Table 1.
Summary of Studies Examining Inflammatory Biomarkers in Relation to Cognitive Function
| Study | Design | Population | Participant Age Range (Mean) | Cognitive Measures | Inflammatory Measures | Stratification of Assays | Results |
|---|---|---|---|---|---|---|---|
| Wright et al., 2006 | Cross- sectional | N ≤ 269 Northern Manhattan Study, stroke- free cohort | 40+ (67) | MMSE (log transformed) | IL-1, IL-2, IL-6, TNF-α, IL-2R TNFR-1, TNFR- 2, & CRP | Continuous and Tertiles | IL-6 negatively associated with MMSE |
| Baune et al., 2008 | Cross- sectional | N = 369 MEMO Study (Germany) | 65+ (73) | Memory, Attention, Cognitive Speed, Motor Function | IL-1β, sIL-4R, IL-6, IL-8, IL- 10, IL-12, & TNF-α | Continuous | IL-8 negatively associated with Memory, Speed, and Motor Function |
| Ravaglia et al., 2003 | Cross- sectional | N = 744 Conselice Study (Italy) | 65–93 (73) | Executive Function/Visuo- spatial (Clock Drawing Test) | CRP | Dichotomized | CRP levels negatively associated with Clock Drawing Test performance |
| Teunissen et al., 2003 | Prospective with six-year follow-up | N ≤ 92 Maastricht Aging Study (Netherlands) | 30–82 (57) | Learning/ Encoding, Memory, Attention, Cognitive Speed | IL-6, Haptoglobin, & CRP | Continuous | Haptoglobin negatively associated with Speed/Attention and Memory; CRP negatively associated with Learning and Memory |
| Dik et al., 2005 | Prospective with three-year follow-up | N = 1,284 Longitudinal Aging Study (Amsterdam) | 62–85 (75) | Processing Speed, Memory, Fluid Intelligence, MMSE | ACT, CRP, & IL-6 | Tertiles (ACT & CRP) Dichotomized (IL-6) | ACT associated with baseline Delayed Recall and Highest ACT tertile associated with increased risk of decline on MMSE |
| Yaffe et al., 2003 | Prospective with two-year follow-up | N = 3,031 Health ABC Study (black and white elders) | 70–79 (74) | 3MS | CRP, IL-6, & TNF-α | Tertiles | Highest tertiles of IL-6 and CRP associated with poorer 3MS performance at baseline and follow-up with 24% increase in risk of cognitive decline over two years, relative to lowest tertiles; No interaction with race |
| Yaffe, Fiocco, et al., 2009 | Prospective with eight-year follow-up | N = 2,509 Health ABC Study (black and white elders) | 70–79 (74) | 3MS | CRP, IL-6, & TNF-α | Continuous, log- transformed | Lower levels of CRP & IL-6 associated with stable cog function over eight years |
| Alley et al., 2008 | Prospective with seven-year follow-up | N = 851 MacArthur Study of Successful Aging, subsampled from Established Populations for Epidemiologic Studies of the Elderly for age 70+ | 70+ (74 at baseline) | Abstraction Verbal Recall Language Spatial Ability Spatial Recog. Summary Score Mental Status | CRP IL-6 | Tertiles, then dichotomized into high-risk categories in subsequent analyses | Baseline levels of CRP & IL-6 negatively associated with cognitive function (abstraction, language & summary score); highest tertile of IL-6 had greatest risk of decline |
Notes. 3MS = Modified Mini-Mental State Examination; ACT = Antichymotrypsin; CRP = C-reactive protein; IL = Interleukin; ILR = Interleukin receptor; MMSE = Mini-Mental State Examination; TNF-α = Tumor necrosis factor-alpha; TNFR = Tumor necrosis factor receptor.