| This dissertation presents three related investigations that evaluate the previously reported association between loud noise exposure and the risk of acoustic neuromas, as well as the proposed biological basis for the association. The goal of the first investigation was to examine further the role of loud noise in acoustic neuroma etiology. In a population-based case-control study conducted from 1999-2002 in Sweden, reports of occupational and nonoccupational loud noise exposure of 146 acoustic neuroma cases and 564 controls were compared. Individuals reporting loud noise exposure from any source were found to be at increased risk for acoustic neuromas. The findings of an increased risk of acoustic neuromas with loud noise exposure support previous research.;The goal of the second investigation was to further examine the association between noise exposure and acoustic neuroma using an objective measure of exposure. A total of 793 acoustic neuroma cases were identified between 1987 and 1999 from the Swedish Cancer Registry, to which 101,756 controls were frequency matched. Occupational information, available for 599 of the cases and 73,432 of the controls, was obtained from censuses and linked to a job exposure matrix. Of three studies of noise exposure and acoustic neuroma risk to date, this is the first to use a job exposure matrix to assess exposure. Contrary to previous study results the findings do not demonstrate an increased acoustic neuroma risk related to occupational noise exposure.;A mechanism of acoustic neuroma tumorigenesis during the cellular repair process following acoustic trauma has been proposed, whereby cellular division results in DNA replication errors which may in turn lead to chromosomal changes essential for neoplastic transformation. In the third investigation, an extensive literature search was conducted to evaluate the biological plausibility of this hypothesis. The tumor typically involves the vestibular rather than the acoustic division of the eighth nerve, however intralabyrinthine and cochlear nerve schwannomas have been reported. Additionally, evidence of vestibular damage in rodents has been demonstrated following acoustic trauma. The proposed hypothesis is therefore plausible, however further research is needed to elucidate the precise biological basis for the association between loud noise and acoustic neuromas. |
