title: Risk Factors for Growth of Intracranial Aneurysms: A Systematic Review and Meta-Analysis.
abstract: OBJECTIVE
  Understanding risk factors for intracranial aneurysm growth is important for patient management. We performed a meta-analysis examining risk factors for intracranial aneurysm growth in longitudinal studies and examined the association between aneurysm growth and rupture.
  
  
  METHODS
  We searched the literature for longitudinal studies of patients with unruptured aneurysms. We examined the associations of demographics, multiple aneurysms, prior subarachnoid hemorrhage, family history of aneurysm or subarachnoid hemorrhage, smoking, and hypertension; and aneurysm shape, size, and location with aneurysm growth. We studied the association between aneurysm growth and rupture. A meta-analysis was performed by using a random-effects model by using summary statistics from included studies.
  
  
  RESULTS
  Twenty-one studies including 3954 patients with 4990 aneurysms with 13,294 aneurysm-years of follow-up were included. The overall proportion of growing aneurysms was 3.0% per aneurysm-year (95% CI, 2.0%-4.0%). Patient risk factors for growth included age older than 50 years (3.8% per year versus 0.9% per year, P < .01), female sex (3.2% per year versus 1.3% per year, P < .01), and smoking history (5.5% per year versus 3.5% per year, P < .01). Characteristics associated with higher growth rates included cavernous carotid artery location (14.4% per year), nonsaccular shape (14.7% per year versus 5.2% per year for saccular, P < .01), and aneurysm size (P < .01). Aneurysm growth was associated with a rupture rate of 3.1% per year compared with 0.1% per year for stable aneurysms (P < .01).
  
  
  CONCLUSIONS
  Observational evidence provided multiple clinical and anatomic risk factors for aneurysm growth, including age older than 50 years, female sex, smoking history, and nonsaccular shape. These findings should be considered when counseling patients regarding the natural history of unruptured intracranial aneurysms.
authors.affiliation: From the Departments of Radiology (W.B., Y.-Q.Z., G.L., H.J.C., D.F.K.) Brinjikji.waleed@mayo.edu.
authors.forename: W
authors.identifier: http://orcid.org/0000-0001-5271-5524
authors.initials: W
authors.lastname: Brinjikji
authors.affiliation: From the Departments of Radiology (W.B., Y.-Q.Z., G.L., H.J.C., D.F.K.).
authors.forename: Y-Q
authors.identifier: http://orcid.org/0000-0001-5476-9075
authors.initials: YQ
authors.lastname: Zhu
authors.affiliation: From the Departments of Radiology (W.B., Y.-Q.Z., G.L., H.J.C., D.F.K.) Neurosurgery (G.L., H.J.C., D.F.K.).
authors.forename: G
authors.identifier: http://orcid.org/0000-0003-1479-465X
authors.initials: G
authors.lastname: Lanzino
authors.affiliation: From the Departments of Radiology (W.B., Y.-Q.Z., G.L., H.J.C., D.F.K.) Neurosurgery (G.L., H.J.C., D.F.K.).
authors.forename: H J
authors.identifier: http://orcid.org/0000-0003-2590-3815
authors.initials: HJ
authors.lastname: Cloft
authors.affiliation: Center for Science of Healthcare Delivery (M.H.M., Z.W.), Mayo Clinic, Rochester, Minnesota.
authors.forename: M H
authors.identifier: http://orcid.org/0000-0001-5502-5975
authors.initials: MH
authors.lastname: Murad
authors.affiliation: Center for Science of Healthcare Delivery (M.H.M., Z.W.), Mayo Clinic, Rochester, Minnesota.
authors.forename: Z
authors.identifier: http://orcid.org/0000-0002-9368-6149
authors.initials: Z
authors.lastname: Wang
authors.affiliation: From the Departments of Radiology (W.B., Y.-Q.Z., G.L., H.J.C., D.F.K.) Neurosurgery (G.L., H.J.C., D.F.K.).
authors.forename: D F
authors.identifier: http://orcid.org/0000-0002-8495-0040
authors.initials: DF
authors.lastname: Kallmes
mesh_terms: D000367:Age Factors; D000368:Aged; D017542:Aneurysm, Ruptured / Q000473:pathology*; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000473:pathology*; D008137:Longitudinal Studies; D008297:Male; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects