• Feeha Azeem, Romella Durrani, Charlotte Zerna, and Eric E Smith.
• Neurology, Department of Clinical Neurosciences, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada.
• J. Neurol. 2020 Feb 1; 267 (2): 502-512.

BackgroundSilent brain infarction (SBI) may be associated with cognitive decline in the general population. We systematically reviewed prior literature on: (1) SBI and cognition cross-sectionally; (2) baseline SBI and future cognitive decline and risk for cognitive disorders including dementia, and (3) incident SBI and the emergence of cognitive decline or cognitive disorders.MethodsThe MEDLINE and EMBASE databases were searched for relevant studies. Data were independently extracted by two reviewers. Quality was assessed using the Newcastle Ottawa Scale. Data were pooled using a random effects model when more than two comparable estimates were found.ResultsThirty relevant studies were identified: 17 had a cross-sectional design, 10 evaluated the association of baseline SBI with future cognitive decline, and 5 evaluated the association of incident SBI with cognitive decline. Most cross-sectional studies reported lower cognitive performance in persons with SBI. The pooled risk for incident dementia in persons with SBI was 1.48 (95% CI 1.12-1.97), but there was significant heterogeneity (p = 0.009); removing one outlier eliminated the heterogeneity (p = 0.53), giving a lower but still significant estimate (hazard ratio 1.27, 95% CI 1.06-1.51). The pooled risk for incident MCI was not increased in persons with SBI (hazard ratio 0.83, 95% CI 0.40 to 1.72), but there was significant heterogeneity (p < 0.001). The appearance of new SBI was associated with steeper rate of cognitive decline and the appearance of dementia.ConclusionsSBI are associated with worse cognition and increased risk for dementia. More standardization of cognitive assessment methods would facilitate future cross-study comparisons.

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