title: Prospective study of the correlation between admission plasma homocysteine levels and neurological outcome following subarachnoid hemorrhage: a case for the reverse epidemiology paradox?
abstract: BACKGROUND
  Homocysteine (tHcy) has been known over the last few decades for its putative impact on vascular diseases, but has not been evaluated much in patients with subarachnoid hemorrhage (SAH). This study was carried out to assess its prognostic impact on the neurological outcome following SAH.
  
  
  METHODS
  Admission plasma tHcy was evaluated in 90 SAH patients and prospectively studied in relation to various factors and the Glasgow Outcome Scale (GOS) at 3 months. Univariate and multivariate analyses were performed using SPSS 21.
  
  
  RESULTS
  tHcy was significantly higher following SAH compared to matched controls [median (IQR): 25.7 (17.3-35.9) vs. 14.0 (9.8-17.6) μmol/l, p < 0.001]. It was significantly higher in younger patients. However, systemic disease, WFNS and Fisher grades did not have a significant impact on its levels. tHcy was significantly lower among patients who died [median (IQR): 16.0 (14.4-20.6) vs. 29.7 (21.8-40.2) μmol/l, p < 0.001] and those with unfavorable outcome (GOS 1-3) [median (IQR): 21.6 (14.5-28.2) vs. 30.3 (20.4-40.7) μmol/l, p = 0.004] compared to others, with a significant continuous positive correlation between tHcy and GOS (p = 0.002). The beneficial association of tHcy with outcome was homogeneous with no significant subgroup difference. Multivariate analysis using binary logistic regression adjusting for the effects of age, systemic disease, WFNS grade, Fisher grade, site of aneurysm, clipping or coiling revealed higher tHcy to have a significant independent association with both survival (p = 0.01) and favorable outcome (p = 0.04).
  
  
  CONCLUSIONS
  Higher homocysteine levels following SAH appear to have a significant association with both survival and favorable neurological outcome, independent of other known prognostic factors, apparently exemplifying "reverse epidemiology paradox" in which a conventional risk factor seems to impart a survival advantage.
authors.affiliation: Department of Neurosurgery, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, 160012, India, ssdhandapani.neurosurg@gmail.com.
authors.forename: Sivashanmugam
authors.initials: S
authors.lastname: Dhandapani
authors.forename: Sachin
authors.initials: S
authors.lastname: Goudihalli
authors.forename: Kanchan K
authors.initials: KK
authors.lastname: Mukherjee
authors.forename: Harnarayan
authors.initials: H
authors.lastname: Singh
authors.forename: Anirudh
authors.initials: A
authors.lastname: Srinivasan
authors.forename: Mohammad
authors.initials: M
authors.lastname: Danish
authors.forename: Shanthanam
authors.initials: S
authors.lastname: Mahalingam
authors.forename: Manju
authors.initials: M
authors.lastname: Dhandapani
authors.forename: Sunil K
authors.initials: SK
authors.lastname: Gupta
authors.forename: N
authors.initials: N
authors.lastname: Khandelwal
authors.forename: Suresh N
authors.initials: SN
authors.lastname: Mathuriya
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D023261:Glasgow Outcome Scale; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011379:Prognosis; D011446:Prospective Studies; D012307:Risk Factors; D013345:Subarachnoid Hemorrhage / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology
chemical_list: D006710:Homocysteine