Blood Harmane (1-methyl-9H-pyrido[3,4-b]indole) and Mercury in Essential Tremor: A Population-Based, Environmental Epidemiology Study in the Faroe Islands

• Published in: Neuroepidemiology
• Main Authors: Louis, ED, Eliasen, EH, Ferrer, M, Iglesias Hernandez, D, Gaini, S, Jiang, W, Zheng, W, Nielsen, F, Petersen, MS
• Format: Text
• Language: English
• Published: 2020
• Subjects: Article; Faroe Islands
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7210050/; http://www.ncbi.nlm.nih.gov/pubmed/32007995; https://doi.org/10.1159/000505874

BACKGROUND: Essential tremor (ET) is among the most prevalent neurological diseases. Its environmental determinants are poorly understood. Harmane (1-methyl-9H-pyrido[3,4-b]indole), a dietary tremor-producing neurotoxin, has been linked to ET in a few studies in New York and Madrid. Mercury, also a tremor-producing neurotoxin, has not been studied in ET. The Faroe Islands have been the focus of epidemiological investigations of numerous neurological disorders. OBJECTIVE: In this population-based, case-control study, we directly measured blood harmane concentrations [HA] and blood mercury concentrations [Hg] in ET cases and controls. METHODS: 1,328 Faroese adults were screened; 26 ET cases were identified whose [HA] and [Hg] were compared to 197 controls. RESULTS: Although there were no statistically significant differences between diagnostic groups, median [HA] was 2.7x higher in definite ET (4.13 g(−10)/ml) and 1.5x higher in probable ET (2.28 g(−10)/ml) than controls (1.53 g(−10)/ml). Small sample size was a limitation. For definite ET vs. controls, p = 0.126. [Hg] were similar between groups. CONCLUSIONS: We demonstrated marginally elevated [HA] in definite and probable ET. These data are similar to those previously published, and possibly extend etiological links between this neurotoxin and ET to a third locale. The study did not support a link between mercury and ET.