Introduction

Exposure to infectious diseases has been linked to decreases in cognition (Gale et al., 2016). Cytomegalovirus (CMV) is one such disease. CMV is a human herpes virus which, once contracted, remains in the body until death (Cannon, Schmid, & Hyde, 2010). Interestingly, CMV can reactivate after remaining dormant in a person for several years. Once a person has contracted CMV which may lead to a mild illness with symptoms such as fever, sore throat, fatigue, and swollen glands. In some cases, CMV can cause mononucleosis or hepatitis (Centers for Disease Control and Prevention, 2016). CMV is contracted through the sharing of bodily fluids, including urine, saliva, blood, tears, semen, and breast milk. Women who carry CMV may pass it to their children during pregnancy. Congenital CMV can cause sensorineural hearing loss or other neurological impairments (Cannon, Schmid, & Hyde, 2010). For both children and adults, most people are unaware that they are infected as most infections or reactivations of the disease are asymptomatic (Pass et al., 2009). The most reliable way to diagnose CMV is through testing blood serum (Cannon, Schmid, & Hyde, 2010). The seroprevalence of CMV in the US is as high as 59%, with increasing prevalence associated with age (Staras et al., 2006). 
In older adults, CMV has been linked to increased rates of cognitive decline over a four-year period (Aiello et al., 2006). Specifically, an increased amount of CMV antibodies were associated with significant declines on the Modified Mini-Mental State Examination, indicating that blood serum levels of CMV are associated with increased rates of global cognitive decline. Other analyses have demonstrated that CMV and other herpesviruses have been linked to cognitive decline across the lifespan (Tarter, Simanek, Dowd, & Aiello, 2013). CMV has been treated as a continuous variable (using antibody estimates to estimate CMV exposure) and as a discrete variable, whether an individual is positive or negative for CMV on a blood test. Older adults who were seropositive for CMV demonstrated declines in several cognitive domains including immediate memory, delayed memory, and reaction time compared to seronegative individuals (Tarter, Simanek, Dowd, & Aiello, 2013). Other global measures have examined the effect of toxic disease burdens effect on cognition, which has indicated that toxic diseases are related to decreases in learning, memory, and processing speed (Gale et al., 2016). 
To date, no study has examined the link between CMV seropositivity and brain imaging in older adults. This study seeks to determine whether CMV seropositivity in older adults is related to decreased cortical thickness.

Methods

Participants

Participants were recruited at Brigham Young University from October of 2014 through November of 2015. Participants were screened for MRI compatibility. The participants used in this study were a subset of the data, and only include those participants over 50 years old. Twenty-five participants were included in the study with an average age of 71.5. This sample includes 12 males and 13 females. All participants completed a neuropsychological testing battery (that included measures of memory, executive function, attention, and personality), received blood draws screening for the presence of an infectious disease, and completed an MRI scan. See Table 1 for a summary of demographic information.