RESULTS: COPD group had more male (14/21 vs 28/75) and elderly participants (mean age 63y vs 57y) than non-COPD control groups. The baseline concentration of SP-D, body mass index, smoking (pack-years) were comparable. The overall trends observed in levels of SP-D in serum were increased in COPD and smoking control group (p<0.01), and forced expiratory volume in one second (FEV1) decreased in all groups. The rate of decline in FEV1 seemed higher in COPD patients than non-COPD control groups, but without statistical significance. After controlling for age, sex, height, body mass index, smoking, baseline level of SP-D, we found increase in SP-D is correlated with the rate of decline of FEV1 in all groups (r=0.309, p=0.005).