Association of Traumatic Brain Injury With Mortality Among Military Veterans Serving After September 11, 2001

Abstract

Importance: Emerging evidence suggests that harmful exposures during military service, such as traumatic brain injury (TBI), may contribute to mental health, chronic disease, and mortality risks.

Objective: To assess the mortality rates and estimate the number of all-cause and cause-specific excess deaths among veterans serving after the September 11, 2001, terrorist attacks (9/11) with and without exposure to TBI.

Design, setting, and participants: This cohort study analyzed administrative and mortality data from January 1, 2002, through December 31, 2018, for a cohort of US military veterans who served during the Global War on Terrorism after the 9/11 terrorist attacks. Veterans who served active duty after 9/11 with 3 or more years of care in the Military Health System or had 3 or more years of care in the Military Health System and 2 or more years of care in the Veterans Health Administration were included for analysis. The study used data from the Veterans Affairs/Department of Defense Identity Repository database, matching health records data from the Military Health Service Management Analysis and Reporting tool, the Veterans Health Administration Veterans Informatics and Computing Infrastructure, and the National Death Index. For comparison with the total US population, the study used the Centers for Disease Control and Prevention WONDER database. Data analysis was performed from June 16 to September 8, 2021.

Exposure: Traumatic brain injury.

Main outcomes and measures: Multivariable, negative binomial regression models were used to estimate adjusted all-cause and cause-specific mortality rates for the post-9/11 military veteran cohort, stratified by TBI severity level, and the total US population. Differences in mortality rates between post-9/11 military veterans and the total US population were used to estimate excess deaths from each cause of death.

Results: Among 2 516 189 post-9/11 military veterans (2 167 736 [86.2%] male; and 45 324 [1.8%] American Indian/Alaska Native, 160 178 [6.4%], Asian/Pacific Islander, 259 737 [10.3%] Hispanic, 387 926 [15.4%] non-Hispanic Black, 1 619 834 [64.4%] non-Hispanic White, and 43 190 [1.7%] unknown), 17.5% had mild TBI and 3.0% had moderate to severe TBI; there were 30 564 deaths. Adjusted, age-specific mortality rates were higher for post-9/11 military veterans than for the total US population and increased with TBI severity. There were an estimated 3858 (95% CI, 1225-6490) excess deaths among all post-9/11 military veterans. Of these, an estimated 275 (95% CI, -1435 to 1985) were not exposed to TBI, 2285 (95% CI, 1637 to 2933) had mild TBI, and 1298 (95% CI, 1023 to 1572) had moderate to severe TBI. Estimated excess deaths were predominantly from suicides (4218; 95% CI, 3621 to 4816) and accidents (2631; 95% CI, 1929 to 3333). Veterans with moderate to severe TBI accounted for 33.6% of total excess deaths, 11-fold higher than would otherwise be expected.

Conclusions and relevance: This military veteran cohort experienced more excess mortality compared with the total US population than all combat deaths from 9/11/01 through 9/11/21, concentrated among individuals exposed to TBI. These results suggest that a focus on what puts veterans at risk for accelerated aging and increased mortality is warranted.

Figure 1.. Study Flow Diagram

MHS indicates Military Health System; NDI, National Death Index; SSN, Social Security number; VADIR, Veterans Affairs/Department of Defense Identity Repository; and VHA, Veterans Health Administration.

Figure 2.. Multivariable Adjusted, Age-Specific All-Cause Mortality Rates per 100 000 Person-Years by Population Subgroups

Shaded areas indicate 95% CIs.

Figure 3.. Multivariable Adjusted, Age-Specific Mortality Rates per 100 000 Person-Years

Shaded areas indicate 95% CIs; CVD, cardiovascular disease; TBI, traumatic brain injury.