Study: Pesticides may cause dementia

A study is linking dementia and long term exposure to pesticides but some scientists are questioning the results.

The report published in the journal Occupational and Environmental Medicine reveals consistent exposure to pesticides could raise the risk of suffering Alzheimers disease. Spokesman for Soil and Health Organic NZ Steffan Browning says evidence from a study of 600 people discovered workers directly exposed to pesticides were more likely to perform worse in cognitive tests than those who had not been exposed.

In particular, it was discovered that workers exposed to pesticides were twice as likely to drop two points in the "mini mental state exam" - one of nine tests carried out on them, as those who had not been exposed.

The researchers say the mild impairment raises the possibility of neurodegenerative diseases such as Alzheimers disease or other dementias.

Mr Browning says the evidence from the study, coupled with studies of insects under the same conditions and overseas studies, should be enough to discourage the use of many brands of pesticide.

However, Ian Shaw, Professor of Toxicology at the University of Canterbury, says the report doesnt list the pesticides that the vineyard workers were exposed to and therefore it is difficult to explain the results properly. He says as most insecticides work by interfering with the generation of nervous impulses in insects he isnt surprised by the findings relating to humans. But he says it is more difficult to understand how other pesticides, for example fungicides, might affect neurological function.

"The vineyard workers might have been exposed to a complex mixture of pesticides, for example fungicides and insecticides and the results reflect the effects of only one component of the mixture such as insecticides."

"Im not surprised at the findings, but I suspect they are due to insecticide exposure rather than pesticides generally."

Robert Smith from the University of Leeds says the study does not look at dementia and the link it makes "is so tenuous as to be sensationalised, especially from such a small study."