Understanding the risk factors for the formation of de novo intracranial aneurysms (IAs) is important for patients who have ever suffered a cerebral aneurysm. To estimate the risk factors for the development of a de novo IA to identify which patients need more aggressive surveillance after aneurysm treatment. We followed the preferred reporting items for systematic reviews and meta-analyses guidelines and searched the PubMed, CENTRAL, EMBASE, and LILACS databases using the key words cerebral aneurysms, de novo, IAs, risk factors combined using and/or. The search was performed in July 2017.We calculated odds ratios (ORs) and 95% confidence intervals (CIs) using RevMan 5.3 (Cochrane, London, United Kingdom) to evaluate risk factors. Statistical significance was set at P<.05. The analysis included 14 studies involving 6389 patients, of whom 197 patients had de novo IAs. The main risk factors for formation included sex (OR=1.82, 95% CI [1.30,2.56], P=.0005, female vs male), age<40 yr (OR=2.96, 95% CI [1.76,4.96], P<.0001), family history (OR=2.05, 95% CI [1.07,3.93], P=.03), smoking history (OR=2.73, 95% CI [1.81,4.12], P<.0001), and multiple saccular intracranial aneurysms (sIAs) at first diagnosis (OR=2.10, 95% CI [1.12,3.91], P=.02), internal carotid artery (ICA) as the initial site (OR=2.58, 95% CI [1.43,4.68], P=.002). Heterogeneous analysis showed that these I2 were less than 50% and the results were reliable. Observational evidence identified multiple clinical and anatomic risk factors for the formation of de novo IAs, including female sex, age<40 yr, family history, smoking history, multiple sIAs at first diagnosis, and IC as the initial site. More aggressive long-term angiographic follow-up with digital subtraction angiography, computed tomography angiography, or magnetic resonance angiography is recommended for these patients.
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