title: Application of hurdle model with random effects for evaluating the balance improvement in stroke patients.
abstract: BACKGROUND
  Stroke is a prevalent cause of disability in adults. The fall is the most common balance and motor impairments, which affects the quality of life in stroke patients. This study aims to employ random effects hurdle model for evaluating the balance improvement in stroke patients under the occupational therapy.
  
  
  METHODS
  In this longitudinal study with repeated measurement during one year between 2013 and 2014, the data was collected using non-random sampling method from three occupational therapy clinics. For a total of 38 stroke patients, the number of falls was recorded every two weeks. The random effects hurdle model and random effects zero inflated Poisson (ZIP) model were fitted to the data and were compared together. Data analysis was carried out using SAS Software version 9.2.
  
  
  RESULTS
  The results of random effects ZIP model showed that the covariates of sex and age and affected side of stroke and follow up duration had statistically significant effect on balance improvement (p< 0.05). The occupational therapy has been effective on balance improvement more than 40% during one year.
  
  
  CONCLUSIONS
  The ZIP model with random effects can capture zero inflation and correlation structure in longitudinal count data simultaneously. Older patients, women and patients with left-side impairments were more at risk of fall and balance impairment, so they need more care and therapy.
authors.affiliation: Associate Professor of Biostatistics, Department of Basic Sciences, Faculty of rehabilitation Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Akbarzad@sbmu.ac.ir.
authors.forename: Alireza
authors.initials: A
authors.lastname: Akbarzadeh Baghban
authors.affiliation: MSc of Biostatistics, Department of Biostatistics, School of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Ahmadisomayeh90@gmail.com.
authors.forename: Somayeh
authors.initials: S
authors.lastname: Ahmadi Gooraji
authors.affiliation: Assistant Professor of Statistics, Department of Basic Sciences, Faculty of Health Safety and Environment, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Kavousi@sbmu.ac.ir.
authors.forename: Amir
authors.initials: A
authors.lastname: Kavousi
authors.affiliation: MSc of Occupational therapy, Department of Occupational Therapy, Faculty of rehabilitation sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Mirzakhany@yahoo.com.
authors.forename: Navid
authors.initials: N
authors.lastname: Mirzakhani Araghi
keywords: Balance; Occupational therapy; Stroke