Patients with a traumatic brain injury (TBI) who develop post-traumatic stress disorder (PTSD) are more likely to have worse cognitive function and more health problems a year later, new research suggests.
"PTSD takes the day with regard to health outcomes, including cognitive impairment, across four subgroups of TBI severity," Dr Douglas F. Zatzick said.
Dr Zatzick, lead author of the study in the Archives of General Psychiatry, is with the University of Washington School of Medicine in Seattle.
Recent studies of soldiers with mild TBI indicate that PTSD independently contributes to worse outcomes. The current research, based on the prospective National Study on the Costs and Outcomes of Trauma (NSCOT), extends those findings to include the full spectrum of TBI, Dr Zatzick said.
The results also support the theory that greater TBI severity lowers the risk of PTSD, most likely because these patients can't remember the distressing event as well, he added.
The research team studied outcomes for 3047 civilian patients (ages 18 to 84) hospitalised at 69 US hospitals with moderate to severe injuries who survived for at least a year.
Results of tests
Based on Maximum Abbreviated Injury Scale scores, 20.5% of patients had experienced severe TBI, 11.7% moderate TBI, 12.9% mild TBI, and 54.9% no TBI.
Investigators determined cognitive function during telephone interviews using a 4-item assessment (reasoning and problem-solving, memory, attention, and concentration and thinking). They determined symptoms of PTSD with the civilian version of the PTSD Checklist, a 17-item self-report questionnaire.
At 12 months, 602 patients were diagnosed with PTSD, including 24.1% of patients with no TBI, 22.7% of those with mild TBI, 18.8% with moderate TBI and 16.8% with severe TBI.
Compared with no TBI, moderate TBI was associated with a hazard ratio of 0.63, and severe TBI with an HR of 0.72, after adjusting for socio-demographics and clinical factors. The difference between mild and no TBI didn't differ significantly.
"The diminished risk of PTSD by TBI severity is consistent with the possibility that the mechanism involves impaired consolidation of traumatic memories," the investigators suggest.
Head and spinal injuries
The authors report for the first time that severe facial and spinal cord injuries were also associated with an increased risk of PTSD (aHR 1.38 and 1.32, respectively).
Patients with moderate and severe head injuries demonstrated the lowest cognitive scale scores and more gradual cognitive improvements after a year (p < 0.001 for both).
Nevertheless, regardless of TBI severity, those with PTSD demonstrated significantly lower cognitive scores compared with patients without PTSD (all p < 0.001).
Average cognitive scale scores ranged from about 78 to 84 out of 100 in the no-PTSD group, and from about 40 to 60 in patients with PTSD.
Dr Zatzick's group observed a similar pattern for health outcomes as measured by SF-36 subscale scores.
They note that their study didn't include such factors as duration of coma, posttraumatic amnesia, or neuropsychological or neuro-radiologic evaluations. Also, they say that they "cannot rule out the possibility that self-reported health and cognitive impairments could be contributing to the worsening of PTSD symptoms."
Still, they conclude, "treatment programs for the full spectrum of injured patients with mild, moderate, and severe TBI could productively integrate multifaceted interventions targeting PTSD."
"Depression after TBI would be important to look at as well," Dr. Zatzick added.
(Reuters Health, Karla Gale, December 2010)