Study Overview

Title of Study

Strategy to obtain warfarin or direct oral anticoagulant’s benefit by evaluating registry: Strawberry study

Study Representative

Naoki Saji

Study Objective

To clarify oral anticoagulant use by patients with non-valvular atrial fibrillation (NVAF) and ascertain its effect on cerebrovascular disorders and cognitive dysfunction

Study Design

Multicenter, prospective, observational study


Patients diagnosed with NVAF who are taking an oral anticoagulant (warfarin, dabigatran, rivaroxaban, apixaban, or edoxaban) at the time of enrollment

Eligibility criteria

Inclusion criteria
Patients with NVAF who:
1. are taking an oral anticoagulant at the time of enrollment
2. can undergo a brain magnetic resonance imaging (MRI) at the time of enrollment
3. have provided informed consent in writing
4. are between the ages of 40 and 84 years at the time of enrollment
5. have a Clinical Dementia Rating (CDR) global score of 0 to 0.5 and a Mini-Mental State Examination (MMSE) score of 20 to 30
6. and are accompanied by a study partner (someone who knows how the patient lives)

Exclusion criteria
1. Patients with valvular atrial fibrillation
2. Patients unable to undergo MRI examination, or MRI cannot be evaluated due to body movement, etc.
3. Patients with dementia with a CDR global score ≥1 or MMSE <20
4. 6 months or less since occurrence of stroke
5. ≤6 years of education
6. Judged by an investigator to be ineligible to participate as a study subject

Observation period

Investigations will be performed annually for 3 years after enrollment, until death or informed consent is withdrawn, whichever comes first.


Primary endpoint
Change in MMSE from time of enrollment until 3 years after enrollment

Secondary endpoints
1. Change in Montreal Cognitive Assessment (MoCA) from time of enrollment until 3 years after enrollment
2. Time until occurrence of any death, stroke, or cardiovascular event
3. Change in CDR global score from time of enrollment until 3 years after enrollment
4. Change in Clinical Dementia Rating Sum of Boxes (CDR-SB) score from time of enrollment
5. Time until hemorrhagic or ischemic event

Expected number of subjects enrolled

400 subjects are expected to be enrolled in the study overall.

Rationale for sample size

The sample size required for repeated-measure data analysis based on a mixed effect model, with age and sex as covariates, at a two-tailed significance level of 5%, and a statistical power of 95%, assuming a few subjects will be excluded from analysis, is 160 subjects in the warfarin group, and 240 subjects in the DOAC group.

Planned time period

March 7, 2017 to March 31, 2023

Study Secretariat

Strawberry study Secretariat
Center for Comprehensive Care and Research on Memory Disorders, National Center for Geriatrics and Gerontology
7-430 Morioka, Obu, Aichi Prefecture 474-8511, Japan
TEL: +81-562-46-2311 (ext. 3123)
FAX: +81-562-46-8394