Chronic Conditions and Traumatic Brain Injury

By Raj G. Kumar, PhD MPH, Assistant Professor, Icahn School of Medicine at Mount Sinai

The conceptualization of traumatic brain injury (TBI) as a chronic condition is no longer a new concept in the field. The idea, originating from Masel and Dewitt’s seminal 2010 Journal of Neurotrauma article, suggests that unlike injuries to other parts of the body such as a broken arm, TBI should be recognized as a disease process due to the uniquely intricate nature of damage to the brain, the body’s most complex organ. In the subsequent years, there has been an advancement in science to characterize the labyrinth of medical complexity experienced by individuals living with TBI.

Research from the TBI Models Systems National Database has provided some key insights on prevalent and incident medical comorbidities with TBI. In a 2018 epidemiological study, it was found that patients over the age of 50 acutely hospitalized with TBI were diagnosed with three “clusters” of medical conditions. The first, and most common, were pre-existing chronic diseases, including hypertension, diabetes, coronary heart disease, and lipid disorders (i.e., hypothyroidism). The next most common were infections and complications, presumably co-occurring with the TBI during the acute hospitalization, including pneumonia, fluid and electrolyte imbalances, nutritional deficiencies, and other parasitic and bacterial infections. The third cluster was substance abuse or dependence and transient mental disorders (i.e., delirium). Nearly all (~92%) of patients with TBI had some pre-existing or co-morbid condition in one of these three cluster categories during their acute hospitalization. This striking finding illustrates that persons with TBI are dealing with tremendous medical complexity – spanning from multi-system chronic disease, acute infection, and substance use – in the early phases of recovery that extend beyond the primary consequences of brain trauma. In a follow-up study, it was determined that greater disease burden spanning these three comorbid clusters was associated with longer lengths of inpatient stays and greater likelihood of rehospitalization after inpatient discharge.

Research has indicated that presence of certain comorbidities, more than others, could interact with acute and post-acute TBI recovery. One study using medical claims data evaluated 39 different comorbidities present at admission to inpatient rehabilitation and found that 12 were most predictive of the extent of functional impairment at the point of discharge from rehabilitation. These select conditions included, among others, swallowing disorders, seizures, congestive heart failure, fluid and electrolyte imbalances, pneumonia, renal disease, weight loss, diabetes, and weight loss. Interestingly, this list is a mixture of conditions likely caused by the TBI itself, and others, like congestive heart failure and renal disease, that were likely present pre-injury, but still meaningfully impacted recovery from TBI compared to similar persons without these conditions.

Subsequent to the acute inpatient phase following TBI, there is interest to understand what characteristics may increase an individual’s likelihood to become re-hospitalized after returning to the community. Indeed, the Centers for Medicare and Medicaid (CMS) prioritizes rehospitalization as a quality of care metric that impacts reimbursement. Data indicates that re-hospitalization after TBI can be grouped into two categories: planned and unplanned hospitalization. The former, planned hospitalization, is especially common for patients who undergo a craniectomy procedure to manage high acute intracranial pressure that requires follow-up in the months following injury to reinsert the skull plate. Other individuals may experience an unplanned hospitalization after reintegrating into the community. These types of hospitalizations are particularly of interest as they could in some instances be preventable with prophylactic measures. For example, data indicates that by far the most common reason for rehospitalization in the first 5 years post-injury is seizure disorder. Anti-seizure prophylactic medications are crucial for patients with TBI to take as prescribed by their treating physician to prevent recurrent seizure episodes that could escalate to a hospitalization or death.

Furthermore, beyond the acute and sub-acute periods after injury, there is a tremendous interest in the field to understand the long-term consequences of TBI on risk for age-related cognitive diseases, including Alzheimer’s disease and related dementias. The press surrounding the relationship between exposure to repetitive head impacts and risk for chronic traumatic encephalopathy (CTE) has heralded most of the attention in this area. However, the relationship between a single moderate-to-severe TBI and risk for later life dementia remains an open question with mixed findings in the literature to date. The evidence in this area will surely be built in the subsequent years with better life course epidemiological cohort studies with more detailed TBI and dementia characterization than has been present with extant data sources. Beyond the association between TBI and dementia, research is also pushing toward better understanding the mechanisms underlying this relationship to guide disease-modifying treatments.

It is indeed an exciting time in the TBI field. We are fortunate to have a growing number of invested stakeholders, including young new clinicians, researchers, and advocates, who have brought new perspectives and energy to move the field forward. Simply, we are expanding beyond stating the vacant axiom “TBI is a chronic disease”, to having empirical data to illustrate what that actually means for persons living with TBI and their loved ones.