Reproductive factors and hormone use and risk of adult gliomas

Previous research suggests there may be a hormonal influence on glioma risk as evidenced by lower rates in females, change in incidence rates around ages at menarche and menopause, and presence of hormone receptors in glial tumors. Using the large San Francisco Bay Area Adult Glioma Study, we investigated whether reported reproductive factors and hormone use were associated with gliomas overall or with histologic subtypes among female cases (n = 619) and controls (n = 650). We found that reproductive factors were generally not associated with gliomas. Weak to moderately elevated odds ratios were observed for self-reported later age at menarche (14+ vs. 12-13 years old: adjusted odds ratio (AOR) = 1.39, 95% confidence interval (CI): 1.02-1.89), particularly for non-glioblastoma histologies (AOR = 1.64, 95% CI: 1.11-2.43). Inverse associations were observed for ever self-reported use of exogenous hormones (oral contraceptive use: AOR = 0.72, 95% CI: 0.53-0.99; postmenopausal hormone use: AOR = 0.56, CI: 0.37-0.84). However, cumulative hormone exposure defined multiple ways demonstrated no clear pattern of association. The results of this study suggest that any protective effect of hormones on gliomas may be limited to exogenous hormones, but a more detailed history of exogenous hormone use is needed to confirm findings.