A Denmark retrospective study of 7 million-plus individuals found associations between increased TBI severity and frequency, and suicide risk.
Trine Madsen, PhD
Patients with traumatic brain injury (TBI) are a twice greater risk of dying from suicide than those without the condition, a retrospective cohort study of 7 million-plus Denmark residents has found.
An association between the neurologic condition and suicidality has been frequently linked by relative conditions such as post-traumatic stress disorder (PTSD) and chronic traumatic encephalopathy (CTE). But this new analysis, which covered 164,265,624 person-years of data in Denmark registries, reports an adjusted incidence rate ratio (IRR) of 1.90 (95% CI; 1.83-1.97) for suicide in patients with confirmed TBI.
Led by Trine Madsen, PhD, of the Danish Research Institute of Suicide Prevention, Mental Health Center, Copenhagen, researchers analyzed 7,418,391 individuals to have lived in Denmark between 1980-2014. Health records of each individual was collected from various registries, including the National Hospital Register, the Psychiatric Central Research Register, and the Cause of Death Register. Investigators benefitted from the fact that private psychiatric treatment does not exist in Denmark, therefore giving them full access to TBI-related data.
TBI was categorized into mild (concussion); skull fractures without documented TBI; and severe (head injuries with evidenced structural brain injury). Investigators included the following covariates when assessing the TBI-suicide association: number of medical contacts for likely distinct TBI events; accumulated number of days in hospital treatment for TBI; age at first TBI; and time since last medical contact for TBI.
Madsen told MD Magazine® that previous analysis of the TBI-suicide association—which gave considerations to the increased risk of suicide in patients with TBI who had attempted suicide prior to their injury—granted them a foundation by which to comprehensively assess the association.
Her own past work in assessing TBI in military veterans who saw combat in the Middle East gave credence to an increased risk of psychiatric illness.
“We know, especially in the US, the suicide rate has been rising—especially among the deployed and the veterans,” Madsen said. “All these things make us think, we need to do this study because we have good data and it’s an important issue.”
Among all the observed living residents, 567,823 (7.7%) had been diagnosed with TBI (mean age at first TBI, 34.3 years; 41% women). A majority of TBI diagnoses were mild (423,502). Just 24,221 (0.3%) were skull fractures, and 120,100 (1.6%) were severe TBI.
A total of 34,529 (4.7%) of observed residents died by suicide (mean age 52 years; 32.7% women), giving investigators an overall absolute rate of 21.0 per 100,000 person-years. Among all suicides, 3536 (10.2%) had previously been diagnosed with TBI—2701 with mild TBI, 174 with skull fracture, and 661 with severe TBI.
The absolute rate of suicide in individuals with hospital contact for TBI was 40.6 per 100,000 person-years, versus 19.9 per 100,000 in those with no hospital contact for TBI. In a model adjusting for sex, age, and calendar period, the IRR was 2.64 (95% CI; 2.55-2.74). In the fully adjusted model, the IRR was 1.90.
The fully adjusted model for analysis also reported an increased risk of suicide dependent on TBI diagnosis severity. Individuals the mild TBI held an absolute rate of 38.6 per 100,000 person-years and an IRR of 1.81. Individuals with skull fractures had an absolute rate of 42.4 per 100,000 and an IRR of 2.01. Individuals with severe TBI had an absolute rate of 50.8 per 100,000 and an IRR of 2.38 (P < 0.001), all compared versus individuals with no TBI.
Suicide rates were also increased for individuals with greater occurrences of medical contact for TBI. Individuals with 1 instance of contact for TBI had an IRR of 1.75, while those 2 or 3 instances of contact for TBI had IRRs of 2.31 and 2.59, respectively.
In individuals diagnosed with a psychological illness after their TBI, suicide IRR was 4.90 (P < 0.001). In individuals who engaged in deliberate self-harm prior to their TBI, suicide IRR was 7.54).
In assessing for individual demographics, particular traits were associated with a significant jump in suicide risk after TBI. Suicide rate per 100,000 person-years was 49.3 in all males with TBI, and just 27.5 in females. Divorced individuals with TBI reported a rate of 81.4, while those never married reported a rate of 32.7.
In individuals with TBI living alone, the suicide rate was 61.2 per 100,000 person-years. In individuals with TBI who were living off a disability pension, the rate was 79.4. In working individuals with TBI, it was just 14.9.
The effects of TBI on a person’s cognition state, social behavior, and frequency of headaches eventually leads to the development of psychiatric conditions, Madsen said. She expressed interest in further exploring when patients with TBI are at their most vulnerable for suicidal behavior.
“There’s far less papers on what happens to the brain’s functions, because you really need human, clinical trials to further look into that,” Madsen said.
To her perspective as a public health expert, Madsen could not speculate as to when such analysis would progress or reach real-world implication. That said, there is enough indication from this sprawling retrospective study for her to advise individuals on caring for patients with TBI.
“You should look for that person developing psychiatric conditions, and for seeking care for them,” Madsen said. “Of course, we should be looking for ways to prevent TBI.”
The study, "Association Between Traumatic Brain Injury and Risk of Suicide," was published online in JAMA on Tuesday.