Decline in FEV₁ in Relation to Incident Chronic Obstructive Pulmonary Disease in a Cohort with Respiratory Symptoms

Abstract

Data on the relationship between decline in lung function and development of COPD are sparse. We assessed the decline in FEV₁ during 10 years among subjects with respiratory symptoms by two different methods and evaluated risk factors for decline and its relation to incident Chronic Obstructive Pulmonary Disease, COPD. A cross-sectional postal questionnaire was in 1986 sent to 6610 subjects of three age strata. All subjects reporting respiratory symptoms were invited to a structured interview and spirometry. A follow-up survey was performed 10 years later, and totally 1109 subjects performed spirometry in both 1986 and 1996. COPD was defined according to the ATS/ERS standards (FEV₁/FVC ≤0.70). The decline in FEV₁ was 39 ml/year in men vs. 28 ml/year in women, p = < 0.001 (−1.53 vs. −0.12 change in percent of predicted normal value over 10 years (pp), p = 0.023), among smokers 39 vs. non-smokers 28 ml/year, p < 0.001 (−3.30 vs. 0.69 pp, p < 0.001), in subjects with chronic productive cough 36 vs. not 32 ml/year, p = 0.044 (−2.00 vs. −0.02 pp, p = 0.002). Incident cases of moderate COPD (n = 83) had a decline of 62 ml/year (−12.6 pp) and 22.9% of them had a decline > 90 ml/year (−27.8 pp over 10 years). Gender-specific analysis revealed that smoking was a stronger risk factor in women than in men, while higher age was a significant risk factor in men only. In conclusion, decline in FEV₁ was associated with age, smoking, and chronic productive cough, but the risk factor pattern was gender-dependent. Among incident cases of COPD the decline was steeper and close to a quarter had a rapid decline.

Key words: :

• Incidence
• COPD
• Decline in FEV₁
• Risk factors
• Respiratory symptoms
• Gender