 Only a limited percentage
of a population satisfies all criteria of ‘pulmonary
health’,
leaving only a small reference group. The populations of Vlaardingen
and Vlagtwedde (the Netherlands), who took part in a longitudinal
epidemiological study of lung health carried out by the TNO
Working group Epidemiology of CNSLD may serve as an example.
Among adult men investigated by staff of the Physiology Department
of Leiden University fewer than 13% of men and than 48% of
women were lifelong non-smokers. |
 Among women, 70% had never experienced chronic
respiratory symptoms, in men the corresponding percentage was 65%. |
 Applying both criteria, about 1 in 10 males
were assigned to the reference group on the basis of respiratory
symptoms and smoking habits; in women only one third fulfilled
the combined set of criteria. |