title: Blood harmane (1-methyl-9H-pyrido[3,4-b]indole) concentration in essential tremor cases in Spain.
abstract: BACKGROUND
  Environmental correlates for essential tremor (ET) are largely unexplored. The search for such environmental factors has involved the study of a number of neurotoxins. Harmane (1-methyl-9H-pyrido[3,4-b]indole) is a potent tremor-producing toxin. In two prior case-control studies in New York, we demonstrated that blood harmane concentration was elevated in ET patients vs. controls, and especially in familial ET cases. These findings, however, have been derived from a study of cases ascertained through a single tertiary referral center in New York.
  
  
  OBJECTIVE
  Our objective was to determine whether blood harmane concentrations are elevated in familial and sporadic ET cases, ascertained from central Spain, compared to controls without ET.
  
  
  METHODS
  Blood harmane concentrations were quantified by a well-established high performance liquid chromatography method.
  
  
  RESULTS
  The median harmane concentrations were: 2.09 g(-10)/ml (138 controls), 2.41 g(-10)/ml (68 sporadic ET), and 2.90 g(-10)/ml (62 familial ET). In an unadjusted logistic regression analysis, log blood harmane concentration was not significantly associated with diagnosis (familial ET vs. control): odds ratio=1.56, p=0.26. In a logistic regression analysis that adjusted for evaluation start time, which was an important confounding variable, the odds ratio increased to 2.35, p=0.049.
  
  
  CONCLUSIONS
  Blood harmane levels were slightly elevated in a group of familial ET cases compared to a group of controls in Spain. These data seem to further extend our observations from New York to a second cohort of ET cases in Spain. This neurotoxin continues to be a source of interest for future confirmatory research.
authors.affiliation: Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY, USA. EDL2@columbia.edu
authors.forename: Elan D
authors.initials: ED
authors.lastname: Louis
authors.forename: Julian
authors.initials: J
authors.lastname: Benito-León
authors.forename: Sara
authors.initials: S
authors.lastname: Moreno-García
authors.forename: Saturio
authors.initials: S
authors.lastname: Vega
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Romero
authors.forename: Felix
authors.initials: F
authors.lastname: Bermejo-Pareja
authors.forename: Marina
authors.initials: M
authors.lastname: Gerbin
authors.forename: Amanda S
authors.initials: AS
authors.lastname: Viner
authors.forename: Pam
authors.initials: P
authors.lastname: Factor-Litvak
authors.forename: Wendy
authors.initials: W
authors.lastname: Jiang
authors.forename: Wei
authors.initials: W
authors.lastname: Zheng
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D002851:Chromatography, High Pressure Liquid; D004785:Environmental Pollutants / Q000009:adverse effects / Q000097:blood*; D020329:Essential Tremor / Q000097:blood* / Q000139:chemically induced / Q000453:epidemiology / Q000503:physiopathology; D005260:Female; D006247:Harmine / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000097:blood; D006801:Humans; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D020258:Neurotoxicity Syndromes / Q000097:blood* / Q000453:epidemiology / Q000503:physiopathology; D016017:Odds Ratio; D018570:Risk Assessment; D012307:Risk Factors; D013030:Spain / Q000453:epidemiology; D015854:Up-Regulation
chemical_list: D004785:Environmental Pollutants; D006247:Harmine; C005010:harman