Reproductive factors and exogenous hormone use and risk of adult glioma in women in the NIH-AARP Diet and Health Study.

Experimental evidence suggests that estrogen and other steroid hormones may protect against glioma. Although epidemiologic studies provide only weak support for a role of exogenous or endogenous hormones in gliogenesis, few cohort studies have addressed this question. The authors, therefore, examined the association between menstrual and reproductive factors, exogenous hormone use, and glioma risk among 225,355 women aged 50-71 years who completed the baseline questionnaire in the NIH-AARP Diet and Health Study. During 7.5 years of follow-up, 174 cases of incident, primary glioma were ascertained. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI) for exposures, taking potential confounders into account. Older age at menarche was positively associated with risk: HR 1.67 (95% CI: 1.03, 2.69). Other reproductive factors, including age at first live birth, parity, age at menopause, type of menopause (natural vs. medical) and exogenous hormone use showed no association with glioma risk. The results were similar when the analysis was restricted to cases with glioblastoma (N = 130). The present study provides only limited support for the hypothesis that menstrual/reproductive factors or exogenous hormone use play a role in gliogenesis.