Objective       To investigate the clinical characteristics of asthma and chronic obstructive pulmonary disease overlap syndrome (ACOS).       Methods       A retrospective cohort of epidemiological cohort study based on our medical information database was performed on the data from those patients with airflow obstruction who were under treatment and followed up for more than 1 year. According to the diagnostic standard of COPD

asthma and ACOS

they were grouped into 3 patient cohorts. The clinical characteristics of ACOS patient cohort were analyzed

including the proportion of patients

age composition

airway inflammation type and lung function at the nearest visit

and the annual decline rate of forced expiratory volume in 1 second (FEV1).       Results       Two hundreds and forty cases were enrolled in this study who met qualifying criteria for the study. ACOS patients was identified covering 29.17%

with more male (61.4%) than female

in which 88.57% were at an age over 40

and 78.58% had postFEV1%pre 50%. There were significant differences in gender composition

median age

lung function and patients proportion of eosinophil inflammation in the airway in the ACOS cohort compared with the COPD cohort and asthma cohort (P0.05)

and these values were between those of the other 2 cohorts. Especially

the results of disease future risk assessment showed though the annual decline rate of FEV1 had no significant difference among ACOS cohort

COPD cohort and asthma cohort (P0.05)

and the annual decline absolute value of FEV1 was maximum in ACOS cohort. Moreover

the incidence of moderate and severe acute exacerbation of ACOS patients were similar to those of COPD patients

significantly higher than that of asthma patients (P0.01).       Conclusion       The clinical characteristics of ACOS patients are between those of asthma and COPD

and the disease future risk assessment are closer to COPD patients.