Occupational pesticide exposure and screening tests for neurodegenerative disease among an elderly population in Costa Rica

Rollins School of Public Health, Emory University, 1518 Clifton Road, Atlanta, United States. Electronic address: .
Environmental Research (Impact Factor: 3.95). 10/2012; 120. DOI: 10.1016/j.envres.2012.08.014
Source: PubMed

ABSTRACT BACKGROUND: Pesticides have been associated with Parkinson's disease (PD) in many studies, and with Alzheimer's disease (AD) in a few. METHODS: We conducted screening tests for neurologic disease and occupational pesticide use in a population-based sample of 400 elderly subjects at two government-run clinics in Costa Rica; 361 subjects who failed the initial screen were given both the Mini-mental States Exam (MMSE) and a modified version of a 10-item United Parkinson's Disease Rating Motor Subscale (UPDRS). Among subjects who failed either test, 144 were then examined by a neurologist. RESULTS: Past occupational pesticide exposure was reported by 18% of subjects. Exposed subjects performed worse on the MMSE than the non-exposed (mean 24.5 versus 25.9, p=0.01, adjusted for age, sex, and education). The exposed had significantly elevated risks of abnormal scores on two UPDRS items, tremor-at-rest (OR 2.58, 1.28-5.23), and finger-tapping (OR=2.94, 95% CI 1.03-8.41). Thirty-three (23%) of those examined by the neurologist were diagnosed with possible/probable PD, 3-4 times the expected based on international data; 85% of these cases had not been previously diagnosed. Among subjects who took the UPDRS, the exposed had an increased risk of PD (OR=2.57, 95% CI 0.91-7.26). No excess risk was found for a diagnosis of AD or mild cognitive impairment. CONCLUSIONS: Elderly subjects with past occupational pesticide exposure performed significantly worse on screening tests for dementia and PD, and had an increased risk of an eventual PD diagnosis. Screening may be particularly appropriate among elderly subjects with past pesticide exposure.

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    ABSTRACT: Background: We previously screened 400 elderly Costa Ricans for neurodegenerative disease. Those reporting occupational pesticide exposure (18%) had an increased Parkinson's disease (PD) risk (OR 2.57, 95% CI 0.91-7.26), and worse cognition (Mini-Mental States Exam (MMSE) 24.5 versus 25.9 points, p=0.01). We subsequently measured long-lasting organochlorine pesticides (beta-HCH,DDE, DDT, and dieldrin) in a sub-sample (n=89). Dieldrin and beta-HCH have been linked to PD, and DDE to Alzheimer's disease. Methods: We ran regression models for MMSE and tremor-at-rest to assess associations with pesticides in 89 subjects. Results: The percent of beta-HCH, DDE, DDT (parent compound for DDE), and dieldrin above their limit of detection (LOD) were 100%, 93%, 75%, and 57%, respectively. Tremor-at-rest was found in 21 subjects, and the mean MMSE was 25. Those who reported occupational pesticide exposure (n=36) had more detectable dieldrin samples (p=0.005), and higher mean levels of dieldrin (p=0.01), than those not reporting exposure. Other pesticides did not differ between those with and without self-reported occupational exposure. There was a positive but non-significant trend of higher risk for tremor-at-rest with higher dieldrin (p=0.10 for linear trend). Neither DDE nor DDT showed a relationship with MMSE. However, after excluding two outliers with the lowest MMSE scores, higher DDT levels showed some modest association with lower MMSE (p=0.09 for linear trend). Conclusions: Our data are limited by small sample size. However, dieldrin was high in our population, has been previously linked to PD, and could be partly responsible for the excess PD risk seen in our population.
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    ABSTRACT: Health effects of pesticides are easily diagnosed when acute poisonings occurs, nevertheless, consequences from chronic exposure can only be observed when neuropsychiatric, neurodegenerative or oncologic pathologies appear. Therefore, early monitoring of this type of exposure is especially relevant to avoid the consequences of pathologies previously described; especially concerning workers exposed to pesticides on the job. For acute organophosphate pesticides (OPP) exposure, two biomarkers have been validated: plasma cholinesterase (ChE) and acetylcholinesterase (AChE) from erythrocytes. These enzymes become inhibited when people are exposed to high doses of organophosphate pesticides, along with clear signs and symptoms of acute poisoning; therefore, they do not serve to identify risk from chronic exposure. This study aims to assess a novel biomarker that could reflect neuropsychological deterioration associated with long-term exposure to organophosphate pesticides via the enzyme acylpeptide-hydrolase (ACPH), which has been recently identified as a direct target of action for some organophosphate compounds. Three population groups were recruited during three years (2011-2013): Group I having no exposure to pesticides, which included people living in Chilean coastal areas far from farms (external control); Group II included those individuals living within the rural and farming area (internal control) but not occupationally exposed to pesticides; and Group III living in rural areas, employed in agricultural labour and having had direct contact with pesticides for more than five years. Blood samples to assess biomarkers were taken and neuropsychological evaluations carried out seasonally; in three time frames for the occupationally exposed group (before, during and after fumigation period); in two time frames for internal control group (before and during fumigation), and only once for the external controls. Neuropsychological evaluations considered cognitive functions, affectivity and psychomotor activity. The biomarkers measured included ChE, AChE and ACPH. Statistical analysis and mathematical modelling used both laboratory results and neuropsychological testing outcomes in order to assess whether ACPH would be acceptable as biomarker for chronic exposure to OPP. This study protocol has been implemented successfully during the time frames mentioned above for seasons 2011, 2012 and 2013-2014.
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