HARMONISATION - A multimodal prospective study of vascular cognitive impairment in multi-ethnic Asians: Cohort profile, progress, current contributions, and future impact.

Vascular cognitive impairment (VCI) describes cerebrovascular disease (CeVD)-associated cognitive disorders regardless of pathogenesis, ranging from a prodrome to dementia. Heterogeneity in the etiology and severity of CeVD, and significant co-occurrence with Alzheimer's disease (AD) pathology has hampered investigations. Research into VCI is especially relevant in Asia, where cognitive impairment and dementia, often due to VCI, grows due to rapidly aging populations and high prevalence of vascular risk factors. This manuscript reviewed the rationale, unique positioning, design, methodology, and findings from the HARMONISATION study, a prospective observational study of VCI and AD in multi-ethnic Asians. HARMONISATION aimed to discover and validate novel biomarkers as effective diagnostic and prognostic tools, and translate findings into improved patient care, disease management and treatment-utilizing comprehensive multimodal clinical, neuroimaging, retinal, and blood biomarker data to address critical research gaps such as the etiology and clinical importance of mixed dementia, relationships between AD and CeVD pathology, and challenges of heterogenous CeVD pathology. HARMONIZATION recruited and deeply phenotyped 700 older multi-ethnic Asians with no cognitive impairment, mild cognitive impairment, and dementia for up to 5 years of follow-up. It has yielded developments in biomarker identification, validation, interactions and analysis methods; disease mechanisms and progression; clinical prognostics for VCI and AD; improved patient care and management; and enabled future development of novel interventions in Asians, and globally. An ongoing extension study will allow up to 10 years follow-up to further explore specific modifiable processes of VCI and the contributions of vascular events to cognitive impairment.