Chronic systemic inflammation has been associated with both age-related cognitive decline and depression, leading researchers to study it further.
Jordan Weiss, a PhD candidate in demography and Healthy Brain Scholar at the University of Pennsylvania, co-authored two studies with collaborators from the National Institute on Aging that examined associations between systemic inflammation, Alzheimer’s disease (AD), and depression. One study examined cytokines and their relation to cognitive health, and the other study examined the association between systemic inflammation and depression.
Both studies used data from the longitudinal Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study which surveyed more than 3,000 urban adults aged 30-64 living in Baltimore city, MD. HANDLS participants come from a wide range of socioeconomic circumstances, allowing for the investigation of health disparities across age, sex, race, and socioeconomic and neighborhood circumstances.
Small proteins released by cells called cytokines have been associated with AD. Certain cytokines contribute to nerve injury and inflammation, and chronic systemic inflammation has been related to early markers of cognitive decline.
The types of cytokines known to be related to AD were analyzed for their potential associations with cognitive function. Participants varied across age, sex and race, and the results differed among the groups. For example, one cytokine was linked to a faster rate of decline when testing executive functioning for adults aged 50 years and older, whereas another cytokine was linked to poorer attention in those aged 50 and younger.
Systemic inflammation might also affect depressive symptoms over time. Participants were examined using the Center for Epidemiologic Studies-Depression scale. The scale measures physical symptoms such as pain, fatigue or dizziness, mood, and interpersonal problems. The findings suggest that systemic inflammation is directly linked to depressive symptoms and impacts participants differently across race and sex.
These studies provided further evidence in the link between systemic inflammation, cognitive decline and depression. The authors of each study argue that more research be done on systemic inflammation as well as relevant biological and psychosocial factors to understand the impact of systemic inflammation on cognition.
“There is a growing need to understand social and health disparities in aging, and how biopsychosocial factors over the life course may shape them,” said Weiss.
The HANDLS study is unique in its sampling of a racially diverse urban adult population which allows for the investigation of potential pathways through which these disparities may emerge.
“Although we identified heterogeneous effects of systemic inflammation on health outcomes across racial groups, we have yet to explore the mechanisms,” Weiss said. “Stress, considered a top 10 contributor to health disparities, is a plausible candidate known to be a precursor of inflammation and vary across social and racial groups.”
Weiss believes that future observational and intervention studies investigating the links between stress, systemic inflammation, and cognitive and mental wealth are warranted.