title: Association between hospital volume and outcomes of elderly and non-elderly patients with acute biliary diseases: a national administrative database analysis.
abstract: OBJECTIVE
  This study aimed to investigate the relationship between hospital volume and clinical outcomes of elderly and non-elderly patients with acute biliary diseases using data from a national administrative database.
  
  
  METHODS
  Overall, 26720 elderly and 33774 non-elderly patients with acute biliary diseases were referred to 820 hospitals in Japan. Hospital volume was categorized into three groups based on the case numbers during the study period: low-volume, medium-volume and high-volume. We compared the risk-adjusted length of stay (LOS) and in-hospital mortality in relation to hospital volume. These analyses were stratified according to the presence of invasive treatments for acute biliary diseases.
  
  
  RESULTS
  Multiple linear regression analyses showed that increased hospital volume was significantly associated with shorter LOS in both elderly and non-elderly patients with and without invasive treatments. Increased hospital volume was significantly associated with decreased relative risk of in-hospital mortality in elderly patients. The odds ratio for high-volume hospitals was 0.672 in elderly patients without invasive treatments (95% confidence interval [CI] 0.533-0.847, P=0.001) and 0.715 in those with invasive treatments (95% C, 0.566-0.904, P=0.005). However, no significant differences for in-hospital mortality were seen in non-elderly patients with and without invasive treatments.
  
  
  CONCLUSIONS
  This study has highlighted that higher volume hospitals significantly reduced LOS and in-hospital mortality for elderly patients with acute biliary diseases, but not non-elderly patients. The current results are of value for elderly healthcare policy decision-making, and highlight the need for further studies into the quality of care for elderly patients.
authors.affiliation: Department of Preventive Medicine and Community Health, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan. amurata@med.uoeh-u.ac.jp
authors.forename: Atsuhiko
authors.initials: A
authors.lastname: Murata
authors.forename: Shinya
authors.initials: S
authors.lastname: Matsuda
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Kuwabara
authors.forename: Yukako
authors.initials: Y
authors.lastname: Ichimiya
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Matsuda
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Kubo
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Fujino
authors.forename: Kenji
authors.initials: K
authors.lastname: Fujimori
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Horiguchi
mesh_terms: D000208:Acute Disease; D000368:Aged; D001660:Biliary Tract Diseases / Q000401:mortality / Q000628:therapy*; D005260:Female; D017052:Hospital Mortality / Q000639:trends; D006761:Hospitals / Q000706:statistics & numerical data*; D006801:Humans; D007564:Japan / Q000453:epidemiology; D007902:Length of Stay / Q000639:trends; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D017063:Outcome Assessment, Health Care / Q000379:methods*; D015996:Survival Rate / Q000639:trends