Low Dose Exposure to Organochlorine Pesticides Linked to Cognitive Impairment

Individuals subjected to chronic low-dose exposure to organochlorine pesticides show an increased risk of cognitive impairment in later life. The study is published in Environmental International.

Organochlorine pesticides (OCPs) are a group of environmental contaminants that were banned in developed countries 20-30 years ago. But since they accumulate through the food chain and remain for a very long time in the human body, especially adipose tissue, high levels can still be found in a majority of the population of Sweden, as well as in most other industrial countries. The most commonly known of these compounds is the pesticide DDT.

The research group at Uppsala University has previously shown associations between environmental contaminants and diabetes, atherosclerosis and stroke. Using the same large data set they have now shown that the OCPs are related to future cognitive impairment.

The PIVUS study (Prospective Investigation of Uppsala Seniors) comprised of around 1,000 70-year-olds in Uppsala who have been studied over a longer period of time. The researchers measured three different OCPs in plasma from the individuals and investigated who received a diagnosis of cognitive impairment over a 10-year period.

The results show that individuals with high levels of three OCPs (p,p’-DDE (a metabolite of DDT), transnona-chlordane and hexachlorobenzene) had about 3 times higher future risk of cognitive impairment than those with low levels of OCP. The results are independent of factors such as sex, smoking, diabetes, exercise habits, alcohol intake, weight change and high blood pressure.

Image shows a person using DDT for mosquito control.

The results show that individuals with high levels of three OCPs, transnona-chlordane and hexachlorobenzene) had about 3 times higher future risk of cognitive impairment than elders with low levels of OCP. Image is for illustrative purposes only and a person using DDT for mosquito control. Credit: CDC.

“Even though OCPs are well-known neurotoxins, our findings are surprising because current exposure levels of these chemicals are very low. However, our study subjects were the first generation with almost life-time exposure to these chemicals. Thus, we found evidence that low-dose, but chronic, exposure of OCPs can be harmful to the human brain,” says Lars Lind, Professor of Medicine at Uppsala University.

About this neuroscience research

The study was conducted together with Professor Duk-Hee Lee, Kyungpook National University, Daegu, Korea, Professor Bert van Bavel and Samira Salihovic, PhD, Örebro University, Professor David Jacobs, University of Minnesota, Minneapolis, and Monica Lind, Associate Professor in Environmental Medicine at the Department of Occupational and Environmental Medicine, Uppsala University Hospital.

Funding: The study has been funded by Formas and the Swedish Research Council.

Source: Lars Lind – Uppsala Univesity
Image Credit: The image is credited to the CDC and is in the public domain.
Original Research: Abstract for “Association between background exposure to organochlorine pesticides and the risk of cognitive impairment: A prospective study that accounts for weight change” by Duk-Hee Lee, P. Monica Lind, David R. Jacobs Jr., Samira Salihovic, Bert van Bavel, and Lars Lind in Environment International. Published online February 13 2016 doi:10.1016/j.envint.2016.02.001


Abstract

Association between background exposure to organochlorine pesticides and the risk of cognitive impairment: A prospective study that accounts for weight change

Background

Background exposure to organochlorine (OC) pesticides was recently linked to cognitive impairment and dementia in cross-sectional and case–control studies. This prospective study was performed to evaluate if OC pesticides at baseline are associated with the future risk of cognitive impairment in elderly, with particular focus on weight change.

Methods

Plasma concentrations of 3 OC pesticides (p,p′-DDE, trans-nonachlor, and hexachlorobenzene) were measured among 989 men and women aged 70 years in the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS). Cognitive impairment was validated by reviewing medical records. During the ten year follow-up, cognitive impairment was developed in 75 subjects. When weight change from age 70 to 75 was considered in analyses, elderly with incident cases before age 75 were excluded to keep the prospective perspective, leaving 795 study subjects and 44 incident cases.

Results

The summary measure of 3 OC pesticides predicted the development of cognitive impairment after adjusting for covariates, including weight change. Compared to subjects with OC pesticides < 25th percentile, adjusted hazard ratios (HRs) in those with 25th–<75th and ≥ 75th percentiles were 3.5 (95% confidence interval: 1.5–8.5) and 3.2 (1.1–7.6), respectively (Ptrend = 0.04). Among 506 subjects who maintained or gained body weight, adjusted HRs were 6.9 and 11.6 (1.4–92.6) among the elderly in the 25th–<75th and ≥ 75th percentiles compared to < 25th percentile (Ptrend < 0.01).

Conclusions

This prospective study demonstrates that background exposure to OC pesticides are linked to the risk of developing cognitive impairment in elderly. The role of the chronic exposure to low dose OC pesticides in the development of dementia should be further evaluated in other populations.

“Association between background exposure to organochlorine pesticides and the risk of cognitive impairment: A prospective study that accounts for weight change” by Duk-Hee Lee, P. Monica Lind, David R. Jacobs Jr., Samira Salihovic, Bert van Bavel, and Lars Lind in Environment International. Published online February 13 2016 doi:10.1016/j.envint.2016.02.001

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