Cognitive-physical-functional correlates in chronic brain injury: a pilot study

Acquired brain injury, traumatic or non-traumatic, is a leading cause of disability in the United States [1]. Two common forms of acquired brain injury, with significant long-term sequlae, are traumatic brain injury and stroke. Nearly a third of adults with stroke have lifelong disability. Similarly, traumatic brain injury (TBI), especially moderate to severe TBI, can result in various cognitive, physical, and functional disabilities [2]. Rehabilitation programs have proven beneficial in mitigating some of the short-term and long-term sequelae following brain injuries [3].

Despite making significant gains in the initial stages of recovery (e.g. six-month post-TBI), long-term outcomes, especially in areas of home and community integration are limited [4], and can entail residual cognitive, psychological, and physical impairments [5]. Therefore, researchers and clinicians are beginning to recognize the benefits of integrative approaches to mitigate chronic long-term functional outcomes. Integrative approaches combine multiple rehabilitation strategies and/or techniques to accomplish the desired outcomes. For example, rehabilitation programs may integrate physical exercises (e.g. aqua therapy) to improve daily functionality. These integrative approaches have demonstrated gains in both preservation (in healthy adults) and enhancement (in adults with brain injuries) of cognitive and psychological function [6,7,8].

In recent years, researchers have begun to explore the relationships between these cognitive, physical, and functional domains. A recent study found positive correlations between cognitive performance (attention and verbal fluency measures) and physical performance (motor speed and balance) [9]. Adults with TBI, despite being considered well-recovered, reported physical problems such as difficulty running, clumsiness in arm movements, and fatigue [10,11]. More research is needed to understand the correlation between cognitive, physical abilities and daily functionality. Therefore, the current pilot study examined the correlation between cognitive, physical, and daily functionality in adults with brain injury, including TBI and Stroke. It is anticipated that this preliminary study would lay the grounds for a more extensive multidisciplinary (e.g., Occupational, Speech, and Physical Therapy) project aimed at studying integrative therapies to improve clinical outcomes in brain injury rehabilitation.

The study group comprised 17 participants (11 males and six female). Eight participants were stroke survivors and nine had a history of a TBI. Scores on all three domains (i.e., cognitive, physical and functional measures) were obtained for 11 participants. Spearman's nonparametric correlational analyses were used to examine the relationships between cognitive, physical and daily life (functional) domains. Participant demographics are detailed in Table 2.

Raw scores on all measures are detailed in Table 3.

Significant correlations between the three domains were identified (Tab. 4).

Higher scores on CBMS correlated with (a) higher visual-auditory learning (r = 0.900, p = 0.037), and inversely with (b) scores on pair cancellation (interference capacity) (r = −0.900, p = 0.037). With regard to correlations between the functional and physical domains, scores on BBS correlated significantly with SWLS scores (r = 0.671, p = 0.048).

CIQ productivity was significantly associated with high concept formation, and this relationship was strong (r = 0.676, p = 0.032). No significant relationships were found between other CIQ subscales and the cognitive domain, possibly due to the small sample size. However, when looking at the effect size, better CIQ productivity appears to be moderately related to higher story recall (r = 0.588) and better retrieval fluency (r = 0.531). Surprisingly, higher CIQ home integration was moderately correlated with lower visual auditory learning (r = −0.489), and higher CIQ social integration was moderately correlated with lower concept formation (r = −0.525) and retrieval fluency (r = −0.462).

To further confirm whether the relationships between physical and functional performances differed by injury type, the subsamples were subjected to Spearman's rho nonparametric correlation analyses. As shown in Table 5, no significant relationship was found in either injury group, partly due to the small sample size.

Therefore, the effect size (r coefficient) was used to assess the magnitude of the relationships. In the stroke group, higher scores on BBS were strongly related to better self-care scores on BI (r = 0.789), but this relationship was not found in the TBI patients. A positive relationship between BBS and SWLS was found in both the stroke (r = 0.564) and the TBI group (r = 0.738). This result was consistent with the result for the overall sample described in the previous section.

