Objective: The objective of this study is to determine differences in cognitive profiles among Veterans with Essential Tremor (ET) who were exposed to agent orange compared to those without such exposure.

Background: Prior studies have reported that ET is associated with cognitive disturbances. ^1,2. These prior studies have primarily examined rates of dementia in individuals with and without ET. The most common variable associated with cognitive impairment in ET is age of onset; older onset ET is associated with mild cognitive impairment. Our Veterans database allows for analysis of variables unique to this population such as agent orange exposure (AO). Agent Orange is a powerful herbicide, used during the Vietnam war, associated with wide range of conditions including Parkinson’s disease. It includes the active ingredient 2,4,5-trichlorophenoxyacetic acid, as well as 2,3,7,8-tetrachlolodibenzo-p-dioxan (TCDD), which is highly toxic.

Method: Medical records of ET patients, seen in the Parkinson’s Disease Research, Education and Clinical Center (PADRECC), Houston, were reviewed. These patients were seen in the center from September 1, 2001 – March 31, 2018. During the initial visit, cognitive status was recorded either subjectively (present or not), or via bedside testing (MOCA or MMSE). Normal cognition was defined as MOCA ≥ 26 or MMSE ≥ 24.

Results: Medical records of 1465 patients with tremors were reviewed. Of these, 1051 subjects were diagnosed with ET based on MDS ET diagnostic criteria. 658 subjects had normal cognition, 360 had MCI based on cut off scores, and 33 had no documented cognitive assessment. . Of the 1051 subjects, 280 had documented agent orange exposure, 741 had no exposure, and 30 had unknown exposure or no documentation. In subjects exposed to agent orange, 139 (51.1%) had normal cognition and 133 (48.8%) had cognitive impairment. Among non-exposed group, 505 (69.1%) had normal cognition and 225 (30.8%) had cognitive impairment.

Conclusion: In this study, ET patients with agent orange exposure demonstrated a higher association with cognitive impairment compared to non-exposed individuals.

References: 1. Benito-León J, Louis ED, Bermejo-Pareja F; Neurological Disorders in Central Spain (NEDICES) Study Group. Population-based case-control study of cognitive function in essential tremor. Neurology. 2006 Jan 10;66(1):69-74. doi: 10.1212/01.wnl.0000192393.05850.ec. PMID: 16401849.
2. Thawani SP, Schupf N, Louis ED. Essential tremor is associated with dementia: prospective population-based study in New York. Neurology. 2009 Aug 25;73(8):621-5. doi: 10.1212/WNL.0b013e3181b389f1. PMID: 19704081; PMCID: PMC2731620.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cognitive-impairment-and-agent-orange-exposure-in-veterans-with-essential-tremor/