Table 1.

Key studies of long-term functional outcome and mortality after traumatic brain injury.

Study	Study design	Sample	Follow-up*	Outcomes	Main findings	Risk factors
Whitnall et al (2006)39 Glasgow, UK	Prospective cohort study	475 adults who were admitted to hospital for TBI (all severities) and were alive 1 year after injury; 58% aged ≤ 40 years at injury	5–7 years	Mortality, functional outcome, cognition, emotional adjustment, health status, alcohol and drug use, and social deprivation	24% of patients had died by 5–7 years; 53% of survivors were disabled, 29% had improved and 25% deteriorated by follow-up at 5–7 years.	Disability was more strongly related to emotional adjustment and self-esteem than to injury severity or cognitive impairment.
McMillan et al (2012)40 Glasgow, UK	Prospective cohort study	219 adults who were admitted to hospital for TBI (all severities) and were alive at 5–7 years after injury; 65% aged ≤ 40 years at injury	12–14 years	Mortality, functional outcome, cognition, emotional adjustment, health status, alcohol use, and social deprivation	16% of patients had died by 12–14 years; 51% of survivors were disabled, 23% had improved, and 32% had deteriorated by follow-up at 12–14 years	Disability was associated with older age at injury, premorbid brain illness or physical disability and current self-esteem and stress.
McMillan et al (2014)28 Glasgow, UK	Prospective case-controlled, record linkage study	2,428 adults who were admitted to hospital for mild TBI; median age 39 years at injury; 2428 individuals without TBI in the community, matched for age, sex, and social deprivation	15 years	Mortality	37% of patients had died by follow up at 15 years; death rate was 24.5 per 1,000 patients versus 13.3 per 1000 community controls (ratio=1.84).	Age was a risk factor for mortality; younger adults with TBI had a 4.2 times greater risk of death than community controls; in addition to age, independent risk factors at time of injury included habitual alcohol excess, number of previous admissions to hospital with TBI, preinjury physical limitations, and social deprivation.
Corrigan et al (2014)43 TBI Model Systems national database, USA	Prospective cohort study	4064 adults who received inpatient rehabilitation for TBI; 53% aged <60 years at injury	5 years	Mortality, functional outcome, societal participation, emotional adjustment, and alcohol and drug use	Estimated that for the US acute inpatient rehabilitation population 21% had died by 5 years; 57% of survivors were disabled and 39% had deteriorated since 1–2 years after injury	Poorer functional outcome was associated with older age, whereas younger groups had poorer mental health and emotional outcomes.
Pretz et al (2013)41 and Dams-O’Connor et al (2015)42 TBI Model Systems national database, USA	Prospective cohort study	3,870 adults who received inpatient rehabilitation for TBI; mean age 36 at injury years at injury	1–20 years	Mortality, functional outcome	Group mean outcome ratings were in the moderately disabled range at all time points; functional outcome improved initially, reached a peak at about 10 years after injury, then subsequently declined.	Growth curves were influenced by age, race, disability at admission, and length of rehabilitation stay; trajectories for those who died at least 5 years after injury began with lower functional status and declined more rapidly than trajectories for those who survived.
Harrison-Felix et al (2012)27,44 TBI Model Systems national database, USA	Prospective cohort study	8,573 adults who received inpatient rehabilitation for TBI; mean age at injury 39 years	1–20 years	Mortality, life expectancy, cause of death	Patients with TBI were 2.25 times more likely to die than the general population (adjusted for age, sex, and race or ethnicity). SMR was elevated in all subgroups (age, gender, race, and injury severity), and remained higher 10 years after injury; SMR was raised for all causes of death, particularly seizures (33.38), aspiration pneumonia (13.35), sepsis (10.37), accidental poisonings (9.54), and falls (9.87)	Independent risk factors for death included: older age, being a man, non-Hispanic ethnicity, being unemployed or unmarried at injury, preinjury drug use, and greater disability at discharge; risk factors for mortality varied by age group. Increased deaths in younger age groups were mainly due to external causes and accidents; life expectancy in the youngest men was decreased by 16 years.
Baguley et al (2012)45 and Nott et al (2012)46 NSW, Australia	Prospective cohort, record linkage study.	2,545 adults who received inpatient rehabilitation for severe TBI; mean age 35 years at injury	2–20 years	Mortality	Overall mortality was 10% and patients with TBI were 3·19 times more likely to die than the general population (adjusted for age and sex); risk of death was increased for 8 years or more after discharge; SMR was raised for causes of death related to abnormal clinical and laboratory findings (14.1), respiratory system (10.2), nervous system (6.4), digestive system (5.2), mental and behavioural disorders (5.4), and external causes (5.2).	Independent risk factors included disability at discharge, older age at injury, being a man, preinjury drug and alcohol misuse, preinjury epilepsy, and discharge to an aged care facility; crude mortality rates increased with age, but younger adults had the highest risk of death compared with population norms.
Flaada et al (2007)47 Olmsted County, MN, USA	Retrospective population-based cohort, record linkage study	1,433 patients of all ages who sought any help from medical services for TBI (89% had mild TBI, 11% had moderate or severe TBI); mean age 28 years at injury;	6 months and 10 years	Mortality	Observed survival at 10 years after injury for 1303 patients with TBI who were alive at 6 months (93·1%) was not significantly different to expected survival (92·8%) based on population norms	Mortality increased with age, did not differ from population norms after survival to six months.
Dams-O’Connor et al (2013)48 Adult Changes in Thought study, Seattle, WA, USA	Prospective population-based cohort study	4,225 individuals without dementia, of whom 606 reported a lifetime history of TBI with loss of consciousness; aged ≥ 65 years at enrolment;.	0-to ≥ 40 years	Mortality, recurrent TBI, and dementia	Lifetime history of TBI was not associated with increased risk of mortality or dementia in individuals who were alive and did not have dementia at enrolment	A history of TBI was associated with elevated risk of further brain trauma during follow-up.

Abbreviations: SMR = standardized mortality ratio.

^*Interval between exposure to TBI and study observation; in the case of lifetime reported TBI in some studies, this follow-up period can comprise long intervals and some studies do not always report the exact range, because of uncertainty around the timing of the TBI.

^*Interval between exposure to TBI and study observation; in the case of lifetime reported TBI, this follow-up period can comprise long intervals and some studies do not always report the exact range, because of uncertainty around the timing of the TBI.