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

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.