Lung function was assessed with standard determinations
of the forced expiratory volume in 1 second (FEV1)
and forced vital capacity (FVC) with dry rolling-seal
spirometer (Ohio 827 rolling seal spirometer; Ohio Medical
Instrument Company, Cincinnati, Ohio) following the
procedures described by the American Thoracic Society
(ATS) in 1987 [18]. The largest FVC and FEV1 obtained
from acceptable maneuvers were used for the analysis. As
suggested by ATS and European Respiratory Society
(ERS) [19], the predicted values for the lower limit of normal
(LLN) of the FEV1/FVC ratio and FEV1 were calculated
for each subject using gender-, ethnicity-, and agespecific
equations reported by Hankinson et al. (1999)
[20]. In the current analysis, the subject was categorized
as having obstructive lung disorder if his/her observed
FEV1/FVC ratio and FEV1 were less than respective LLN
[20,21].