Patients: 50 adult (>35 years) COPD patients GOLD stage I (symptomatic) - IV of the disease, aged > 35 years, non-institutionalized and residing in the canton of Valais. Patients will be recruited by primary care and pulmonary care physicians practicing in the French-speaking part of the canton of Valais. The control group of patients will be constituted of age and gender-matched COPD patients already included in the Swiss COPD cohort study.