Silent brain infarctions and cognition decline: systematic review and meta-analysis.

BACKGROUND: Silent 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.

METHODS: The 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.

RESULTS: Thirty 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.

CONCLUSIONS: SBI are associated with worse cognition and increased risk for dementia. More standardization of cognitive assessment methods would facilitate future cross-study comparisons.