Does Exogenous Hormonal Therapy Affect the Risk of Glioma among Females: A Systematic Review and Meta-analysis

The effect of exogenous hormone replacement therapy (HRT) and oral contraceptive pills ( OCPs) on glioma risk in females is unclear despite numerous studies; hence, we conducted a meta-analysis to evaluate this relationship. Studies investigating the impact of exogenous female hormones on glioma risk were retrieved by searching four databases from inception until September 2022. Articles of any design, such as case–control and cohort studies, proving the relative risk (RR), odd ratio (OR), or hazard ratio were included. Summary OR values were calculated using a random effects model. Both HRT and OCP use of any duration decreased the risk of developing glioma [HRT OR = 0.78, 95%CI 0.66–0.91, p = 0.00; OCP: OR = 0.80, 95%CI 0.67–0.96, p = 0.02]. When stratified by duration of use, HRT use >1 year significantly reduced glioma risk (<1 year: OR = 0.82, 95%CI 0.63–1.07, p = 0.15; 1–5 years: OR = 0.79, 95%CI 0.67–0.92, p = 0.00; 5–10 years: OR = 0.80, 95%CI 0.66–0.97, p = 0.02; >10 years: OR = 0.69, 95%CI 0.54–0.88, p = 0.00). In contrast, only OCP use for >10 years significantly reduced glioma risk (<1 year: OR = 0.72, 95%CI 0.49–1.05, p = 0.09; 1–5 years: OR = 0.88, 95%CI 0.72–1.02, p = 0.09; 5–10 years: OR = 0.85, 95%CI 0.65–1.1, p = 0.21; >10 years: OR = 0.58, 95%CI 0.45–0.74, p = 0.00). Our pooled results strongly suggest that sustained HRT and OCP use is associated with reduced risk of glioma development.