Female sex hormones are thought to affect women's risk of developing central 
nervous system (CNS) tumors. Some have reported an increased risk in users of 
menopausal hormone therapy (HT) but evidence is limited. In the UK General 
Practice Research Database we compared prospectively collected information on HT 
prescriptions in women aged 50-79 years with CNS tumors diagnosed in 1987-2011 
with that in matched controls (four per case). Relative risks (RRs) in relation 
to prescribed HT were calculated overall and by CNS tumor subtype. Statistical 
tests are two-sided. For all CNS tumors (n = 3,500), glioma (n = 689), 
meningioma (n = 1,197), acoustic neuroma (n = 439), and pituitary tumors (n = 
273) adjusted RRs for women prescribed HT versus not were, respectively, 1.21 
(95% confidence intervals (CI) = 1.10-1.32, p < 0.0001), 1.14 (0.93-1.40, p = 
0.2), 1.30 (1.11-1.51, p = 0.001), 1.37 (1.06-1.75, p = 0.01), and 1.35 
(0.99-1.85, p = 0.06). There was no significant difference in risk by tumor 
subtype (p(heterogeneity) = 0.6). A meta-analysis was conducted, combining our 
results with those from other published studies with prospectively collected 
exposure information. The meta-analyses yielded significantly increased risks 
for all CNS tumors, glioma and meningioma in users of estrogen-only [1.35 
(1.22-1.49), 1.23 (1.06-1.42) and 1.31 (1.20-1.43), respectively] but not 
estrogen-progestin HT [1.09 (0.99-1.19), 0.92 (0.78-1.08) and 1.05 (0.95-1.16), 
respectively]; these differences were statistically significant (p < 0.005 for 
each tumor type). There was no significant difference between glioma and 
meningioma risk in users of estrogen-only HT. The totality of the available 
evidence suggests an increased risk of all CNS tumors (and of glioma and 
meningioma separately) in users of estrogen-only HT. Absolute excess risk (2 per 
10,000 users over 5 years) is small.