Epidemiology of cerebral microbleeds and risk of adverse outcomes in atrial fibrillation: a systematic review and meta-analysis

Aims: The aim of this study is to perform a systematic review and meta-analysis on the epidemiology of cerebral microbleeds (CMBs) and the risk of intracranial haemorrhage (ICH) and ischaemic stroke (IS) in patients with atrial fibrillation (AF). Methods and results: PubMed and EMBASE databases were systematically searched from inception to 6 March 2021. All studies reporting the prevalence of CMBs and incidence of ICH and IS in AF patients with and without CMBs were included. Meta-analysis was conducted using random-effect models; odds ratios (ORs), 95% confidence intervals (CIs), and prediction intervals (PIs) were calculated for each outcome. Subgroup analyses were performed according to the number and localization of CMBs. A total of 562 studies were retrieved, with 17 studies finally included in the meta-analysis. Prevalence of CMBs in AF population was estimated at 28.3% (95% CI: 23.8-33.4%). Individuals with CMBs showed a higher risk of ICH (OR: 3.04, 95% CI: 1.83-5.06, 95% PI 1.23-7.49) and IS (OR: 1.78, 95% CI: 1.26-2.49, 95% PI 1.10-2.87). Patients with ≥5 CMBs showed a higher risk of ICH. Metaregression showed how higher of prevalence of diabetes mellitus in AF cohort is associated with higher prevalence of CMBs. Conclusions: Cerebral microbleeds are common in patients with AF, found in almost one out of four subjects. Cerebral microbleeds were associated with both haemorrhagic and thromboembolic events in AF patients. Moreover, the risk of ICH increased consistently with the burden of CMBs. Cerebral microbleeds may represent an important overlooked risk factor for both ICH and IS in adults with AF.