title: Risk factors of readmission to hospital for a COPD exacerbation: a prospective study.
abstract: BACKGROUND
  Exacerbations of chronic obstructive pulmonary disease (COPD) are a leading cause of admission to hospital among men in many countries, although the factors causing exacerbations are largely unknown. The association between readmission for a COPD exacerbation and a wide range of modifiable potential risk factors, after adjusting for sociodemographic and clinical factors, has been assessed.
  
  
  METHODS
  Three hundred and forty patients with COPD recruited during an admission for an exacerbation in four tertiary hospitals in the Barcelona area of Spain were followed for a mean period of 1.1 years. Information on potential risk factors, including clinical and functional status, medical care and prescriptions, medication adherence, lifestyle, health status, and social support, was collected at the recruitment admission. A Cox's proportional hazards model was used to obtain independent relative risks of readmission for COPD.
  
  
  RESULTS
  During the follow up period 63% of patients were readmitted at least once, and 29% died. The final multivariate model showed the following risk (or protective) factors: > or =3 admissions for COPD in the year before recruitment (hazard ratio (HR)=1.66, 95% CI 1.16 to 2.39), forced expiratory volume in 1 second (FEV(1)) percentage predicted (0.97, 95% CI 0.96 to 0.99), oxygen tension (0.88, 95% CI 0.79 to 0.98), higher levels of usual physical activity (0.54, 95% CI 0.34 to 0.86), and taking anticholinergic drugs (1.81, 95% 1.11 to 2.94). Exposure to passive smoking was also related to an increased risk of readmission with COPD after adjustment for clinical factors (1.63, 95% CI 1.04 to 2.57) but did not remain in the final model.
  
  
  CONCLUSIONS
  This is the first study to show a strong association between usual physical activity and reduced risk of readmission to hospital with COPD, which is potentially relevant for rehabilitation and other therapeutic strategies.
authors.affiliation: Respiratory and Environmental Health Research Unit, IMIM, Barcelona, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Garcia-Aymerich
authors.forename: E
authors.initials: E
authors.lastname: Farrero
authors.forename: M A
authors.initials: MA
authors.lastname: Félez
authors.forename: J
authors.initials: J
authors.lastname: Izquierdo
authors.forename: R M
authors.initials: RM
authors.lastname: Marrades
authors.forename: J M
authors.initials: JM
authors.lastname: Antó
mesh_terms: D000368:Aged; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume / Q000502:physiology; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D010359:Patient Readmission / Q000706:statistics & numerical data; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology / Q000628:therapy*; D012008:Recurrence; D012307:Risk Factors; D014797:Vital Capacity / Q000502:physiology
chemical_list: D010100:Oxygen