Of 1679 people screened at homeless shelters and meal programs, we included 904 people in our study (). In total, 489 (29%) were ineligible for inclusion: 222 (13%) did not meet our definition of homelessness, 61 (4%) were unable to communicate in English, 54 (3%) were homeless shelter users encountered at meal programs, and 51 (3%) were unable to give informed consent. Because this study was part of a larger study of the utilization of health care by homeless people, we excluded 101 people (6%) because they did not have an Ontario health insurance number. Most of these 101 people were refugees, refugee claimants or had recently migrated to Ontario. Of 1190 eligible people, 283 declined to participate. We enrolled 907 (76% of eligible people) in the study. We obtained information about traumatic brain injury for 904 participants. Characteristics of study participants are shown in .
Figure 1: Flow diagram of participant recruitment.
The lifetime prevalence of traumatic brain injury was 53%. The prevalence was significantly higher among men (58%) than among women (42%, p < 0.001). Those with a history of traumatic brain injury were more likely to be male, white and born in Canada; to have become homeless for the first time at a younger age; and to have experienced more years of homelessness over their lifetime. Compared to those without a history of traumatic brain injury, participants with a history of traumatic brain injury had a significantly higher lifetime prevalence of seizures (8% v. 22%, p < 0.001); higher prevalence of mental health problems (33% v. 43%, p = 0.001), alcohol problems (28% v. 42%, p < 0.001) and drug problems (40% v. 57%, p < 0.001). They also had poorer mental health (mean score 43.8 v. 39.0, p < 0.001) and physical health (mean score 48.1 v. 43.9, p < 0.001) as measured by the SF-12 health survey ().
The mean age at first traumatic brain injury was 17.8 years. Although 40% of participants with traumatic brain injuries reported only 1 such injury, 21% reported 2 injuries, 12% reported 3 injuries, 7% reported 4 injuries, and 20% reported 5 or more injuries. The severity of the worst traumatic brain injury was mild for 66% of participants, moderate or severe for 23% and unknown for 11%. In all analyses involving traumatic brain injury severity, we grouped injuries of unknown severity with mild injuries. Analyses in which injuries of unknown severity were considered to be a separate category gave essentially identical results.
The temporal relation between the first traumatic brain injury and the first episode of homelessness is shown in . For 70% of participants, the first traumatic brain injury occurred before the onset of homelessness. The injury occurred in the same year as the onset of homelessness for 7% of participants, and after the onset of homelessness for 22%. We could not determine the relation between the first traumatic brain injury and the first episode of homelessness for 2% of participants.
Figure 2: Homeless participants (n = 461) who experienced a traumatic brain injury before or after becoming homeless.
When we considered the influence of sex, age, ethnic background, place of birth, education and lifetime years of homelessness, a history of traumatic brain injury was significantly associated with seizures, mental health and drug problems, and poorer physical and mental health status (). In additional models that included both the severity of the worst traumatic brain injury and the total lifetime number of traumatic brain injuries as covariables, a higher number of traumatic brain injuries was associated with significantly increased odds of seizures and mental health, alcohol and drug problems.