Assessing Premature Mortality Risk in TBI

We estimated the risk of premature death after having been diagnosed as having TBI with matched or sibling controls^{24 (link),35 (link)} using the clogit command in Stata statistical software, version 12 (StataCorp). The clogit command fits conditional (fixed-effects) logistic regression models to matched case-control groups. Traumatic brain injury patients and controls were followed up from the same time point (ie, from 6 months after TBI). We included 3 confounders (low income, single marital status, and immigrant status) on theoretical grounds based on related work on other neuropsychiatric disorders^{35 (link),36 (link)} and tested whether they were each associated (at P < .05) with caseness and outcome measures, respectively.^{37 (link)} Separately, we adjusted for emigration rates after TBI. In sensitivity analyses, we stratified by sex, psychiatric comorbidity (lifetime and separately for preexisting and new diagnoses), and co-occurring injuries at the time of TBI (Author Table 1). The STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines were followed (Author Table 2).