Primary brain tumors following traumatic brain injury - a population-basedcohort study in Sweden

Objectives: The aim of this study was to explore the association between tr aumatic brain injury and brain tumor development. Methods: A cohort of patients hospitalized for traumatic brain injury durin g 1965-1994 was compiled using the Swedish Inpatient Register. Complete fol low-up through 1995 was attained through record linkage with the Swedish Ca ncer Register, the Cause of Death Register, and the Emigration Register. St andardized incidence ratios (SIRs), defined as the ratios of the observed t o the expected numbers of brain tumors, were used as the measure of relativ e risk. The expected number of brain tumors was calculated by multiplying t he observed person-time by age-, gender- and calendar year-specific inciden ce-rates derived from the general Swedish population. Results: The cohort included 311,006 patients contributing 3,225,317 person -years. A total of 281 cases of brain tumors were diagnosed during follow-u p. No associations were found between traumatic brain injury and the risk o f primary brain tumors, neither overall (SIR: 1.0; 95% confidence interval (CI): 0.9-1.2), nor in analyses broken down by main groups of brain tumors. Stratified analyses according to age at entry into the cohort, year of fol low-up, and severity of the brain injury all showed essentially the same nu ll results. Conclusion: No association between traumatic head injury and primary brain tumors has been found.