Alzheimer's disease and Pesticides

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Alzheimer's disease and Pesticides
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Environmental Pesticide Exposure as a Risk
Factor for Alzheimer's Disease A Case-Control
Study

• The purpose of this study was to evaluate the
  influence of pesticide exposure on the
  development of Alzheimer's.

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Study Population

• The population studied consisted of 1,924
  individuals in the region of Lac Saint-Jean in
  Quebec, Canada.
• 69 of subjects were women and average age was
  80 yrs old.

4
The Region

• The agroforestry industry is a major economic
  activity in this region of Quebec.
• Many neurotoxic pesticides (lead, arseniate,
  calcium arseniate, DDT, phosphamidon,
  fenitrothion, Novathion, dimethoate, Matacil)
  have been used in forested areas since the
  beginning of the 1930's.

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Methods

• 1st step involved screening for cognitive
  impairment and overview of the health status of
  the subjects.
• 2nd step determined if the subject had dementia.
  The evaluation included a series of
  neuropsychological tests.

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• For the 3rd step, subjects that were considered
  demented were referred to a medical exam.
• Also the data of the Agriculture Census of
  Statistics in Canada from 1971-1991 was used to
  establish the area sprayed with herbicides and
  insecticides.
• The area sprayed was used as a potential
  indicator for environmental exposure to
  pesticides.

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Results

• 122 cases of Alzheimer's disease were diagnosed.
• The study did not establish a significant
  relation between long-term exposure to
  pesticides, insecticides, or herbicides and
  development of Alzheimer's.

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Neurodegenerative Diseases and Exposure to
Pesticides in the Elderly

• Hypothesis exposure to pesticides could be
  related to central nervous system disorders.

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Study Population

• The sample was composed of 1,507 individuals.
• The population studied were elderly people with
  an average age of 78 who lived in the area of
  Gironde in southwest France.

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Methods

• The study was performed over a six year
  interval. From 1992-1998.
• Detailed occupational histories were generated
  for all subjects from specific questionnaires.
• The study considered that workers and owners of
  small farms had experienced higher exposure since
  they had mixed and sprayed pesticides.

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Methods

• A questionnaire classified subjects as being
  suspected of having dementia.
• If subjects were suspected of having dementia,
  they were evaluated by a neurologist to confirm
  information.

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Results

• It was found an association between past
  occupational exposure to pesticides with an
  increase in the risk of developing Alzheimer's
  disease.
• The relation appeared exclusively in men.
• Pesticide treatment tasks are performed almost
  exclusively by males.

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Results

• The number of pesticides used on any given farm
  each year is from 3-23.
• It was not possible to determine what types of
  pesticides were responsible for the effects
  observed.

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Reasons for difference in results

• The first study used retrospective data.
• The second study was developed over a period of
  six years (1992-1998).
• For the second study people were more in direct
  contact with pesticides.

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Reasons for difference in results

• In the second study only the exposure during the
  period preceding the appearance of Alzheimer's
  disease symptoms was considered.

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Reasons for difference in results

• In the second study, historical data on aerial
  spraying was analyzed. The analysis of historical
  data on aerial spraying of insecticides on the
  Lac Saint-Jean forest from 1930 to 1994 indicates
  that the pesticides did not seem to reach
  residential areas.