The Societal Impact of Traumatic Brain Injury on Employment and Income: A National Observational Cohort Study of 18,157 Patients

Introduction: Traumatic brain injury (TBI) can detrimentally impact cognition and physical health, contributing to resultant workplace absenteeism. Despite the importance of this outcome domain for affected patients, the societal impacts of traumatic brain injury (TBI) on post-injury personal income and employment are not known. We sought to quantify the magnitude of attributable lost work earnings and employment using income tax data sources that were linked to health administrative data.

Methods: We performed a national retrospective observational cohort study including tax-filing survivors of TBI ages 19-61 years injured between 2007-2017. We sampled uninjured comparator individuals from our cohort using coarsened exact matching on sociodemographic and injury characteristics. Linear and logistic mixed effects difference-in-difference (DID) regressions were used to estimate the annualized magnitude of personal income loss and proportion displaced from employment during each of the 3 years following injury respectively (Y+1, Y+2, Y+3). This analysis was repeated within mild, moderate and severe TBI subgroups. We performed sensitivity analyses restricting our cohort to only employed individuals prior to injury and to individuals aged 30-55 years to mitigate effects of early retirement.

Results: We identified 18,157 patients with TBI, of which 83% were employed at time of injury. Mean income was $46,000 prior to injury. The average loss of personal annual income was -$7,700 dollars (CDN) in Y+1 and -$5,300 in Y+3. Approximately 8.2% of individuals were unemployed in Y+3. The magnitude of personal income loss for mild, moderate and severe TBI subgroups was -$3500, -$8000, and -$22,700 respectively at Y+3. Similarly, the proportion of unemployed individuals associated with TBI was 5.6%, 12%, and 20% across the same groups at Y+3 following injury. Our findings were robust to influences of pre-injury employment status and effects of early retirement.

Conclusion : This work represents the first national cohort data quantifying the personal income loss and workplace absenteeism associated with TBI. These findings may be used to inform post-injury care pathways, social services, resource allocation and shed light on post-injury disparities in healthcare.