Dietary inflammatory index scores and cognitive aging: results from the Framingham heart Study offspring cohort

Nutritional factors can abet or protect against systemic chronic inflammation, which plays an important role in the development and progression of dementia. We evaluated whether higher (i.e. pro-inflammatory) Dietary Inflammatory Index (DII) scores were associated with cognitive decline in the community-based Offspring Framingham Heart Study (FHS).

1,614 older adults (mean age 61 years [standard deviation (SD)], 9;55% women]) completed validated 126-item Food Frequency Questionnaires (FFQ), administered at FHS examination cycle 7 (1998-2001) and examination cycle 5 (1991-1995) and/or 6 (1995-1998). We created a DII score (based on the published method by Shivappa et al. 2014) for each available exam; a cumulative DII score was calculated by averaging exam-specific scores across the two or three exams. Cognitive testing was completed at call back sessions following examination cycles 7 and 8 (2005-2008). Exam 7 was considered as study baseline and participants were followed over a mean time of seven years (SD 1). We excluded participants with prevalent dementia at baseline and those with no cognitive testing data at either/or exams 7 and 8. We examined associations between the cumulative DII score and cognitive test scores over time using annualized change adjusting for age, sex, education (model 1) and additionally for exam 7 measures of body mass index, total energy intake, total cholesterol: high-density lipoprotein ratio, smoking and anti-cholesterol medication (model 2).

Higher DII scores were significantly associated with (less) decline in performance on Similarities (verbal comprehension/reasoning) and Global cognition, following adjustments for model 1 covariates (Model 1:β and SE, 0.017, 0.008,p=0.03; 0.004,0.002,p=0.02, respectively). The effect sizes remained similar after additional adjustment for Model 2 covariates (0.018, 0.009,p=0.06; 0.004, 0.002,p=0.03, respectively). Additionally, we found that higher DII scores associated with accelerated decline in performance on Trail Making B-A (processing speed and executive function) (Model 2: -0.010, 0.004,p=0.03). We observed no relationships between higher DII scores and other neuropsychological tests. Further, stratified analyses revealed a linear relationship between higher DII scores and (less) decline in performance on Hooper visual organization among men, but not women (Model 2: 0.022, 0.010,p=0.02; -0.011, 0.009,p=0.23, respectively).

Higher DII scores were associated with (less) cognitive decline. We take our unexpected findings with caution as we previous have seen a relationship between higher DII scores and increased risk for dementia. To date, such studies have been very limited, most studies that found a relationship were cross-sectional and have used less sensitive testing. Future longitudinal studies with sensitive neuropsychological test measures are encouraged to elucidate whether a longitudinal relationship between higher DII scores and age-related cognitive decline exists.