Table 1.

Summary of randomised controlled trials

Study	Objective	Country	Sample size	Attrition	ITT analysis	Oestrogen intervention	Statistical results	Conclusion
Kantarci et al (2016)7	Prevention of Alzheimer's disease only	USA	118	50 (42.4%)	No	0.45 mg/day CEE orally or 50 μg/day 17β-oestradiol transdermally for four years each	Transdermal groupa: odds ratio 0.04 [95% CI 0.004–0.44] Oral groupa: odds ratio 0.01 [95% CI 0.0006–0.23]	Transdermal 17β-oestradiol was associated with reduced beta-amyloid deposition in APOE ε4 carriers
Henderson et al (2000)10	Prevention and delaying onset of Alzheimer's disease	USA	42	6 (14.3%)	No	1.25 mg/day CEE orally for 16 weeks	Not applicable	No association between short-term oestrogen therapy and Alzheimer's disease
Shumaker et al (2003)11	Prevention of Alzheimer's disease only	USA	4532	0 (0%)	Yes	0.625 mg/day CEE orally	Relative risk 1.97 (odds ratio 1.99 [95% CI 1.17–3.38])	No association between short-term oestrogen therapy and Alzheimer's disease, but oestrogen plus progestin therapy increased risk of probable dementia
Shumaker et al (2004)22	Prevention of Alzheimer's disease only	USA	7479	0 (0%)	Yes	0.625 mg/day CEE orally	Relative risk 1.36b (odds ratio 1.39 [95% CI 1.01–1.91])	No association between oestrogen therapy and reducing risk of Alzheimer's disease. Increased risk of probable dementia in both oestrogen-only group and oestrogen plus progestin group

ITT, intention to treat; CEE, conjugated equine oestrogen; APOE, apolipoprotein E.

^a.Data to calculate relative risk was not available.

^b.Calculated based on the treatment group utilising oestrogen therapy only.