All models were adjusted
for sex, age, squared age,weight, current smoking status and packyears
smoked, whereas models for the absolute spirometry
parameters, FEV1 and FVC, were additionally adjusted for
standing height. To test for potential effect modification, final
models were stratified according to the presence of chronic
bronchitis, dyspnea (MRC ,3/$3) and GOLD stages (I–II and
III–IV).