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 organ systems and asked (yes/no questions) whether the
participant ‘suffered or had suffered from any disease of
that system, providing examples of the most common
conditions for each system. It also included questions on
smoking habits and medical treatments. The questionnaire
was used to support the subsequent clinical interview.