Infectious burden and cognitive function: the Northern Manhattan Study.

OBJECTIVE

We hypothesized that infectious burden (IB), a composite serologic measure of exposure to common pathogens (i.e., Chlamydia pneumoniae, Helicobacter pylori, cytomegalovirus, and herpes simplex virus 1 and 2) associated with vascular risk in the prospective Northern Manhattan Study (NOMAS), would also be associated with cognition.

METHODS

Cognition was assessed using the Mini-Mental State Examination (MMSE) at enrollment and the modified Telephone Interview for Cognitive Status (TICS-m) at annual follow-up visits. Adjusted linear and logistic regressions were used to measure the association between IB index and MMSE. Generalized estimating equation models were used to evaluate associations with TICS-m and its change over time.

RESULTS

Serologies and cognitive assessments were available in 1,625 participants of the NOMAS cohort. In unadjusted analyses, higher IB index was associated with worse cognition (change per standard deviation [SD] of IB for MMSE was -0.77, p < 0.0001, and for first measurements of TICS-m was -1.89, p < 0.0001). These effects were attenuated after adjusting for risk factors (for MMSE adjusted change per SD of IB = -0.17, p = 0.06, for TICS-m adjusted change per SD IB = -0.68, p < 0.0001). IB was associated with MMSE ≤24 (compared to MMSE >24, adjusted odds ratio 1.26 per SD of IB, 95% confidence interval 1.06-1.51). IB was not associated with cognitive decline over time. The results were similar when IB was limited to viral serologies only.

CONCLUSION

A measure of IB associated with stroke risk and atherosclerosis was independently associated with cognitive performance in this multiethnic cohort. Past infections may contribute to cognitive impairment.