Pesticide exposure associated with mild cognitive impairment & depression among agricultural workers: Case control study in rural India.

Background & objectives This study was carried out to identify association of chronic pesticide exposure with cognitive impairment, depression, and movement disorder by utilising a comprehensive paradigm of symptom-based validated screening; and estimation of RBC acetylcholinesterase (AChE), plasma butyrylcholinesterase (BChE) and paraoxonase 1 (PON1) levels among high risk rural population, particularly agricultural workers in West Bengal, India. Methods Galsi II block, Purba Bardhaman district, West Bengal was selected as the study site. Samples were drawn among residents aged 50 yr and above of either sex, continuously living in the area for at least last five years. Primary screening was applied to enquire about target neuropsychiatric disorders. On getting an affirmative reply to any of the questions, participants were further screened for cognitive impairment and depression. Any participant screening 'positive' for either of the three conditions fulfilled criteria for recruitment as a 'case'. Blood samples were collected from participants for estimation of AChE, BChE and PON1. Results Of 808 participants, 180 (22.3%) were screened as 'Cases'. Pesticide exposure was a significant risk for detection as a 'Case' [Odds ratio (OR)=2.9], which supports premise of this study. Additionally, male gender (OR=1.98), more years of pesticide exposure (>30 yr) (OR=1.8) and more frequent use of pesticides (1/week) (OR=2.5) were significant risks of screening as a 'Case'. Agricultural workers, who were exclusively engaged with agriculture as occupation, had the lowest cognition score (77.5±19.6) (P<0.001), highest impairment in daily living (2.1±1.7) (P=0.01) and highest BDI (Beck Depression Inventory) score (15±7) (P=0.003), i.e., a higher risk of depression. Paraoxonase 1 (PON1) expression was significantly increased among workers engaged in agricultural activity for more than 8 h in a day (82.3±42) (P=0.03) and who applied pesticides at least once a week (80.3±40) (P=0.02). Interpretation & conclusions This population-based study among rural agricultural population in West Bengal has identified a prevalence of 18.9 per cent of cognitive impairment with or without depression; 8.3 per cent depression with or without cognitive impairment and 1.5 per cent possible movement disorder. We also identified that pesticide exposure is a risk for development of these neuropsychiatric disorders of neuroinflammatory origin. Among biomarkers, PON1 was identified to be significantly higher among participants who spent more hours in agricultural work and applied pesticides more frequently.