Long-term diet quality and its change in relation to late-life subjective cognitive decline

Background Evidence regarding the role of diet quality, especially its change, in subjective cognitive decline (SCD) is scarce. Objectives To examine associations of long-term diet qualities, including Alternate Mediterranean Diet (AMED), Dietary Approaches to Stop Hypertension (DASH), and Alternate Healthy Eating Index 2010 (AHEI-2010) with SCD in the Nurses' Health Study. Methods We followed 49,493 female registered nurses averaged 48 years from 1984 to 2014. Diet scores were derived from seven repeated food frequency questionnaires in 1984, 1986, and every four years afterward until 2006. Self-reported SCD was assessed in 2012 and 2014 by a 7-item questionnaire on memory and cognition changes. Categorical SCD score was classified as "none" (0 points, 40.8%), "moderate" (0.5-2.5 points, 46.9%), and "severe" (3-7 points, 12.3%). Results Multinomial and linear regression models were adjusted for total calorie, demographic characteristics, major lifestyle, and clinical factors. Comparing top vs. bottom quintiles of AMED, DASH, and AHEI-2010, multivariable-adjusted odds ratios (ORs) (95% confidence intervals, CIs) for severe vs. none SCD were 0.57 (0.51, 0.64), 0.61 (0.55, 0.68), and 0.81 (0.73, 0.90), respectively. Similar associations remained for three diet indices evaluated 28 years before SCD assessment. Compared to participants with lowest diet quality tertiles in both remote and recent years, the lowest odds of severe SCD was observed among those who maintained highest diet quality tertiles over time, with a 40%, 32%, and 20% lower odds of severe SCD for AMED, DASH, and AHEI-2010, respectively. Moreover, the odds of severe SCD was lower among those with improved diets over time; for each standard deviation higher in diet quality change, reduced risks were 11% for AMED, 5% for DASH, and 3% for AHEI-2010, respectively. Conclusion Our findings support beneficial roles of long-term adherence to, and improvement in healthy dietary patterns for maintenance of subjective cognition in women.