Toxoplasma gondii seropositivity and cognitive functioning in older adults: The national health and nutrition examination survey 2011 to 2014

Abstract

Abstract Objective To examine the relationship between Toxoplasma gondii infection and cognitive functioning in older adults. Method A total of 2,956 older adults aged 60 and above from the National Health and Nutrition Examination Survey from 2011 to 2014 were included. Serum toxoplasma gondii antibody was analyzed in the lab. A value > 33 IU/mL was categorized as positive for toxoplasma gondii infection; <27 IU/mL was categorized as negative. Cognitive tests included 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). Multivariate linear regression models were constructed to examine the association between toxoplasma gondii seropositivity and standardized cognitive test-specific and global cognition z scores. All models were adjusted for age, race/ethnicity, education, depressive symptoms, smoking status, body mass index, prevalent coronary heart disease, stroke, and systolic blood pressure. Results Most of the 2,956 participants (mean age 70.0) were female (51.0%), non-Hispanic White (48.3%), and completed some college or above (48.3%). A total of 703 participants were positive for toxoplasma gondii infection (23.8%). Adjusted linear regression showed that compared with participants with negative toxoplasma gondii infection, those with positive toxoplasma gondii infection had lower CERAD-WL immediate memory (beta [β] -0.16, 95% confidence interval [CI] -0.25,-0.07), CERAD-WL delayed memory (β -0.15, 95% CI -0.24,-0.06), AFT (β -0.15, 95% CI -0.24,-0.06), DSST (β -0.34, 95% CI -0.43,-0.26), and global cognition (β -0.24, 95% CI -0.32,-0.16) z scores after controlling for the covariates. Conclusions Toxoplasma gondii seropositivity is independently associated with worse immediate and delayed verbal learning, language proficiency, executive functioning, processing speed, sustained attention, working memory, as well as global cognition in older adults. Public health measures are needed to prevent toxoplasma gondii infection, which may help preserve cognitive functioning in older adults.