Asthma as a risk factor for COPD in a longitudinal study.
BACKGROUND
For several years, asthma and COPD have been regarded as distinct entities, with distinct clinical courses. However, despite distinctive physiologic features at the time of diagnosis, and different risk factors, the two diseases over time may develop features that are quite similar.


OBJECTIVE
To evaluate the association between physician-diagnosed asthma and the subsequent development of COPD in a cohort of 3,099 adult subjects from Tucson, AZ.


METHODS
A prospective observational study. Participants completed up to 12 standard respiratory questionnaires and 11 spirometry lung function measurements over a period of 20 years. Survival curves (with time to development of COPD as the dependent variable) were compared between subjects with asthma and subjects without asthma at the initial survey.


RESULTS
Subjects with active asthma (n = 192) had significantly higher hazard ratios than inactive (n = 156) or nonasthmatic subjects (n = 2751) for acquiring COPD. As compared with nonasthmatics, active asthmatics had a 10-times-higher risk for acquiring symptoms of chronic bronchitis (95% confidence interval [CI], 4.94 to 20.25), 17-times-higher risk of receiving a diagnosis of emphysema (95% CI, 8.31 to 34.83), and 12.5-times-higher risk of fulfilling COPD criteria (95% CI, 6.84 to 22.84), even after adjusting for smoking history and other potential confounders.


CONCLUSIONS
Physician-diagnosed asthma is significantly associated with an increased risk for CB, emphysema, and COPD.
Silva
Graciela E
GE
Arizona Respiratory Center, University of Arizona, College of Medicine, Tucson, 85724, USA.
Sherrill
Duane L
DL
Guerra
Stefano
S
Barbee
Robert A
RA
D000328:Adult; D001249:Asthma / Q000150:complications*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D029424:Pulmonary Disease, Chronic Obstructive / Q000209:etiology*; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects; D013147:Spirometry; D011795:Surveys and Questionnaires