Does exogenous hormonal therapy affect the risk of glioma among females: A systematic review and meta-analysis.

Background: 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. Methods: Studies investigating the impact of exogenous female hormones on glioma risk were retrieved by searching 4 databases from inception until September 2022. Articles of any design, such as case-control and cohort studies, proving the relative risk (RR), odds ratio (OR), or hazard ratio were included. Summary OR values were calculated using a random effects model. Results: 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 = .00; OCP: OR = 0.80, 95% CI 0.67-0.96, P = .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 = .00; 5-10 years: OR = 0.80, 95% CI 0.66-0.97, P = .02; >10 years: OR = 0.69, 95% CI 0.54-0.88, P = .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 = .09; 1-5 years: OR = 0.88, 95% CI 0.72-1.02, P = .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 = .00). Conclusions: Our pooled results strongly suggest that sustained HRT and OCP use is associated with reduced risk of glioma development.