Measurements
Participants were invited to our Outpatient Clinic for
Occupational and Environmental Health for a health
check including a general clinical examination, 12-channel
resting-ECG, lung function testing (spirometry and body
plethysmography), as well as spiroergometry as described
elsewhere [14]. All participants signed a written informed
consent document after the examining physician had explained
the health check-up and the study. Before undergoing
the clinical interview and clinical examinations, the
participants were asked to answer a questionnaire regarding
current and past health problems and to self-assess
their HRQoL. The health problems questionnaire listed