A recent review examined clinical and experimental literature for information on the long-term cognitive impact of traumatic brain injury (TBI) in the context of cognitive aging.

Neurobiological changes take place as part of the normal aging process. The issue evaluated through the literature is whether those individuals who experience cognitive problems as a result of TBI are at risk of accelerated and premature aging, and dementia.

In an elderly population with no history of TBI, the process of aging is associated with a decline in cognition. Cognitive weaknesses, including attention lapses and failures of working memory, are commonly experienced by people in their late 60s or early 70s. The literature suggests that younger individuals who experience a TBI may function on a cognitive level more often exhibited by much older individuals. Similarly, executive function weaknesses are also present in young adults after TBI.

The literature suggested that problems of cognition exhibited by young adults after TBI resemble cognitive weaknesses usually seen in elderly individuals who have had no neurological injury. The literature supports the argument that TBI can result in diminished cognitive reserve which may accelerate the normal process of cognitive decline, leading to premature aging and potentially increasing the risk of dementia.

Recovery from TBI typically involves gradual improvement of cognitive functions within the first weeks and months post- injury, followed by a slower rate of improvement. Improvement generally reaches a plateau around two years post-injury. This plateau is believed to last around 16 years. Some of the research suggests that cognitive decline may occur after TBI.

One conceptual approach to understanding cognitive decline in the elderly, which may aid in understanding accelerated cognitive aging after TBI, is based on the concept of “negative plasticity.” Negative plasticity incorporates the theory that social and environmental factors, rather than neurobiology, explain cognitive decline in older adults. These factors increase reliance on simplified cognitive processing at the expense of more complex processing (commonly referred to as negative learning), resulting in brain changes which then result in further cognitive disuse.

The theory of negative plasticity is linked to the concept of environmental enrichment (EE), which includes access to cognitive, physical, and social stimulation, and participation. Some of the literature suggests that EE can influence post-acute TBI decline. Various papers evaluating post-discharge experiences reveal that financial and social support, as well as home therapy, can have a positive impact on long-term outcome for individuals who experienced TBI. Other evidence suggests that a lack of EE, due to lack of resources or limited ability to engage in activities, may factor into post-acute cognitive decline.

More research is needed as to the benefits of EE in brain-injured individuals. The review provides support for providing a stimulating environment for individuals who have suffered TBI. Maximizing EE in the post-acute stages of TBI may improve long-term outcomes.