Which Pre-COPD Indicators Predict Lung Function Decline?

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A recent cohort study identified consistent chronic bronchitis and sSAD as the strongest predictors of lung function decline and the development of COPD.

Early identification of people at risk for COPD remains a global health priority. A prospective cohort study published in Pulmonology examined how various pre-COPD indicators relate to lung function decline and incident COPD in both smokers and non-smokers, offering actionable insights into which early respiratory changes matter most and for whom.

Liwen Fang, MD, PhD, and colleagues followed 3,526 adults (aged ≥40 years) without COPD, identified through China’s national COPD surveillance program between 2014 and 2020.

The study team assessed four pre-COPD indicators at baseline:

1. Chronic bronchitis;
2. Preserved ratio impaired spirometry (PRISm);
3. Low peak expiratory flow (PEF); and
4. Spirometric small airway dysfunction (sSAD).

Clinicians assessed lung function via post-bronchodilator FEV1, FVC, and FEV1/FVC. Participants were classified based on whether each indicator was never present, inconsistent, or consistent over time. Smoking and non-smoking participants were analyzed separately.

Indicators Linked to Decline

Among smokers, initial chronic bronchitis was associated with significantly greater annual declines in both FEV1 (−75.15 mL/year) and FVC (−77.99 mL/year). Among non-smokers, only those with consistent chronic bronchitis experienced significantly faster FEV1 and FVC decline.

Non-restrictive PRISm was associated with a faster decline in FEV1 and FVC in smokers. Among non-smokers, restrictive PRISm was linked to greater FEV1/FVC decline. However, the overall role of PRISm in predicting lung function decline was limited and variable.

Consistent sSAD was a strong predictor of FEV1/FVC decline in both smokers and non-smokers. Of note, nearly half of new COPD cases at follow-up emerged from individuals with baseline sSAD.

Smokers with consistent low PEF experienced greater FEV1/FVC decline, while this association was not significant among non-smokers.

COPD Development & Risk

During follow-up, the highest proportion of incident COPD cases emerged from people with sSAD, not from those with chronic bronchitis, PRISm, or low PEF. Among non-smokers, sSAD was associated with a threefold increased risk for developing COPD (adjusted HR, 3.12). Among smokers, chronic bronchitis, sSAD, and low PEF were all independently associated with increased COPD risk.

The study authors emphasized the clinical relevance of tracking the consistency of pre-COPD indicators over time. Chronic bronchitis among smokers and sSAD across both groups were the most reliable predictors of accelerated lung function decline. The researchers noted that chronic bronchitis may cause persistent damage in smokers even if symptoms improve later, while sSAD serves as a clearer marker for COPD progression regardless of smoking status.

This was the first longitudinal study in China to assess lung function decline using pre-COPD indicators in a general population. Its strengths included national sampling, standardized spirometry, and stratified analysis by smoking status. Limitations included reliance on only two spirometry time points, potential measurement variability, and reliance on questionnaire-based environmental exposures.

“Our study has provided evidence for the prominent pre-COPD indicators that should be considered regarding lung function decline and COPD development. Follow-up studies with longer duration are needed to investigate the changes in lung function and the underlying mechanisms for the progression to COPD among pre-COPD individuals,” Dr. Fang and colleagues concluded.