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Accelerated lung function decline does not always lead to COPD

A large portion of people who have low forced expiratory volume in 1 second in early adulthood develop COPD later in life, according to study results.

However, the researchers noted it does not always mean an accelerated decline in lung function leads to COPD.

“The main new finding of this study is that the lung-function value reached in early adulthood seems to be important with respect to the diagnosis of COPD later in life,” Peter Lange, MD, a professor in the Section of Social Medicine at the University of Copenhagen, and colleagues wrote. “Our data suggest that approximately half the persons presenting with airflow limitation followed the paradigm that implied a rapid decline in [forced expiratory volume in 1 second (FEV₁)] from a normal level of lung function in early adulthood, whereas the other half had a rather normal decline in FEV₁ but started from a low initial value of FEV₁.”

Lange and colleagues used the data from three independent cohort studies and analyzed the combined rate of decline in FEV₁ among 495 current or former smokers aged 50 to 65 years who had a Global Initiative for Chronic Obstructive Lung Disease grade two or higher.

The researchers also divided the participants from the cohorts according to lung function at the beginning of each study and the existence or lack of COPD at the last study visit.

Twenty-six percent of participants who had a FEV₁ of less than 80% predicted value (n = 657) before age 40 years had COPD after two decades of observation.

However, 7% of participants (n = 2,207) who had a baseline FEV₁ of at least 80% of the predicted value before 40 had COPD after two decades of observation.

Less than half (48%) of 332 people with COPD at final examination followed a path of normal FEV₁ at baseline to COPD, with an average decline in FEV₁ of 53 mL.

In comparison, the remaining followed the FEV₁ path from predicted value less than 80% as baseline to COPD, with a decline in FEV₁ of 27 mL per year (P < .001).

The researchers did acknowledge some limitations to the study including age of participants as baseline in two of the cohorts.

“[A] potential methodologic weakness of [two studies] concerns the age of participants, [35 years], at baseline,” the researchers wrote. “Although this age corresponds to the last part of the ‘plateau phase’ of FEV₁, it would have been preferable if the participants had undergone spirometry in their mid-20s, so that the potential influence of an incipient decline in FEV₁ during early adulthood could be avoided.” – by Ryan McDonald