Madsen T, et al. - In this nationwide registry-based retrospective cohort study, researchers explored the link between traumatic brain injury (TBI) and subsequent suicide. Compared with the general population without TBI people with medical contact for TBI had increased suicide risk.

Methods

• Using nationwide registers, a retrospective cohort study was conducted covering 7,418,391 people (≥ 10 years) living in Denmark (1980-2014) with 164,265,624 person-years’ follow-up; of them, 567,823 (7.6%) had a medical contact for TBI.
• Utilizing Poisson regression adjusted for relevant covariates, data were analyzed including fractures not involving the skull, psychiatric diagnoses, and deliberate self-harm.
• Main exposures analyzed were medical contacts for TBI recorded in the National Patient Register (1977-2014) as mild TBI (concussion), skull fracture without documented TBI, and severe TBI (head injuries with evidence of structural brain injury).
• Suicide recorded in the Danish Cause of Death register until December 31, 2014 was the main outcome.

Results

• According to the findings obtained, out of 34,529 people who died by suicide (mean age, 52 years [SD, 18 years]; 32.7% women; absolute rate 21 per 100,000 person-years [95% CI, 20.8-21.2]), 3,536 (10.2%) had medical contact: 2,701 with mild TBI, 174 with skull fracture without documented TBI, and 661 with severe TBI.
• It was observed that the absolute suicide rate was 41 per 100,000 person-years (95% CI, 39.2-41.9) among those with TBI compared with 20 per 100,000 person-years (95% CI, 19.7-20.1) among those with no diagnosis of TBI.
• Findings revealed that compared with those without TBI, severe TBI (absolute rate, 50.8 per 100,000 person-years; 95% CI, 46.9-54.6) was related to an IRR of 2.38 (95% CI, 2.20-2.58), whereas mild TBI (absolute rate, 38.6 per 100,000 person-years; 95% CI, 37.1-40.0), and skull fracture without documented TBI (absolute rate, 42.4 per 100,000 person-years; 95% CI, 36.1-48.7) had an IRR of 1.81 (95% CI, 1.74-1.88) and an IRR of 2.01 (95% CI, 1.73-2.34), respectively.
• Data reported that suicide risk was related to number of medical contacts for TBI vs those with no TBI contacts: one TBI contact, absolute rate, 34.3 per 100,000 person-years (95% CI, 33.0-35.7; IRR, 1.75; 95% CI, 1.68-1.83); two TBI contacts, absolute rate, 59.8 per 100,000 person-years (95% CI, 55.1-64.6; IRR, 2.31; 95% CI, 2.13-2.51); and three or more TBI contacts, absolute rate, 90.6 per 100,000 person-years (95% CI, 82.3-98.9; IRR, 2.59; 95% CI, 2.35-2.85; all P
• They found that compared with the general population, temporal proximity since the last medical contact for TBI was related to risk of suicide (P < .001), with an IRR of 3.67 (95% CI, 3.33-4.04) within the first 6 months and an incidence IRR of 1.76 (95% CI, 1.67-1.86) after 7 years.