Increased odds of melanoma: Parkinson's disease, essential tremor, dystonia versus controls

Objective: Patients with Parkinson's disease (PD) have an increased risk of melanoma, although the mechanisms are unclear. We are unaware of studies that have assessed the association between other movement disorders, such as essential tremor (ET) and dystonia, and melanoma. In this study, we assessed the association between ET, PD, dystonia and cancer (esp. melanoma). Methods: One hundred and eight PD cases, 139 ET cases, and 54 dystonia cases, and 124 controls were enrolled in a research study of the epidemiology of movement disorders (total n = 425). The groups were frequency matched on age and gender. Cancer diagnoses were made based on self-reports. Melanoma diagnoses were further validated. Results: The prevalence of melanoma was higher in PD cases than controls (13.9 vs. 1.6%, p < 0.001), and was marginally higher in ET cases (5.8%, p = 0.08) and dystonia cases (7.4%, p = 0.06) than controls. In adjusted logistic regression models, the odds of melanoma was 7.09-9.84 times higher in PD cases than controls (p values 0.01-0.003), 3.73-4.10 times higher in ET cases than controls (p values 0.08-0.10), and 4.88-5.27 times higher in dystonia cases than controls (p values 0.06-0.07). Conclusion: The links between neurological disorders and melanoma, long-known, may not be specific to PD and may extend to other movement disorders.