Lung function decline in male heavy smokers relates to baseline airflow obstruction severity.
BACKGROUND
Recent evidence indicates that the rate of lung function decline is steepest in mild COPD and slower in moderate to severe COPD. The current study assessed whether lung function decline relates to baseline airflow obstruction severity in male heavy smokers.


METHODS
In total, 2,003 male smokers with a mean (SD) age of 59.8 (5.3) years underwent pulmonary function testing at baseline and after 3-year follow-up. Participants were classified by entry FEV1/FVC as follows: group 1, >70%; group 2, <70%, but greater than lower limit of normal (LLN); and group 3, less than LLN. Differences in lung function decline among the groups were assessed using multiple regression after adjustment for pack-years, smoking status (current or former smoker), presence or absence of mucus production, medical center, height, age, CT scan-derived emphysema severity (15th percentile), observation time (years in study), and the baseline values.


RESULTS
Over 3 years, the mean (SD) FEV₁/FVC, FEV₁, and maximum expiratory flow at 50% of FVC decreases in group 1 were 3.1% (1), 0.21 L (0.07), and 0.40 L/s (0.26), respectively. In group 3, these decreases were 2.4% (1.1), 0.15 L (0.08), and 0.06 L/s (0.19), respectively. All lung function parameters showed the greatest decline in group 1 (P < .001).


CONCLUSIONS
Diagnosing COPD based on the presence of more severe airflow obstruction (as defined by FEV₁/FVC less than LLN) means that, at the time of such a diagnosis, subjects had passed the phase of strong lung-function decline.


BACKGROUND
ISRCTN Register; No.: ISRCTN63545820; URL: www.trialregister.nl
Division of Heart and Lungs, Department of Respiratory Medicine, University Medical Center Utrecht, Utrecht.
Firdaus A A
FAA
Mohamed Hoesein
Division of Heart and Lungs, Department of Respiratory Medicine, University Medical Center Utrecht, Utrecht. Electronic address: p.zanen@umcutrecht.nl.
Pieter
P
Zanen
Department of Epidemiology, University Medical Center Groningen, University of Groningen, Groningen.
H Marike
HM
Boezen
Department of Pulmonology, University Medical Center Groningen, University of Groningen, Groningen.
Harry J M
HJM
Groen
Image Sciences Institute, Department of Radiology, University Medical Center Utrecht, Utrecht; Diagnostic Image Analysis Group, Department of Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Bram
B
van Ginneken
Department of Radiology, University Medical Center Utrecht, Utrecht.
Pim A
PA
de Jong
Department of Pulmonology, University Medical Center Groningen, University of Groningen, Groningen.
Dirkje S
DS
Postma
Division of Heart and Lungs, Department of Respiratory Medicine, University Medical Center Utrecht, Utrecht.
Jan-Willem J
JJ
Lammers
D000368:Aged; D000402:Airway Obstruction / Q000503:physiopathology*; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008137:Longitudinal Studies; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012129:Respiratory Function Tests; D012720:Severity of Illness Index; D012907:Smoking / Q000009:adverse effects*; D014797:Vital Capacity / Q000502:physiology