title: Research productivity in neurosurgery: trends in globalization, scientific focus, and funding.
abstract: OBJECTIVE
  While research is important for the survival, growth, and expansion of neurosurgery, little work has been done to quantify the status and trends of neurosurgical publications. The purpose of this bibliometric study was to quantitatively analyze trends in neurosurgical publications, including changes in worldwide productivity, study methodology, subspecialty topic, and funding.
  
  
  METHODS
  This was a retrospective bibliometric study using MEDLINE to record all publications between 1996 and 2009 by first authors affiliated with neurosurgical departments. Country of origin, MEDLINE-defined methodology, study topic, and funding sources (for US articles) were recorded. Linear regression was used to derive growth rates.
  
  
  RESULTS
  Total articles numbered 53,425 during the study period, with leading global contributors including the US with 16,943 articles (31.7%) and Japan with 10,802 articles (20.2%). Countries demonstrating rapid growth in productivity included China (121.9 ± 9.98%/year, p < 0.001), South Korea (50.5 ± 4.7%/year, p < 0.001), India (19.4 ± 1.8%/year, p < 0.001), and Turkey (25.3 ± 2.8%/year, p < 0.001). While general research articles, case reports, and review articles have shown steady growth since 1996, clinical trials and randomized controlled trials have declined to 2004 levels. The greatest overall subspecialty growth was seen in spine surgery. Regarding funding, relative contribution of National Institutes of Health (NIH)-funded publications decreased from 30.2% (290 of 959) to 22.5% (356 of 1229) between 1996 and 2009.
  
  
  CONCLUSIONS
  Neurosurgical publications demonstrate continued increases in productivity as well as in global expansion, although US contributions remain dominant. Two challenges that the neurosurgical community is facing include the preponderance of case reports and review articles and the relative decline in NIH funding for US neurosurgical publications, as productivity has outpaced government financial support.
authors.affiliation: Department of Neurosurgery, David Geffen School of Medicine at UCLA, Los Angeles, California 90095-7039, USA. jhauptman@mednet.ucla.edu
authors.forename: Jason S
authors.initials: JS
authors.lastname: Hauptman
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Chow
authors.forename: Neil A
authors.initials: NA
authors.lastname: Martin
authors.forename: Michael W
authors.initials: MW
authors.lastname: Itagaki
mesh_terms: D015706:Bibliometrics; D035843:Biomedical Research / Q000706:statistics & numerical data / Q000639:trends*; D006801:Humans; D038622:Internationality; D016239:MEDLINE / Q000706:statistics & numerical data; D009493:Neurosurgery / Q000706:statistics & numerical data / Q000639:trends*; D011643:Publishing / Q000706:statistics & numerical data / Q000639:trends*; D012109:Research Support as Topic / Q000706:statistics & numerical data / Q000639:trends*; D012189:Retrospective Studies; D014481:United States