Inflammatory mechanisms underlying the effects of everyday discrimination on age-related memory decline

Abstract

BACKGROUND/OBJECTIVES: Previous research suggests that everyday discrimination is associated with worse episodic memory and partially mediates Black-White disparities in memory aging. The biological mechanisms underlying the link between everyday discrimination and memory are unclear but may involve inflammatory processes. This study aimed to determine whether systemic inflammation, indexed by blood levels of C-Reactive Protein (CRP), mediates associations between everyday discrimination and episodic memory over six years. DESIGN: A longitudinal mediation model quantified associations between baseline everyday discrimination, four-year change in CRP, and six-year change in episodic memory. SETTING: The Health and Retirement Study (HRS). PARTICIPANTS: 12,624 HRS participants aged 51 and older. MEASUREMENTS: Everyday Discrimination Scale, high-sensitivity CRP assays of dried blood spots, composite scores of immediate and delayed recall of a word list. RESULTS: Black participants reported greater everyday discrimination. Greater discrimination was associated with lower baseline memory and faster memory decline. Higher CRP at baseline partially mediated the negative association between discrimination and baseline memory, but CRP change did not mediate the association between discrimination and memory decline. CONCLUSION: This U.S.-representative longitudinal study provides evidence for deleterious effects of discrimination on subsequent episodic memory. The fact that elevated CRP only partially explained the concurrent association between discrimination and memory highlights the need for more comprehensive investigations of biological mechanisms underlying the link between social stress and age-related memory decline in order to better characterize potential intervention targets to reduce racial inequalities in memory aging.

Social Relationships and Adaptation in Later Life

“…Similarly, Zahodne and colleagues ( Zahodne et al., 2019a ), using longitudinal data from a U.S. nationally representative sample of older adults, found that more contact was associated with better memory at baseline and slower memory decline over 6 years. On the other hand, social network size was not associated with memory trajectories ( Zahodne et al., 2019c , Zahodne et al., 2019b , Zahodne et al., 2019a ). These findings suggest that it is the stimulation of social contact rather than the number of social ties which positively affects cognitive functioning among older people.…”

“…For example, in a cross-sectional study of Chinese nonagenarians and centenarians, the number of friends and being married, but not the number of children or ties with neighbors, were associated with better cognitive health ( Wang et al., 2015 ). Finally, in a recent longitudinal nationally representative study of U.S. older adults, more frequent contact with friends, but not family, was associated with less decline in memory over time ( Zahodne et al., 2019a , Zahodne et al., 2019b , Zahodne et al., 2019c ).…”

“…An examination of the influence of early parental relationship quality on cognitive health outcomes by Sharifian and colleagues ( Sharifian et al., 2019 ) revealed that respondents from a nationally representative U.S. sample of older adults who reported higher retrospective maternal relationship quality showed less decline in episodic memory over time through reduced loneliness and depressive symptoms. Similarly, in a population-based longitudinal study of non-Hispanic African American and White adults, greater retrospective childhood social support was associated with better initial memory through educational attainment and mental (stress) and physical (BMI) health pathways ( Zahodne et al., 2019c , Zahodne et al., 2019b , Zahodne et al., 2019a ). These findings highlight the enduring effects of early life social relationships on health-related outcomes directly and indirectly through multiple biopsychosocial pathways.…”

“…These authors also examined the reverse, to see whether memory was associated with changes in social contact over the same span of time. It is noteworthy that they report no association between memory and change in contact frequency ( Zahodne et al., 2019c , Zahodne et al., 2019b , Zahodne et al., 2019a ), indicating that it is the loss of social relations that is detrimental to cognitive health, rather than declines in cognitive health leading to more isolation.…”

“…In a recent longitudinal study of social activities among Chinese older adults, an independent association emerged between loneliness and global cognitive decline over 9 years, among those engaging in more frequent social activities ( Zhong et al., 2017 ). Loneliness has also been associated with increased inflammation, important as inflammation is often associated with all of the aforementioned health outcomes ( Kiecolt-Glaser et al., 2010 ), including cognitive function ( Zahodne et al., 2019b ). Increased inflammation is one of the mechanisms proposed by Hawkley and Capitanio (2015) , as to how loneliness affects health.…”