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Temporal Cognitive Decline Associated with Exposure to Infectious Agents in a Population-based, Aging Cohort
Nimgaonkar VL, Yolken RH, Wang T, Chung-Chou HC, McClain L, McDade E, Snitz BE and Ganguli M
Alzheimers Disease & Associated Disorders, Published Online, 2015

Numerous cross-sectional studies have related exposure to neurotropic infectious agents with cognitive dysfunction in older adults, however, the temporal sequence is uncertain. In other words, does the infection precede the cognitive impairment?  Findings from a recent study conducted by Drs. Vishwajit Nimgaonkar, Mary Ganguli and their colleagues suggest that chronic viral infections could contribute to subtle cognitive dysfunctions even in apparently healthy older adults.  The study was conducted in collaboration with Dr. Robert Yolken of Johns Hopkins University.

In a representative, well-characterized, population-based aging cohort, the investigators determined whether the temporal trajectories of multiple cognitive domains are associated with exposure to cytomegalovirus (CMV), Herpes Simplex virus, type 1 (HSV-1), Herpes Simplex virus, type 2 (HSV-2), or Toxoplasma gondii (TOX). Complex attention, executive functions, memory, language, and visuospatial function were assessed annually for five years among consenting individuals. Study entry (baseline) IgG antibody titers indexing exposure to each infectious agent were examined by the investigators in relation to slopes of subsequent temporal cognitive decline using multiple linear regressions adjusted for potential confounders.

Drs. Nimgaonkar and Ganguli and their colleagues found that IgG levels for HSV-2 were significantly associated with baseline cognitive domain scores (N=1,022 participants). In addition, the IgG levels for HSV-2, TOX, and CMV, but not HSV-1, were significantly associated with greater temporal cognitive decline that varied by type of infection.   Results of this study indicate that exposure to CMV, HSV-2, or TOX is associated with cognitive deterioration in older individuals, independent of general age–related variables. Findings suggest the need for future research on the role of infectious agents in cognitive decline, which may ultimately lead to new methods for its prevention and treatment.

Contributors:
Vishwajit L. Nimgaonkar, MD, PhD, Lora McClain, BS, Beth E. Snitz, PhD and Mary Ganguli, MD (Department of Psychiatry, University of Pittsburgh School of Medicine)

Eric McDade, DO (Department of Neurology, University of Pittsburgh School of Medicine)

Tianxiu Wang, MS and Ho Chang Chung-Chou, PhD (Department of Biostatistics, Graduate School of Public Health, University of Pittsburgh)

Robert H. Yolken, MD, PhD (Department of Pediatrics, Johns Hopkins University School of Medicine)

This article appeared in the journal Alzheimer Disease & Associated Disorders.  To view the abstract, click here.