Organochlorine pesticides and late life cognitive function: does race/ethnicity and sex matter?

Abstract Background Organochlorines (OCs) pesticides persist in the environment and body for extended periods. Little is known about their long‐term impact on cognition in later life. Some studies, have shown higher levels of selected OCs associated with lower cognitive function (CF). It remains unclear if the association differs among racial/ethnic groups or by sex. Method Using weighted linear generalized estimating equations, we explored whether the association between seven log‐transformed lipid‐adjusted OCs (ng/g) and CF is modified by race/ethnicity and sex in 985 adults, age 60+ from the National Health and Nutrition Examination Surveys (2011‐2014). Sample included: 57% females; 78.8% Non‐Hispanic (NH) White; 9.2% NH‐Black; 3.6% Mexican‐American; 4.1% Other‐Hispanic; 3.7% NH‐Asian; 0.5% Other Race/Ethnicity. A composite CF score was created using the mean of the z‐scores for word‐list memory test (CERAD W‐L) which included delayed recall and word list learning, animal fluency, and the Digit Symbol Substitution test (DSST). Covariates included age, education, marital status, sex, race/ethnicity. Sensitivity analysis included: BMI, Ratio of Income‐to‐Poverty (IPR) categorized in tertiles, and longest occupation held. Result Adjusting for covariates, lower composite‐CF was associated with higher levels of p,p’‐DDT ( p = 0.040). This remained significant after adjusting for BMI ( p = 0.045), but not when accounting for IPR ( p = 0.117) or longest held occupation ( p = 0.083). For specific CF tests, beta‐hexachlorocyclohexane, hexachlorobenzene, mirex, oxychlordane, p’p‐DDE, p’p‐DDT, and trans‐nonachlor were all associated with lower scores on DSST ( p‐range = 0.03‐0.001). None of the associations differed by race/ethnicity. But a few differed by sex. After sex‐stratification, lower DSST scores were associated with higher levels of hexachlorobenzene in women ( p = 0.032], but not men ( p = 0.242). In sensitivity analyses, hexachlorobenzene lost all statistical significance after adjusting for each additional variable. The association between mirex and DSST disappeared after adjusting for longest occupation ( p = 0.068). All other specific‐OC associations remained significant after BMI, IPR and occupation adjustment ( p< 0.05). Conclusion Higher blood levels of some OCs were associated with lower CF among older adults, some particularly affecting women, suggesting there may be long term negative effects of these chemicals. Future exposure studies should focus on sex‐differences. These associations did not differ between races; thus future analyses should consider examining within race/ethnic differences.