Seropositivity for toxocariasis is associated with worse cognitive functioning in older adults: The national health and nutrition examination survey 2011 to 2014

Abstract

Abstract Background Toxocariasis is an important broad-spectrum zoonotic parasite linked with poorer cognitive functioning in animals. However, this relationship is rarely studied in humans. Method A total of 3,188 older adults aged 60 and above from the National Health and Nutrition Examination Survey 2011 to 2014 were included. IgG antibody against Toxocara sapp. was tested by a Luminex assay using recombinant rTc-CTL-1 antigen. A value > 23.1 mean fluorescence intensity (MFI) indicated positive for toxocariasis, ≤ 23.1 MFI as negative. The Consortium to Establish a Registry for Alzheimer’s Disease Word Learning subtest (CERAD-WL) immediate and delayed memory, the Animal Fluency test (AFT), and the Digit Symbol Substitution Test (DSST) were used to assess cognitive functioning. Cognitive test-specific and global cognitive z scores were computed using means and standard deviations. Multivariate linear regression models were constructed to examine the association between toxocariasis and each cognitive test-specific and global cognitive standardized z score. All models were controlled for age, race/ethnicity, education, depressive symptoms, smoking status, body mass index (BMI), prevalent coronary heart disease, stroke, and systolic blood pressure. Results Most of the 3188 participants (mean age 70.0) were female (51.3%), non-Hispanic White (47.1%), and completed some college or above (48.1%). A total of 288 participants were seropositive for toxocariasis (9.0%). Adjusted linear regression showed that compared with participants with negative toxocariasis, those with positive toxocariasis had a lower CERAD W-L immediate recall (beta [β] -0.19, 95% Confidence interval [CI] -0.32, -0.06), AFT (β -0.16, 95% CI -0.29, -0.03), DSST (β -0.22, 95% CI -0.36, -0.09) as well as global cognition (β -0.20, 95% CI -0.33, -0.06) standardized z scores after controlling for covariates. Discussions In our study, seropositive toxocariasis was significantly associated with test-specific and global cognition in older adults. Public health measures to prevent human toxocariasis might help protect older adults’ cognitive function.