Dietary Inflammatory Index, inflammation and cognitive decline in older adults: The Health ABC Study

Background: Inflammation is implicated in the pathogenesis of Alzheimer’s disease and progression of age-related neurodegeneration. Diet is known to modulate systemic inflammation. For example, fruit and vegetables have anti-inflammatory effects and saturated fat has pro-inflammatory effects. Few studies to date have investigated inflammatory dietary factors in relation to cognitive decline. The dietary Inflammatory Index (DIITM) is an empirically derived score that reflects inflammatory potential of the diet. We examined associations between DII scores, inflammatory biomarkers and longitudinal cognitive decline in the HealthABC Study.
Methods: Baseline energy-adjusted DII (E-DII) scores were computed from food frequency questionnaire data on 2,429 non-demented adults, aged 74 ± 2.8 (range 69.3 to 80.9) years. Higher E-DII scores indicated greater pro-inflammatory dietary potential. Inflammatory biomarkers (CRP and IL-6) also were measured at baseline. Cognitive decline was assessed using repeated Modified Mini Mental State Examination (3MS) and Digit Symbol Substitution Test (DSST) scores over a 9-year follow-up period. Linear mixed models were used to examine the association between E-DII and trajectory of cognitive decline.
Results: Mean E-DII was -2.39 ±1.70 (range -5.49 to +2.90). In multivariable models, participants in the highest E-DII tertile (more pro-inflammatory diet) had significantly increased mean CRP levels compared to the middle and lowest tertiles (3.13 vs 2.77 and 2.64 ug/ml) and mean IL-6 levels (2.66 vs 2.48 and 2.44 pg/ml) (PTrend = 0.01 and PTrend = 0.05, respectively). Over a median 9 years of follow-up (range 1.9 to 9.5 years) we found no significant association between DII and rate of cognitive decline on the 3MS (p = 0.28) or DSST (p = 0.16).
Conclusion: In older adults, a more pro-inflammatory diet as measured using the DII, is associated with increased inflammatory biomarkers but not with rate of cognitive decline during 9 years of follow-up.