Prevalence trends for indices of subjective well-being showed varying patterns of age and outcomes. Figure 6 shows the trend of dissatisfaction with life (as indicated by a score <21 on the Satisfaction With Life Scale17) 5 years postinjury, in which those aged 40 to 49 years were most likely to be dissatisfied (48.6%) with rates falling as age either increased (8.1% for those 80 years and older) or decreased (28.4% for those aged 16-19 years). Moderate or severe depressed mood on the Patient Health Questionnaire18 at 5 years showed a similar pattern, with those aged 40 to 49 years having the highest prevalence of depressed mood (15.4%). Rates for depressed mood were lower as age increased and decreased from 40-49 years. For alcohol misuse, a markedly different relation with age was observed, with patients aged 16 to 19 years and 20 to 29 years having the highest prevalence rates (36.8% and 37.7%, respectively) and decreasing rates as age increased. Illicit drug use 5 years postinjury showed a similar pattern, although a lower rate. Those aged 16 to 19 years at injury were most likely to use illicit drugs (31.3%), with prevalence decreasing as age increased.
Five years postinjury, 57% of the population was classified as moderately disabled or worse on the Glasgow Outcome Scale–Extended.19 Those aged 40 to 49 years at injury had the highest rate (67.1%), with rates declining as age at injury decreased or increased until 80 years and older when poor global outcome increased. Deterioration was operationalized as anyone whose 5-year Glasgow Outcome Scale–Extended score was at least 1 category lower than their status on the same measure 1 or 2 years postinjury. Overall, 39.1% declined from an earlier attained level, with a relatively consistent rate across all age groups (see Figure 7).
The purpose of this study was to estimate selected health and social outcomes for adults in the United States who are 5 years post-TBI requiring rehabilitation. These estimates have not been possible previously because population data, themselves only available since 2001, have been limited to a relatively small set of descriptors collected at the time of rehabilitation. The ability to weight the TBIMS-NDB so it reflects the US population is a new development that provides unique insight into the public health burden of these injuries.
The findings reported here raise concerns about both mortality and morbidity 5 years post-TBI. Approximately 1 in 5 of those who received rehabilitation (1 in 4 of the known outcomes) had expired by 5 years postinjury. There was a marked age effect for death, as might be expected, and while we did not compare the mortality rate to age-matched controls, other studies of deaths among the TBIMS-NDB cohort have found that all age groups except the very oldest—those 80 years and older—had standardized mortality rates exceeding those expected in the general population.20,21 Identifying factors beyond age that predispose these patients to premature mortality remains a pressing public health concern.
For those alive 5 years postinjury, the current findings indicate that there is a marked interaction between age at injury and prevalence of undesirable health outcomes, particularly institutionalization and, to a lesser degree, rehospitalization. Measures of functional independence (eg, the FIM Motor, FIM Cognitive, and need for supervision) were associated with increasing age, as were the ability to drive and return to work. Even though older persons experienced the worst outcomes, for some variables, the rates occurring for younger age groups were still relatively high (eg, rehospitalization, FIM Cognitive, driving, and return to work). This high burden of injury translates into significant societal costs due to the length of time for which lost earnings and lost opportunity costs accrue.
The relatively higher rates of diminished health and functional dependence among older age groups are also observed in the general population; the extent to which prevalence among those who received TBI rehabilitation exceeded normal aging was beyond the scope of this study. At a minimum, for those age-related outcomes that showed high rates among younger age groups, there is a substantial likelihood that negative consequences exceeded general population rates. Whether or not unfavorable outcomes exceed population rates, high prevalence still suggests a public health burden.
