Prevalence and associations of cerebral microbleeds in an Australian memory clinic cohort.

Background: Cerebral microbleeds (CMBs) are small brain haemorrhages, identified by magnetic resonance imaging (MRI). They indicate potential for cognitive decline and mortality in memory clinic attendees. The presence of more than four CMBs is exclusionary for some clinical trials of disease-modifying therapies for Alzheimer's disease (AD). The prevalence and clinical relevance of CMBs in Australian memory clinic populations has not been reported.

Aims: To highlight the prevalence of CMBs in an Australian memory clinic cohort and explore associations with diagnoses, topography and cognitive performance.

Methods: We conducted a retrospective cohort study of 393 patients who attended a memory clinic (CDAMS) in Melbourne, Australia from January 2014 to December 2016 who underwent brain MRI. Data collected included age, gender, clinical diagnosis and cognitive scores. Univariable and multivariable regression analyses were performed to identify associations of CMBs with clinical and cognitive findings.

Results: The prevalence of CMBs was 27% (n=107) with good inter-rater reliability (κ=0.75). CMBs were significantly associated with increasing age. Prevalence of CMBs was higher in people with mild cognitive impairment (MCI) (32%) and dementia (39%) compared with other diagnostic groups (p<0.001). Lobar-predominant CMB distribution was associated with AD diagnosis. Presence of multiple CMBs was associated with poorer cognitive performance overall.

Conclusions: CMBs are common in an Australian memory clinic population and are associated with poorer cognitive performance. "Real world" prevalence of CMBs may limit accessibility to disease-modifying therapies for many people.