Study objective: Diffusing capacity of the lung for
carbon monoxide (Dlco) is frequently assessed as part of a
thorough pulmonary function assessment in patients with pulmonary or
cardiopulmonary diseases. However, little information regarding the
longitudinal trends of Dlco is available. In this study, we
examined the temporal trends in Dlco to determine the
effects of smoking and changes in smoking habits.
Design: A longitudinal study was recently conducted in the
Po River Delta area of northern Italy, in which Dlco
measurements were taken approximately 8 years apart in the same
subjects; this offered the unique opportunity to assess the temporal
changes in Dlco. The longitudinal Dlco data
were analyzed independently in two age groups (20 to 40 years, and≥
40 years) using a repeated-measures analysis.
Results: Included were 928 subjects > 20 years old who
had Dlco assessments both at baseline and follow-up. Male
subjects had higher mean levels of Dlco than female
subjects in the older age group (≥ 40 years). Continuous smokers had
significantly lower Dlco levels than “never-smokers,”
but their changes in Dlco during follow-up were the same.
This suggests that the lung damage due to smoking had occurred prior to
Dlco testing. We also found that the annual decline in
Dlco accelerated with age in adults ≥ 40 years old.
Conclusions: We conclude that in adults ≥ 40 years of age
from the general population, Dlco accelerates downwards
regardless of gender, smoking, and initial FEV1