Not all negative consequences reflected an interaction between older age and poorer outcome. Poorer subjective states, specifically life dissatisfaction and depression, were most common among those in the middle age groups (30-59 years), followed by those younger at injury. Older age groups had higher rates of positive subjective states as age at injury increased. Alcohol misuse and illicit drug use were most common in the youngest age at injury groups. The observation that younger people were more likely to misuse substances is consistent with prevalence in the general population, although the rate is lower than that for same-aged peers.22
It is interesting that those aged 30 to 59 years at injury experience the greatest life dissatisfaction and depression when persons older at injury have the worst outcomes for health status and functional independence. The middle age groups also showed the highest prevalence of poor global outcome, matched only by those 80 years and older at injury. This concurrence may not only explain the greater dissatisfaction but also raises the question why worse global outcome did not mimic the linear relation between increasing age and prevalence of poorer outcomes. This discrepancy between global outcome and both health status and functional dependence may suggest that there are multiple influences predisposing these individuals to negative consequences. Perhaps, cognitive and social consequences are more limiting for those aged 30 to 59 years at injury than for the younger age groups. In older age groups, the social support provided by marriage, adult children and long-established social networks may serve as a protective factor from negative psychosocial outcomes.
Also inconsistent with the relations observed between age at injury and prevalence of negative consequences was the lack of relation between age and the occurrence of deterioration from a previously attained global outcome. An earlier report of 10-year outcomes for the TBIMS cohort noted that older age at injury was associated with greater likelihood of deterioration.23 In the current study, deterioration was for the most part equally distributed across age at injury groups. Determining whether causes of deterioration are also equally distributed, or whether different age groups deteriorate for different reasons, was beyond the scope of the current study and will await further investigation. However, there are multiple potential sources of deterioration that could contribute to poorer outcomes, including:
- TBI triggers a progressive, degenerative process (ie, Parkinson disease, Alzheimer disease, chronic traumatic encephalopathy);
- frontal lobe damage endemic to TBI causes changes in self-regulation, which lead to death and disability from risky behaviors;
- TBI causes loss of functional independence, which interacts with aging, either normal aging or other chronic medical conditions, to increase poor health; and/or
- TBI exacerbates social factors (eg, lack of social support or environmental stressors), including health disparities (eg, lack of resources for additional rehabilitation or poor access to follow-up healthcare) to result in poorer health.
The 2012 Galveston Brain Injury Conference focused on long-term consequences and arrived at the following consensus statement:
Injury to the brain can evolve into a lifelong health condition termed chronic brain injury (CBI). CBI impairs the brain and other organ systems and may persist or progress over an individual's life span. CBI must be identified and proactively managed as a lifelong condition to improve health, independent function and participation in society.24(p6)
The current study underscores the concerns expressed in this statement by demonstrating that at least among those requiring rehabilitation for TBI, both premature death and deterioration may occur as early as 5 years postinjury. These findings point to the need for further research to identify causes for deterioration so that preventive strategies can be proposed and tested.
There are several potential limitations to this study, although foremost is the caution necessary when population estimates are derived from weighting cohort data. For instance, while the TBIMS-NDB data were weighted to reflect demographic characteristics and indices of functional severity (ie, admission FIM Motor and FIM Cognitive, rehabilitation length of stay), injury severity characteristics were not available for weighting. It is possible that older adults enter rehabilitation for TBI due to consequences that are an interactive function of both the brain injury severity and other comorbid conditions. The broader US population of older adults in rehabilitation for TBI may have a different “mix” of brain injury versus other etiologies contributing to their need for rehabilitation than those older adults included in the TBIMS NDB, which could result in different estimates of 5-year outcomes. In addition, the rates reported were among those living; thus, the estimates of the prevalence of negative consequences are attenuated because of “survivor bias.” Given that a large proportion of those who incurred a TBI expired by the 5-year follow-up interview and that weighting was recalculated to exclude known cases of expiration, the negative effects of time post-TBI may well be underestimated. The cohort used to calculate the outcome analyses could have some inherent characteristic that enhanced their chance of survival, and as such the estimates presented here would be inflated by this form of selection bias.25 As such, these estimates should be applied cautiously and within the appropriate context.
The current findings suggest that significant mortality and morbidity occur by 5 years post-TBI in patients who have received rehabilitation. Poorer medical, functional, and participation outcomes were associated with, but not limited to, older age. Other age groups had poorer mental and emotional outcomes, including life dissatisfaction. Both the high rate of premature mortality and the deterioration observed for global outcome may suggest that there are multiple influences affecting poorer health and function, underscoring the need for proactive interventions to be available after the acute phase of recovery.
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Keywords:© 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins
craniocerebral trauma; epidemiology; outcomes; prevalence; rehabilitation; traumatic brain injury