the brain-cancer diagnosis. ORs for glioma or meningioma were not significantly increased in men who had had any TBI 5 years or more before diagnosis (OR, 1.18; 95% CI, 0.94–1.48 and OR, 1.49; 95% CI, 0.86–2.57, respectively) or who had had a severe TBI 5 years or more before (OR, 1.13; 95% CI, 0.87–1.48 and OR, 1.15; 95% CI, 0.57–2.34, respectively). There was no significant increase in the risk of either brain tumor in women regardless of TBI severity. Men had a slightly increased OR for glioma if they had sustained more than one TBI 5 years or more before (OR, 1.52; 95% CI, 1.00–2.32), but not if they had more than one TBI regardless of timing (OR, 1.67; 95% CI, 0.56–4.98). In men who had sustained their TBI 15–24 years before diagnosis, there was a statistically significant increase in the risk of meningioma (OR, 5.35; 95% CI, 1.72–16.62), but the increase was not seen in connection with other latent periods or in women.


In a study of primary brain tumors in residents of the Rein-Neckar-Odenwald area of Germany, Schlehofer et al. (1992) identified 226 cases diagnosed in two neurosurgical hospitals in January 1987–December 1988, of which 115 were histologically confirmed gliomas, 81 were meningiomas, and 30 were acoustic neuromas. The 99 men and 127 women, 25–75 years old, were interviewed during their hospital stay, as were 418 age- and sex-matched controls from the same residential areas as the cases. TBI that had occurred more than 5 years before and required a visit to a doctor were reported by 46 (20%) of the subjects and 113 (27%) of the controls (OR, 0.71; 95% CI, 0.5–1.1 for any brain tumor; OR, 0.70; 95% CI, 0.4–1.2 for gliomas; and OR, 0.52; 95% CI, 0.3–1.0 for meningiomas, adjusted for age and sex). The authors reported that there was no effect of having multiple TBIs or of varied latent periods, but the data to support these statements are not provided.


These 11 studies had mixed results. Eight found evidence of associations between history of TBI and later brain tumors, and four did not. The results of the four Preston-Martin studies suggest that the odds of meningioma are increased in people who have had a TBI, especially those with relatively remote histories (15 years or more before). That was also found by Phillips et al. and in a study with more heterogeneous histologic subtypes by Monteiro. Nonetheless, the findings of those studies are less compelling than the findings of the large population-based studies in Minnesota, Denmark, and Sweden primarily because of the potential for overascertainment of exposure among cases due to self-reporting of TBI. Nonetheless, it is notable that some well-conducted studies yielded a relatively specific association between TBI and risk of later meningioma as opposed to other tumor types and that some studies yielded a finding of a latent period of 10 years of more.

SECONDARY STUDIES

The committee identified two secondary studies that evaluated the relationship between TBI and brain tumors (Choi et al., 1970; Zampieri et al., 1994).


In a retrospective study (Choi et al., 1970) of patients with brain tumors in four University of Minnesota–affiliated hospitals in Hennepin County, Minnesota, there were 126 cases of histologically verified tumors diagnosed in 1963–1964. TBI was defined as a fractured skull, unconsciousness, or bleeding from the head that led to hospitalization or surgery. Controls were admitted to the hospitals for any condition other than tumors and were excluded if they had any neurologic, psychiatric, ophthalmologic, or lymphatic disorder; they were matched to cases by hospital of admission, sex, age, race, geographic area of residence, and locale of residence.



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