Here is the design of a clinical trial:

Official Title: Efficacy and Safety of Ferrous Iron on the Prevention of Vascular Cognitive Impairment Among Patients With Cerebral Infarction/TIA,FAVORITE

Included conditions:
- Vascular Cognitive Impairment
- Dementia, Vascular
- Iron-deficiency
- Cerebral Infarction
- TIA

Study Armgroups:
- {'label': 'Ferrous succinate', 'type': 'ACTIVE_COMPARATOR', 'description': 'Ferrous succinate sustained-release tablets（Ferrous succinate 0.2g）1 tablet, Qd, po during or after breakfast, Lasting for 12 weeks.', 'interventionNames': ['Drug: Ferrous succinate']}
- {'label': 'placebo', 'type': 'PLACEBO_COMPARATOR', 'description': 'placebo with almost the same size, color and smell as Ferrous iron will be used with 1 tablet, Qd, po during or after breakfast, Lasting for 12 weeks.', 'interventionNames': ['Drug: Ferrous succinate']}

Interventions:
- {'type': 'DRUG', 'name': 'Ferrous succinate', 'description': 'Ferrous succinate sustained-release tablets（Ferrous succinate 0.2g）1 tablet, Qd,po during or after breakfast, Lasting for 12 weeks.\n\nplacebo with almost the same size, color and smell as Ferrous iron will be used with 1 tablet, Qd, po during or after breakfast, Lasting for 12 weeks.', 'armGroupLabels': ['Ferrous succinate', 'placebo'], 'otherNames': ['Placebo']}

Primary Outcomes:
- {'measure': 'prevalence of vascular cognitive impairment in patients given Ferrous succinate versus placebo', 'description': 'Vascular cognitive impairment will be diagnosed with Montreal Cognitive Assessment(MoCA, range 0-30 scores) \\<26 scores', 'timeFrame': '1 year after randomization'}

Please estimate the sample size based on the assumption: 
A significance level of 0.05 for a two-sided test, statistical power of 90%, and an estimated 20% of patients with mild anaemia or low haemoglobin.
Sample size
        The sample size calculation is based on the risk of primary outcome (3-month risk of VCI). We applied the following assumptions: a significance level of 0.05 for a two-sided test; statistical power of 90%; according to the previous studies, the risk of VCI within 3 months after ischaemic cerebrovascular disease is 21%â70%, it is conservatively estimated that the risk of VCI within 3 months in patients with ischaemic cerebrovascular disease combined with iron deficiency or haemoglobin deficiency is 45% in the control group.1 2 According to the previous studies, the relative improvement rate of iron treatment for cognitive impairment in patients with iron deficiency is about 25%,911 and it is conservatively estimated that the 3-month risk of VCI in patients with ischaemic cerebrovascular disease combined with iron deficiency or haemoglobin deficiency treated by iron supplementation is 35%. Proportional risk reduction of 25% (rate ratio=0.75). We estimated that 1006 eligible patients (503 for each arm) are required. As 20% of patients are mild anaemia or low haemoglobin,4 5 we will screen about 5030 patients in total.