title: Comorbidity as a contributor to frequent severe acute exacerbation in COPD patients.
abstract: BACKGROUND
  Comorbidities have a serious impact on the frequent severe acute exacerbations (AEs) in patients with COPD. Previous studies have used the Charlson comorbidity index to represent a conglomerate of comorbidities; however, the respective contribution of each coexisting disease to the frequent severe AEs remains unclear.
  
  
  METHODS
  A retrospective, observational study was performed in 77 COPD patients who experienced severe AE between January 2012 and December 2014 and had at least 1-year follow-up period from the date of admission for severe AE. We explored the incidence of frequent severe AEs (≥2 severe AEs during 1-year period) in these patients and investigated COPD-related factors and comorbidities as potential risk factors of these exacerbations.
  
  
  RESULTS
  Out of 77 patients, 61 patients (79.2%) had at least one comorbidity. During a 1-year follow-up period, 29 patients (37.7%) experienced frequent severe AEs, approximately two-thirds (n=19) of which occurred within the first 90 days after admission. Compared with patients not experiencing frequent severe AEs, these patients were more likely to have poor lung function and receive home oxygen therapy and long-term oral steroids. In multiple logistic regression analysis, coexisting asthma (adjusted odds ratio [OR] =4.02, 95% confidence interval [CI] =1.30-12.46, P=0.016), home oxygen therapy (adjusted OR =9.39, 95% CI =1.60-55.30, P=0.013), and C-reactive protein (adjusted OR =1.09, 95% CI =1.01-1.19, P=0.036) were associated with frequent severe AEs. In addition, poor lung function, as measured by forced expiratory volume in 1 second (adjusted OR =0.16, 95% CI =0.04-0.70, P=0.015), was inversely associated with early (ie, within 90 days of admission) frequent severe AEs.
  
  
  CONCLUSIONS
  Based on our study, among COPD-related comorbidities, coexisting asthma has a significant impact on the frequent severe AEs in COPD patients.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Suk Hyeon
authors.initials: SH
authors.lastname: Jeong
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Hyun
authors.initials: H
authors.lastname: Lee
authors.affiliation: Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada; Biostatistics and Clinical Epidemiology Center, Samsung Medical Center, Seoul, South Korea.
authors.forename: K C
authors.initials: KC
authors.lastname: Carriere
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Sun Hye
authors.initials: SH
authors.lastname: Shin
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Seong Mi
authors.initials: SM
authors.lastname: Moon
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Byeong-Ho
authors.initials: BH
authors.lastname: Jeong
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Won-Jung
authors.initials: WJ
authors.lastname: Koh
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Hye Yun
authors.initials: HY
authors.lastname: Park
mesh_terms: D000284:Administration, Oral; D000368:Aged; D001249:Asthma / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology / Q000628:therapy; D016009:Chi-Square Distribution; D015897:Comorbidity; D018450:Disease Progression; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008168:Lung / Q000503:physiopathology*; D008297:Male; D015999:Multivariate Analysis; D016017:Odds Ratio; D010102:Oxygen Inhalation Therapy; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology / Q000628:therapy; D056910:Republic of Korea / Q000453:epidemiology; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D013256:Steroids / Q000008:administration & dosage; D013997:Time Factors
chemical_list: D013256:Steroids
keywords: asthma; chronic obstructive pulmonary disease; comorbidity; exacerbation