dairy farmer or unexposed to any occupational risk factor for COPD

Exclusion Criteria:

• COPD in GOLD stage 4
• pregnancy
• treatment with systemic corticosteroids
• established diagnosis of asthma
• established diagnosis of bronchiectasis
• established diagnosis of allergic alveolitis

COPD patients will be defined according to the GOLD criteria (post-bronchodilator FEV1/FVC ratio<70%).

Healthy subjects must have pre-bronchodilator FEV1/FVC ratio >75% and pre-bronchodilator FEV1 >95% of predicted value.