Accumulation of affective symptoms and midlife cognitive function: the role of inflammation

Background: The aim of the present study was to test whether C-Reactive Protein (CRP), a proxy measure of inflammation, is elevated in people with higher child and adulthood affective symptoms and whether elevated CRP predicts midlife cognitive function. Methods: Data were used from the National Child Development Study (n = 6276). Measures of memory, verbal fluency, information processing speed and accuracy were available in midlife (age 50). Affective symptoms were assessed in childhood (ages 7, 11, 16) and in adulthood (ages 23, 33, 42, 50). The level of plasma CRP was measured at age 44. Pathway models, unadjusted and fully adjusted for sex, education, childhood socioeconomic position, childhood cognitive ability and affective symptoms at age 50, were fitted to test direct associations between affective symptoms and midlife cognitive function, and indirect associations via the inflammatory pathway (CRP level). Results: In a fully adjusted model, there were significant indirect associations between adult affective symptoms and immediate memory (ß=-0.01, SE=0.003, p=.03) and delayed memory (ß=-0.01, SE=0.004, p=.03) via CRP. In addition, there were significant indirect associations between affective symptoms in childhood and immediate memory (ß=-0.001, SE=0.00, p=.03) and delayed memory (ß=-0.001, SE=0.001, p=.03), via adult affective symptoms and associated CRP. Independent of CRP, there was a significant direct association between adult affective symptoms and information processing errors (ß=0.47, SE=0.21, p=.02). There were no direct or indirect associations between affective symptoms and verbal fluency or information processing speed. Conclusions: CRP at age 44 is elevated in people with higher affective symptoms from age 7 to 42, and elevated CRP is associated with poorer immediate and delayed memory at age 50.