title: Gender Differences in Hiccup Patients: Analysis of Published Case Reports and Case-Control Studies.
abstract: BACKGROUND
  Although sporadic male predominance in hiccup patients has been reported, the association between gender differences and triggering factors has rarely been evaluated in patients with hiccups.
  
  
  OBJECTIVE
  The aim of this study was to investigate whether gender differences exist in hiccup patients by analyzing all previously published hiccup literature containing gender and etiology information.
  
  
  METHODS
  Published literature on this topic was identified using a standardized search strategy in the PubMed, SCOPUS, and CINAHL electronic databases. The literature search included studies published from January 1990 to December 2013. Searches were limited to English-language publications. Of 476 identified studies, 318 studies were eligible including eight case-control studies that contained nonhiccup control groups. Triggering factors for hiccups were categorized into two types: central nervous system (CNS) and non-CNS causes. Odds ratios (ORs) were calculated for the eight case-control studies and event rates for the other studies by meta-analysis. In addition, gender differences and mean ages were analyzed for the case studies.
  
  
  RESULTS
  Pooled OR was 2.42 (95% confidence interval [CI] 1.40-4.17) with inclination for male predominance. Subgroup analysis by cause showed clear male predominance in the non-CNS type with OR of 11.72 (95% CI 3.16-43.50), whereas indistinct in the CNS type with OR of 1.74 (95% CI 0.95-3.16). Of the remaining 310 studies with 864 patients, previous findings were consistent. Male predominance was consistent in non-CNS (85.1%, 95% CI 78.2-90.2) and unknown origin (82.2%, 95% CI 75.8-87.2) patients, whereas mitigating the sex discrepancy in those with CNS origin (65.8%, 95% CI 53.1-76.5).
  
  
  CONCLUSIONS
  We demonstrated male predominance in hiccup patients. This gender difference for hiccups was more pronounced in patients with non-CNS causes, whereas indistinct in patients with CNS causes.
authors.affiliation: Department of Internal Medicine, School of Medicine, Gyeongsang National University, Jinju, Republic of Korea.
authors.forename: Gyeong-Won
authors.initials: GW
authors.lastname: Lee
authors.affiliation: Department of Preventive Medicine, Dong-A University, Busan, Republic of Korea; Environmental Health Center, Dong-A University, Busan, Republic of Korea.
authors.forename: Rock Bum
authors.initials: RB
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, School of Medicine, Gyeongsang National University, Jinju, Republic of Korea.
authors.forename: Se Il
authors.initials: SI
authors.lastname: Go
authors.affiliation: Department of Internal Medicine, School of Medicine, Gyeongsang National University, Jinju, Republic of Korea.
authors.forename: Hyun Seop
authors.initials: HS
authors.lastname: Cho
authors.affiliation: Department of Internal Medicine, School of Medicine, Gyeongsang National University, Jinju, Republic of Korea.
authors.forename: Seung Jun
authors.initials: SJ
authors.lastname: Lee
authors.affiliation: Department of Palliative Care and Rehabilitation Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA.
authors.forename: David
authors.initials: D
authors.lastname: Hui
authors.affiliation: Department of Palliative Care and Rehabilitation Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Bruera
authors.affiliation: Department of Internal Medicine, School of Medicine, Gyeongsang National University, Jinju, Republic of Korea. Electronic address: newatp@gnu.ac.kr.
authors.forename: Jung Hun
authors.initials: JH
authors.lastname: Kang
mesh_terms: D005260:Female; D006606:Hiccup / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D012727:Sex Characteristics
keywords: Hiccup; gender; male; review