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Background: Cognitive impairment is common among older adults with diabetes mellitus (DM). This study aimed to examine the associations between DM with/without diabetic retinopathy (DR) and adverse cognitive outcomes in older adults, and to assess the potential role of the dietary inflammatory profile in these associations. Methods: This observational study included older adults from the National Health and Nutrition Examination Survey (NHANES), UK Biobank (UKB), and the Wenzhou dataset. Cognitive outcomes were assessed using cognitive tests in NHANES and the Wenzhou dataset, and by all-cause dementia identified from ICD-10 codes in UKB, respectively. Dietary inflammatory index (DII) scores were derived from 24-h dietary recalls in NHANES, the Oxford WebQ in UKB, and the FFQ-25 in the Wenzhou dataset, respectively. Weighted multivariable-adjusted Poisson regression, robust Cox proportional hazards regression and conditional logistic regression were used in NHANES, UKB and the Wenzhou dataset, respectively. Exploratory mediation analyses were conducted in all three datasets to assess the potential role of DII in the associations between DM with or without DR and cognitive outcomes. Results: In NHANES, poorer cognitive performance was associated with DM and higher DII in the overall sample, while poorer cognitive performance was associated with DR and higher DII among participants with DM. Exploratory mediation analyses in NHANES suggested a potential role of DII in the associations between DM with/without DR and cognitive function impairment (CFI) (DM: 15.0% mediated; DR: 8.0% mediated). Restricted cubic spline analysis showed that higher DII levels were associated with higher odds of CFI. In UKB and the Wenzhou dataset, exploratory mediation analyses showed significant indirect effects of DII in the association between DM and dementia (4.1% mediated) and between DR and cognitive impairment (13.6% mediated), respectively. Conclusion: Dietary inflammatory profile reflected by DII may play a potential role in the associations of DM with/without DR and cognitive dysfunction. Further prospective studies and randomized controlled trials are needed to clarify causality and potential clinical benefit.
Huang et al. (Tue,) studied this question.