Abstract
Background:
Serological evidence of the burden of common infections (IB=infectious burden) has been associated with stroke, carotid atherosclerosis, and global cognitive function in the race/ethnically diverse community-based Northern Manhattan Study (NOMAS) cohort. We hypothesized that IB is associated with worse performance and decline on a battery of neuropsychological tests.
Methods:
A subsample of stroke-free NOMAS participants underwent a neuropsychological battery, and a subsample of these had repeated testing a mean of six (SD=2) years later. Using factor analysis-derived domain-specific Z scores for memory, language, executive function, and processing speed, we examined associations between a quantitative IB index previously associated with stroke risk and based on five common infections (Chlamydia pneumoniae, Helicobacter pylori, cytomegalovirus, and herpes simplex viruses 1 and 2) and cognitive performance in each domain. We used multivariable linear regression and adjusted for age, sex, education, race/ethnicity, insurance status, diabetes, hypertension, hypercholesterolemia, BMI, moderate alcohol, moderate-heavy physical activity, and smoking.
Results:
There were 588 NOMAS participants with IB index and cognitive data (mean age=71, 62%women, 14% white, 16% black, 70% Hispanic) and 287 with repeat cognitive testing. After adjusting for demographic variables, IB index was inversely associated with all cognitive domains, although not all associations were significant (executive function, beta=-0.11, p=0.002; language, beta=-0.07, p=0.04; memory, beta=-0.06, p=0.11; processing speed, beta=-0.07, p=0.07). These effects attenuated only slightly after adjusting for vascular risk factors. The IB index associated with cognitive decline across domains, but a trend toward significance existed only for memory, after adjusting for baseline performance, demographic and vascular risk factors (beta=-0.09, p=0.07).
Conclusions:
A quantitative measure of IB associated with stroke risk was inversely associated with executive function and language, and decline in memory performance. Past exposure to common infections may contribute to vascular cognitive impairment and warrant further study.