Blood concentrations of harmane, a tremor-producing neurotoxin, are elevated in essential tremor (ET). Harmane is also a comutagen. Using a case-control design, we compared the prevalence of cancer in ET cases vs. controls, and determined whether blood harmane concentrations are elevated among ET cases with cancer. 66/267 (24.7%) ET cases vs. 55/331 (16.6%) controls had cancer (adjusted OR 1.52, 95% CI 1.01-2.30, P = 0.04). Among specific cancer types, colon cancer was more prevalent in ET cases than controls (2.6% vs. 0.6%, P = 0.04). Log blood harmane concentration was higher in ET cases vs. controls (P = 0.02) and in participants with vs. without cancer (P = 0.02). Log blood harmane concentration was highest in ET cases with cancer when compared with other groups (P = 0.009). These links between cancer and ET and between high blood harmane and cancer in ET deserve further study.
(c) 2007 Movement Disorder Society.