Annual change in FEV₁ in elderly 10-year survivors with established chronic obstructive pulmonary disease

Long-term decline in lung function is generally considered to be progressive in individuals with established chronic obstructive pulmonary disease (COPD), despite the presence of intersubject variation. We hypothesized that the annualized rate of decline in forced expiratory volume in 1 second (FEV₁) would not be constant among different time periods in the natural history of established COPD. We compared the annual change rates in FEV₁ during the first 5 years and the last 5 years, estimated separately using a linear mixed-effects model in 10-year survivors (n = 110). The subjects were classified into three FEV₁ decline groups, based on the 25th and 75th percentile values in each time period. The rates of FEV₁ changes, calculated from the first 5 years and the last 5 years, did not correlate with each other among 10-year survivors; the subjects of each FEV₁ decline group during the first 5 years did not consistently remain in the same FEV₁ decline group during the last 5 years. Smoking status and exacerbation frequency were not associated with decline in FEV₁. In conclusion, the disease activity, which is often expressed as annualized change in FEV₁, might be changeable either way over years in patients with established COPD.