1. This retrospective cohort study found that, in comparison to the total US population, post-9/11 military veterans exposed to traumatic brain injury (TBI) experienced greater excess all-cause and cause-specific mortality.

2. Military veterans exposed to moderate to severe TBI in particular, accounted for the highest percentage of total excess deaths observed.

Evidence Rating Level: 2 (Good)

Study Rundown: Exposure to traumatic brain injury (TBI) has been linked to an increase in mental health diagnoses, various chronic conditions and premature death, however the risk of mortality in post-9/11 military veterans is unknown. This cohort study analyzed data collected from the Department of Defense Military Health System between 2002 and 2018 for US military veterans who actively served and received care during the Global War on Terror post-9/11 in comparison to the total US population. Among 2,516,189 military veterans aged 18-84 years, there were an estimated 3858 excess deaths of which 2285 individuals had mild TBI and 1298 individuals had moderate to severe TBI. Differences in the adjusted all-cause mortality rate between veterans and the total US population were greatest among veterans aged 75-84 years.. Exposure to moderate to severe TBI in military veterans contributed to a statistically significant increased risk in all-cause mortality including cardiovascular disease (CVD) and other chronic diseases compared to the total US population. Military veterans not exposed to TBI experienced mortality advantages for CVD and other causes. These results suggest that TBI is associated with long-term health risks for military veterans including accelerating aging, increasing cardiovascular mortality, and chronic disease mortality. One strength of this study was its particularly large sample size, allowing the detection of more granular differences in populations. A limitation to the study is that the data analyzed was not detailed enough to investigate the reasons for increased health and mortality risks linked to TBI. This presents an area of study for further research.

Click to read the study in JAMA Network Open

Click to read an accompanying editorial in JAMA Network Open

Relevant Reading: Association of mild traumatic brain injury with and without loss of consciousness with dementia in US military veterans

In-Depth [retrospective cohort]: This cohort study included 2,516,189 veterans who served active duty in the military post-9/11 (348,458 [13.8%] female) with no TBI (n=1,999,729), mild TBI (n=441,083) or moderate to severe TBI (n=75,377) and compared them with the total US population (n= 229,104,796). Both the post-9/11 military veteran population and the total US population were observed from 2002 to 2018. Among all military veterans included, there were 3858 (95% CI, 1225 to 6490) excess deaths, of which 275 (95% CI, -1435 to 1985) had no TBI exposure, 2285 (95% CI, 1637 to 2933) had mild TBI, and 1298 (95% CI, 1023 to 1572) had moderate to severe TBI. The military veteran population exposed to moderate to severe TBI accounted for 33.6% of total excess deaths observed. All-cause mortality rates monotonically increased with TBI severity and were higher for military veterans in comparison to the total US population. Crude all-cause mortality rates for military veterans with no TBI, mild TBI, or moderate to severe TBI were 173.0 vs 225.4 vs 394.5 per 100,000 person-years respectively. The multivariable, sex-specific, adjusted all-cause mortality rate between the total US population and military veterans without TBI, mild TBI and moderate to severe TBI was 6305.7 vs 8902.0 vs 17,009.5 per 100,000 person-years respectively. For those military veterans not exposed to TBI, mortality advantages for CVD (-1150; 95% CI, -1344 to -955) and all other causes (-2669; 95% CI, -2907 to -2430) were observed.

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