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 < or =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.