0150 Is a possible relationship between occupational noise exposure and vestibular schwannoma (acoustic neuroma) causal or due to bias? a systematic review and meta-analysis

Objectives Vestibular schwannoma (acoustic neuroma) is a benign, slow-growing tumour, arising from the nerve sheath of the vestibular branch of the eighth cranial nerve. Some studies show a possible relationship between noise exposure and schwannoma, while others not. Our objective was to assess possible associations between occupational noise exposure and schwannoma. Methods We performed a systematic critical literature review of original articles from key literature databases of associations between workplace noise and health, completed in January 2017. For the meta-analysis, we selected studies of sufficient quality with a measure of association between occupational noise exposure and schwannoma. Results Six studies were selected, all matched case-control studies, with a total of 1487 cases, five population-based and one registry study. Five studies had self-reported exposure information from interview (4) or questionnaire (1), and three had data from job-exposure-matrices (JEMs). Two studies had both self-report and JEM information. Self-reported occupational noise exposure was consistently associated with schwannoma, odds ratio (OR) 1.70 (95% CI 1.32–2.18). JEM results gave OR 1.16 (0.75–1.81), with more heterogeneity between studies. Long noise exposure (≥15/18 years; 2 self-report, 2 JEM studies) was also consistently associated with schwannoma, OR 1.76 (1.04–2.99). Conclusions The results indicate that noise exposure might be associated with schwannoma. We found strong and consistent associations for self-reported noise exposures and exposures of longer duration. JEM-based associations were weaker, maybe due to non-differential misclassification. However, reasons other than a causal relationship, such as recall bias, detection bias or publication bias, cannot be excluded.