Chan et al. BMC Res Notes (2017) 10:371 DOI 10.1186/s13104-017-2682-x RESEARCH NOTE Clinical profle and comorbidity of traumatic brain injury among younger and older men and women: a brief research notes Vincy Chan 1,2 , Tatyana Mollayeva 1,2* , Kenneth J. Ottenbacher 3 and Angela Colantonio 1,2 Abstract Objective: Comorbid disorders influence the course and outcomes of rehabilitation following traumatic brain injury (TBI), yet sex- and age-related disparities in the frequency distribution of these disorders remain poorly understood. We aimed to describe comorbid disorders by the International Classification of Diseases in patients with TBI undergo- ing inpatient rehabilitation in Ontario, Canada over a 3-year period, by sex and age, and discuss their potential impact on rehabilitation outcomes. Results: The percentage of TBI patients with one or more comorbid disorder is higher among older (≥65 years) men and women than among those who are younger or middle-aged (<65 years). Among younger and middle-aged patients, multiple injuries and trauma, mental health conditions, and nervous system disorders were the most preva- lent comorbidities. In older patients, circulatory, endocrine, nutritional, metabolic, and immune disorders were the most prevalent comorbidities. Our results suggest that a multisystem view of rehabilitation of men and women with TBI across age categories is needed to reflect the complex clinical profile of TBI patients undergoing rehabilitation. Keywords: Traumatic brain injury, Inpatient rehabilitation, Sex, Age, Index disease, Comorbidity, Multimorbidity, Prevalence © The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Introduction Traumatic brain injury (TBI), defned as “a traumatically induced structural injury and/or physiological disrup- tion of brain function as a result of an external force” [1], remains a signifcant public health issue [2, 3]. Recent ini- tiatives in TBI care highlight the complexity of its clinical management, and recommend that an assessment of co- existing (comorbid) disorders be included [4]. “Comor- bidity” refers to any disease co-existing with an index disease [5]; it can alter the clinical course of patients by afecting selections of healthcare services and out- comes [6, 7]. While previous population-based research from United States and Canada [8–12] has documented comorbidities in TBI, there has been no comprehensive description of sex- and age- specifc clinical nosolo- gies for TBI patients entering inpatient rehabilitation. Historically, TBI has been regarded as an injury mostly afecting young males [13]. However, recent epidemio- logical trends highlight older females being as frequently afected as males, largely as a result of falls [13]. Because many diseases afecting males and females have difer- ent frequencies and presentations across their lifespan [14, 15], understanding the variability of comorbidity in rehabilitation [12, 14, 15] will likely lead to a still greater recognition of the unique sex-specifc facets of TBI [16, 17]. Terefore, the aims of this study were to: (1) describe comorbidity frequencies (along the spectrum of disor- ders) in younger and older patients, by sex; (2) assess pos- sible sex diferences in comorbid disorder frequencies; Open Access BMC Research Notes *Correspondence: tatyana.mollayeva@utoronto.ca 2 Rehabilitation Sciences Institute, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada Full list of author information is available at the end of the article