Participation and engagement in life tasks in a complex interrelated phenomena between multiple domains. The present study found a positive relationship between cognitive, physical and functional domains in adults with brain injury. These findings support prior evidence that one domain exerts an influence on another [9]. In recent years, several studies have examined the benefits of combining/integrating multiple rehabilitation therapies to optimize outcomes. For example, in a Virtual Reality based feasibility trial, researchers found that combining arm reaching with attention and memory training yielded gains in chronic stroke survivors [22]. Similarly, positive effects on emotional, motor, and cognitive aspects were demonstrated in adults with multiple sclerosis with integrated cognitive and neuromotor training [23]. Clinically, the current findings emphasize the potential benefits of integrating/combining multiple domains during therapy sessions. It is intuitive to rehabilitation professions that all three domains play a role in daily function. While each domain is unique, each one supports, and could potentially enhance, another. As seen in the current study, this interplay between domains can be exploited by rehabilitation professionals.

Physical/motor activities could be integrated as preparatory activities for performing a functional task, such as completing balance exercises before attempting self-care interventions. A short jog or stretching could be a warm-up prior to starting cooking tasks in the kitchen. Similarly, these physical exercises could serve as a warm-up prior to a initiating a cognitively challenging task, such as preparing for a class or a lecture. All three domains are important for long-term outcomes including home and community integration.

Case example: Consider a 50-year-old, Mr. J, who sustained a moderate TBI three years previously. Prior to his injury, Mr. J worked full time as a food service business owner, was a gym enthusiast, and actively involved in social and community activities. Mr. J received acute inpatient and outpatient therapy services and was able to return to his food service business at part time capacity with the help of his family members. Yet, Mr. J has significantly reduced his participation in home management tasks and social activities. He also reports increased fatigue after work and occasional forgetfulness and feeling stuck when it comes to generating ideas for his food service business. He was recently referred to occupational, physical, and speech therapy to improve his participation, fatigue, and cognitive abilities. An integrative therapy plan could start with 10– 15 minutes of jogging or stationary bike (given Mr. J is a gym enthusiast) as a warm up, followed by helping his wife in laundry and house cleaning. Similarly, planning a meeting with a friend for coffee could be followed by working with work colleagues to plan a new recipe or item for his food business. Exploring options to be a part-time volunteer at his local library or place of worship could improve social engagement and manage his fatigue. Taking neighborhood walks with his family members during the weekend could be added to the therapy home program. By tailoring Mr. J's therapy sessions to engage cognitive, physical, and functional domains, the therapy could likely increase his participation, independence, cognition, and overall satisfaction with life.

There are at least five limitations of the study that need to be considered for further research. Firstly, the samples in both the Stroke and TBI groups were rather small; larger sample sizes are needed to help generalize the findings. Secondly, while documenting initial injury severity is critical to accurately establish the relation between initial injury severity, recovery, and current level of functioning, the participants were recruited primarily from the community at periods years after brain injury. Third, it is likely that coexisting or preexisting medical conditions (e.g. COPD) or current living situations, may have contributed to variations in performance across groups. Fourth, the current study examined daily functionality on self-rated questionnaires; these are restricted to the self-perception of function, which may be inaccurate. A more accurate characterization of daily function would be provided by an assessment of real-life task performance. Fifth, the current study included wide age ranges, including age at testing and age at injury (3–40 years). We propose that future studies should more rigorously specify initial injury severity to confirm the current findings; for example, the relationship between cognitive and physical domains in mild TBI/mild Stroke may be different from those in moderate TBI/moderate stroke. Research has demonstrated that frontal network myelination continues into the early third decade of life (i.e., into the early twenties), and an injury at a young age disrupts the maturation of frontal functions that affect functional outcomes [24]. Future studies could examine the effect of age at injury while examining cognitive function, either as an outcome measure or a treatment factor.

Rehabilitation professionals, such as occupational, physical, and speech therapists, are always looking for efficient ways to improve outcomes. Clients may prefer engaging in activities that draw upon one domain (e.g., physical exercises) even if the focus of the rehabilitation therapy session is on another (e.g., cognition). Exploiting the interplay between cognitive, physical, and daily function domains could be one way to improve rehabilitation outcomes.