Repeated Pesticide Exposure Increases the Risk of Alzheimer’s

This is one of those studies that show a significant link between two events without proving any cause-and-effect, but cries out for further studies.  A link between occupational exposure to pesticides and the occurrence of dementia or Alzheimer’s is the subject of a report in the journal Neurology.  

Volunteers over 65 from the agricultural community of Cache County, Utah, completed a baseline questionnaire, which included information about exposure to various types of pesticides.  Their cognitive status was assessed at baseline and after 3, 7, and 9 years, using standard tests, including the Mini-Mental State Exam (MMSE).

Out of 3,084 people without dementia at baseline, 572 reported some pesticide exposure (316 organophosphates, 256 organochlorines, 25 carbamates, and 28 methyl bromides).  During the study, which averaged 7.2 years, 500 persons developed dementia (344 as Alzheimer’s). 

After adjusting for baseline age, gender, education level, ApoE4 genotype,  and MMSE, it was found that there was a greater risk for dementia in those exposed to any pesticide:  1.38-times the risk seen for non-exposed participants.  The increased risk for Alzheimer’s disease was similar:  1.42-times.  The risk for Alzheimer’s in those exposed to organophosphates and organochlorines was slightly higher still:  1.49- and 1.53-times.

The Duke and Utah scientists conducted this study because organophosphates and organochlorines inhibit the enzyme acetyl cholinesterase at cell junctions in the nervous system, leading to reduction of acetylcholine.  Three of the 4 drugs on the market for Alzheimer’s counteract acetyl cholinesterase, and increase the amounts of acetylcholine.  So it looks as if there is a mechanism to explain the link between these two pesticides and an increased likelihood of Alzheimer’s disease.  Speculation, but a good reason for further studies.  Until then, not enough evidence to avoid pesticides, but read the labels, and follow safety instructions and precautions.