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COPD is a progressive disease causing inexorable decline in lung function, right? We were all taught it, but maybe no one checked first. Vestbo et al's ECLIPSE, a simple but large and elegant observational study that continues to furnish new insights into COPD, shows the truth is far more nuanced and complicated.
After following 2,163 patients with COPD of varying severity for 3 years, a complex tapestry of patients emerged. The mean rate of decline in FEV1 was 33 mL/year -- not far off from the 20 to 30 mL/year loss observed in healthy nonsmokers in one major study. But people with COPD varied widely in their rates of FEV1 decline: the standard deviation between individuals was 59 mL -- almost twice the mean (that's big). Other interesting points included:
- Only 38% had a decline of more than 40 mL/year over the 3 years.
- Fewer than half exceeded a loss of 30 mL/year (the upper limit of physiologic decline).
- Fully 8% had an increase in FEV1 of more than 20 mL/year.
- The worse the COPD stage (FEV1), the slower the rate of decline, suggesting COPD may "burn out" over time (authors' words). Conversely, those with milder COPD had faster FEV1 loss.
- Cumulative smoking (pack-years) had no effect on rate of FEV1 decline.
- Current smoking did markedly accelerate FEV1 decline, by an additional 21 mL/year.
- Exacerbations were only weakly associated with accelerated decline of FEV1, by 2 mL/year per exacerbation experienced during the study.
- Emphysema on CT was associated with an increased FEV1 decline of 13 mL/year. Interestingly, a bronchodilator response on spirometry predicted an accelerated FEV1 decline of 17 mL/year.
Treatment may have slowed the rate of FEV1 decline in some patients (making this even more complicated): patients were on standard care throughout, and medications such as inhaled corticosteroids/long-acting beta agonists slow decline in lung function.
Vestbo J et al (ECLIPSE investigators). Changes in Forced Expiratory Volume in 1 Second over Time in COPD. N Engl J Med 2011; 365:1184-1192.