title: Post-hospital syndrome in adults with asthma: a case-crossover study.
abstract: BACKGROUND
  Post-hospital syndrome refers to the period of generalized risk of adverse health outcomes among patients who are recently discharged from hospital. This period is associated with a short-term increased risk of readmission which may not be related to the original condition. While the majority of studies of post-hospital syndrome have focused on all-cause readmissions, whether and to what extent such a phenomenon exists within discrete medical conditions is not yet known.
  
  
  OBJECTIVE
  To investigate whether the risk of admission due to asthma is increased in individuals who are discharged following any-cause hospital admission.
  
  
  METHODS
  Using administrative health data for the period 1997 to 2007 from the province of British Columbia, Canada, we created a cohort of adults with asthma. Using a case-crossover design, we assessed the association between discharge from a hospital (exposure) within 30 days before an asthma-related hospitalization (the outcome), using two 30-day control periods within the same subject. Conditional logistic regression was performed to calculate the relative risk (RR) of the outcome in association with exposure. We performed several sensitivity and subgroup analyses.
  
  
  RESULTS
  The final cohort included 3,852 patients experiencing 6,333 instances of the outcome. Mean age at the time of the outcome was 43.7 (SD 14.2), 69.0% of such outcomes belonged to females. The RR of the outcome within the next 30 days of a previous any-cause discharge was 1.40 (95% CI 1.22 - 1.59). However, the association was mainly caused by discharge from asthma-related admission [RR = 1.99 (95% CI 1.65 - 2.39)]. The RR associated with non-asthma-related discharge was 0.88 (95% CI 0.74 - 1.04) and was not statistically significant. Similar results were obtained in a range of sensitivity analyses.
  
  
  CONCLUSIONS
  Our results indicate that in patients with asthma, the 30-day risk of asthma-related admission is increased after an episode of asthma-related hospitalization, but not after an episode of non-asthma-related hospitalization.
authors.affiliation: Department of Medicine, Institute for Heart and Lung Health, The University of British Columbia, 7th Floor, 828 West 10th Avenue, Research Pavilion, Vancouver V5Z 1 M9, Vancouver, BC, Canada. msafavi@mail.ubc.ca.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Sadatsafavi
authors.forename: Larry D
authors.initials: LD
authors.lastname: Lynd
authors.forename: J Mark
authors.initials: JM
authors.lastname: Fitzgerald