Change in pulmonary diffusion capacity in a general population sample over 9 years

RATIONALE: Data on the change in diffusion capacity of the lung for carbon monoxide (DL(CO)) over time are limited. We aimed to examine change in DL(CO) (ΔDL(CO)) over a 9-year period and its predictors. METHODS: A Norwegian community sample comprising 1,152 subjects aged 18–73 years was examined in 1987 and 1988. Of the 1,109 subjects still alive, 830 (75%) were re-examined in 1996/97. DL(CO) was measured with the single breath-holding technique. Covariables recorded at baseline included sex, age, height, weight, smoking status, pack years, occupational exposure, educational level, and spirometry. Generalized estimating equations analyses were performed to examine relations between ΔDL(CO) and the covariables. RESULTS: At baseline, mean [standard deviation (SD)] DL(CO) was 10.8 (2.4) and 7.8 (1.6) mmol·min(−1)·kPa(−1) in men and women, respectively. Mean (SD) ΔDL(CO) was −0.24 (1.31) mmol·min(−1)·kPa(−1). ΔDL(CO) was negatively related to baseline age, DL(CO), current smoking, and pack years, and positively related to forced expiratory volume in 1 second (FEV(1)) and weight. Sex, occupational exposure, and educational level were not related to ΔDL(CO). CONCLUSIONS: In a community sample, more rapid decline in DL(CO) during 9 years of observation time was related to higher age, baseline current smoking, more pack years, larger weight, and lower FEV(1).