Association of Dietary Patterns in Midlife and Cognitive Function in Later Life in US Adults Without Dementia

IMPORTANCE: The association of dietary patterns, or the combinations of different foods that people eat, with cognitive change and dementia is unclear. OBJECTIVE: To examine the association of dietary patterns in midlife with cognitive function in later life in a US population without dementia. DESIGN, SETTING, AND PARTICIPANTS: Observational cohort study with analysis of data collected from 1987 to 2017. Analysis was completed in January to February 2019. Community-dwelling black and white men and women from Washington County, Maryland; Forsyth County, North Carolina; Jackson, Mississippi; and suburban Minneapolis, Minnesota, participating in the Atherosclerosis Risk in Communities (ARIC) study were included. EXPOSURES: Two dietary pattern scores were derived from a 66-item food frequency questionnaire using principal component analysis. A Western, or unhealthy, dietary pattern was characterized by higher consumption of meats and fried foods. A so-called prudent, or healthier, dietary pattern was characterized by higher amounts of fruits and vegetables. MAIN OUTCOMES AND MEASURES: Results of 3 cognitive tests (Digit Symbol Substitution Test, Word Fluency Test, and Delayed Word Recall) performed at 3 points (1990-1992, 1996-1998, and 2011-2013) were standardized and combined to represent global cognitive function. The 20-year change in cognitive function was determined by tertile of diet pattern score using mixed-effect models. The risk of incident dementia was also determined by tertile of the diet pattern score. RESULTS: A total of 13 588 participants (7588 [55.8%] women) with a mean (SD) age of 54.6 (5.7) years at baseline were included; participants in the top third of Western and prudent diet pattern scores were considered adherent to the respective diet. Cognitive scores at baseline were lower in participants with a Western diet (z score for tertile 3 [T3], −0.17 [95% CI, −0.20 to −0.14] vs T1, 0.17 [95% CI, 0.14-0.20]) and higher in participants with a prudent diet (z score for T3, −0.09 [95% CI, −0.12 to −0.06] vs T1, −0.09 [95% −0.12 to −0.06]). Estimated 20-year change in global cognitive function did not differ by dietary pattern (difference of change in z score for Western diet, T3 vs T1: −0.01 [95% CI, −0.05 to 0.04]; and difference of change in z score for prudent diet, T3 vs T1: 0.02 [95% CI, −0.02 to 0.06]). The risk of incident dementia did not differ by dietary pattern (Western hazard ratio for T3 vs T1, 1.06 [95% CI, 0.92-1.22]; prudent hazard ratio for T3 vs T1, 0.99 [95% CI, 0.88-1.12]). CONCLUSIONS AND RELEVANCE: This study found that the dietary pattern of US adults at midlife was not associated with processing speed, word fluency, memory, or incident dementia in later life.