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Primary brain tumors following traumatic brain injury--a population-based cohort study in Sweden
1Department of Rehabilitation Medicine, Karolinska Institute, Danderyd Hospital, Stockholm, Sweden. catharina.nygren@mbox304.swipnet.se
Objectives:
The aim of this study was to explore the association between traumatic brain injury and brain tumor development.
Methods:
A cohort of patients hospitalized for traumatic brain injury during 1965-1994 was compiled using the Swedish Inpatient Register. Complete follow-up through 1995 was attained through record linkage with the Swedish Cancer Register, the Cause of Death Register, and the Emigration Register. Standardized incidence ratios (SIRs), defined as the ratios of the observed to the expected numbers of brain tumors, were used as the measure of relative risk. The expected number of brain tumors was calculated by multiplying the observed person-time by age-, gender- and calendar year-specific incidence-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-up. No associations were found between traumatic brain injury and the risk of 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 follow-up, and severity of the brain injury all showed essentially the same null results.
Conclusion:
No association between traumatic head injury and primary brain tumors has been found.