Are Pesticides a Risk Factor for Alzheimer Disease?

Jaime Toro, MD

A case–control study suggests an association between DDT exposure and AD risk.

Evidence suggests that long-term pesticide exposure may have toxic effects on the central nervous system. In the U.S., older adults are most likely to have been exposed to persistent pesticide such as dichlorodiphenyltrichloroethane (DDT), which was in use from the 1940s through 1972. Some studies have shown an elevated risk for Alzheimer disease (AD) and Parkinson disease associated with occupational pesticide exposure. To examine the association between DDT exposure and AD risk, researchers conducted a case–control study, using serum samples taken from patients with AD and controls in Texas and Georgia between 2002 and 2008. There were a total of 165 samples, representing 79 control and 86 AD cases (94 women, 71 men; women comprised 60% of controls and 55% of cases). At enrollment, participants completed the Mini-Mental State Examination (MMSE). The investigators measured brain and serum levels of the DDT metabolite dichlorodiphenyldichloroethylene (DDE) and determined apolipoprotein E (APOE) genotype.

The mean DDE level in serum was 3.8-fold higher in AD patients than in controls. Those with the highest tertile of DDE had a fourfold increased risk for AD and had significantly lower MMSE scores. Among those in the highest DDE tertile, APOE ?4 carriers had significantly lower MMSE scores than noncarriers. The authors conclude that elevated levels of DDE are associated with an increased risk for AD and that those with an APOE ?4 allele may be more susceptible to the effect of DDE.

Citation(s):

Richardson JR.Elevated serum pesticide levels and risk for Alzheimer disease. JAMA Neurol 2014 Jan 27; [e-pub ahead of print ].