Evaluation of Stratified Cox Model in Identifying the Factors Associated with Readmission of Asthma Patients

Background and Asthma is one of the most common chronic diseases worldwide and its prevalence has increased over the past decades in industrialized and developing countries. Cox proportional hazards model is one of the main models used in the analysis of survival data. This study was performed to evaluate the Stratified cox model in identifying the factors influencing readmission of asthma patients in Sanandaj Besat Hospital. In a retrospective study, 301 records of asthma patients hospitalized during 2005 -2012 in Sanandaj’s Besat Hospital were reviewed, and information was extracted in a check list. Data was then fitted to R 2.14.0 stratified Cox model. By using Goodness-of-fit test (GOF) Proportional Hazard (PH) assumption was tested. PH assumption was true for all variables, except for dust and marital status. Fitted stratified Cox model showed occupational exposure, viral infections, and PM10 with significant effect on the time of readmission (P <0.05). In this study occupational exposure (such as farms and contact with chemical materials), viral infections, and PM10 were significant factors associated with readmission of asthma patients. Therefore, it is recommended to focus more on principles of occupational health, practicing personal hygiene in exposure to viral infections and caring for people with asthma on polluted days.