Patients with COPD, in addition to daytime symptoms, may suffer from nocturnal disturbances. The frequency of nocturnal problems has been reported to be higher in COPD than in the general population and it currently affects up to 50% of patients.

The CASIS questionnaire includes 7 questions and it has been recently validated as an objective tool to evaluate nocturnal symptoms in patients with asthma and COPD. The present study aims to study the validity of the CASIS questionnaire as a predictor of sleep quality measured by objective polysomnographic parameters.

Inclusion criteria:

Patients with written inform consent to participate in the study and all the following criteria will be selected:

• Age 40-80 years
• Smokers or exsmokers of at least 10 pack-years
• Moderate-to-severe COPD

Exclusion criteria:

• Non-stable COPD. Stability is defined as being exacerbation free and without treatment changes for at least 4 weeks prior to baseline evaluation. The presence of a COPD exacerbation previous to the sleep studies (polysomnography, actigraphy, OSLER test) will lead to an early discontinuation of the patient´s participation in the study.
• Heart failure, asthma, cancer or other major medical illness with known effects on sleep quality.
• Unable to understanding the questionnaires administered in the study.
• Known Obstructive Sleep Apnea, other sleep disorder (narcolepsy, periodic limb movements) or shift work.
• Chronic respiratory failure (PaO2 <60 mmHg).
• Treatment with sedatives or antidepressants.

Consecutive patients aged 40-80 years, smokers or exsmokers of at least 10 pack-years, diagnosed with moderate-to-severe COPD (post bronchodilator FEV1% < 70% and FEV1 ≥ 30 but < 80% of predicted in a spirometry performed within 6 months prior to inclusion into the study)