Traumatic brain injury, dry eye and comorbid pain diagnoses in US veterans

The purpose of the study is to evaluate the relationship between dry eye (DE) and pain diagnoses in US veterans with and without traumatic brain injury (TBI).

Retrospective cohort study of veterans who were seen in the Veterans Administration Hospital (VA) between 1 January 2010 and 31 December 2014. Veterans were separated into two groups by the presence or absence of an International Classification of Diseases, Ninth Revision diagnosis of TBI and assessed for DE and other comorbidities. A dendrogram was used to investigate the linkage between TBI, DE, chronic pain and other comorbid conditions.

Of the 3 265 894 veterans seen during the 5-year period, 3.97% carried a diagnosis of TBI. Veterans with TBI were more likely to have a diagnosis of DE compared with their counterparts without TBI (37.2% vs 29.1%, p<0.0005). The association was stronger between TBI and ocular pain (OR 3.08; 95% CI 3.03 to 3.13) compared with tear film dysfunction (OR 1.09; 95% CI 1.07 to 1.10). Those with TBI were also about twice as likely to have a diagnosis of chronic pain, headache, depression or post-traumatic stress disorder compared with their counterparts without TBI. Cluster analysis of TBI, DE and pain diagnoses of interest revealed that central pain syndrome, cluster headache, sicca syndrome, keratoconjunctivitis sicca and late effect of injury to the nervous system (as can be seen after TBI) were all closely clustered together.

DE and pain disorders occur at higher frequencies in patients with a diagnosis of TBI, suggesting a common underlying pathophysiology.