Threshold Effects of Total Copper Intake on Cognitive Function in US Older Adults and the Moderating Effect of Fat and Saturated Fatty Acid Intake.

Evidence for a relationship between total copper intake and cognition is lacking, and few studies have assessed the moderating effect of dietary fat and saturated fatty acid (SFA) intake on this relationship. Our aim was to explore the curvilinear association between total copper intake and cognitive function in older adults, and to clarify the moderating effect of dietary fat and SFA intake on the association. This was a cross-sectional analysis of data from National Health and Nutrition Examination Surveys 2011-2014. The analysis included 2,483 participants aged 60 years and older. Cognitive function was evaluated by the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Word Learning subtest, the Animal Fluency Test, and the Digit Symbol Substitution Test (DSST). Smooth curve fitting and two-piecewise linear regression models were performed to address the nonlinear association between total copper intake and cognitive function. Multivariable quadratic regression models and analyses stratified by total fat or SFA intake were used to assess the effects of the interaction between copper and fat intake and between copper and SFA intake on cognitive function. There was a nonlinear association between total copper intake and cognitive test scores. The inflection point of copper was 0.8 mg/d for the Consortium to Establish a Registry for Alzheimer's Disease Word Learning subtest and 1.4 mg/d for both the Animal Fluency test and the DSST. When copper intake was below the inflection point, positive associations were apparent for copper intake and Consortium to Establish a Registry for Alzheimer's Disease Word Learning subtest scores (β = 3.9; 95% CI 1.2 to 6.5), Animal Fluency test scores (β = 1.7, 95% CI .9 to 2.6), and DSST scores (β = 6.0, 95% CI 3.8 to 8.3). When copper intake was above the inflection point, a nonsignificant downward trend was found. Interactive effects between total copper and total fat intake (P interaction = .000) and between total copper and SFA intake (P interaction = .011) on the DSST scores were observed. In the low fat intake and low SFA intake groups, DSST scores first increased and then decreased with increasing copper. However, in the high fat intake and high SFA intake groups, DSST scores first increased and then flattened with increasing copper. The present study suggests a nonlinear association between copper intake and cognitive function and identifies threshold effects of copper intake on cognitive function. Copper intake below the inflection point was positively and independently associated with cognitive function. High fat and high SFA intake may protect older adults against a decline in DSST scores related to high copper intake.

Wang X ，Li X ，Xing Y ，Wang W ，Li S ，Zhang D ，Zheng W ，Shen X ... -  《Journal of the Academy of Nutrition and Dietetics》

Association of dietary ω-3 and ω-6 fatty acids intake with cognitive performance in older adults: National Health and nutrition examination Survey (NHANES) 2011-2014.

Dong X ，Li S ，Chen J ，Li Y ，Wu Y ，Zhang D ... -  《Nutrition Journal》

Oxidative Stress Mediates the Association Between Dietary Fat Intake and Cognition in US Older Adults.

Dietary fat intake was considered as a modifiable factor influencing cognitive performance. The objective was to 1) examine the associations between different types of dietary fat intakes and cognitive outcomes among elder adults (≥60 years old); 2) assess whether peripheral oxidative stress and antioxidant biomarkers are potential mediators of dietary fat intake and cognitive impairment relationship. Using data from National Health and Nutrition Examination Survey 2011-2014, total fat, saturated fatty acid (SFAT), monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA), cholesterol, ω-3 and ω-6 fatty acids were used to evaluate dietary fat intakes. Cognitive outcomes were assessed by word learning and recall modules from the consortium to establish a registry for Alzheimer's Disease (CERAD), animal fluency test, and digit symbol substitution test (DSST). Antioxidant biomarkers were assessed by gamma glutamyl transpeptidase (GGT), bilirubin, uric acid, and vitamin D levels. Linear regression models and causal mediation analysis were applied to quantify the associations. A total of 2,253 elder adults were included in the data analyses. Dietary intake of PUFA and ω-6 fatty acid were positively associated with DSST [β (95% CI): 0.06 (0.01,0.10), t statistic = 2.39, df= 2238, p = 0.02; β (95% CI): 0.06 (0.01,0.11), t statistic = 2.54, df= 2238, p = 0.01, respectively]. GGT was negatively associated with DSST [β (95% CI): -0.04 (-0.07, -0.01), t statistic = -2.73, df= 2239, p = 0.01], whereas uric acid was positively associated with CERAD total score [β (95% CI): 0.04 (0.00,0.08), t statistic = 2.03, df= 2233, p = 0.04]. The association between dietary intake of PUFA/ω -3/ω -6 and DSST performance was partially mediated by GGT level. Our findings support that PUFAs in dietary sources were associated with lower risks for cognitive impairment partially via lowering oxidative stress. Dietary PUFA supplementation may potentially reduce risk of cognitive impairment via antioxidative mechanism.

Liu D ，Zhou L ，Yang M ，McIntyre RS ，Cao B ... -  《-》

Association of Zinc, Iron, Copper, and Selenium Intakes with Low Cognitive Performance in Older Adults: A Cross-Sectional Study from National Health and Nutrition Examination Survey (NHANES).

Li S ，Sun W ，Zhang D 《-》

Threshold effects and interactive effects of total zinc and selenium intake on cognitive function in older adults.

The aim of this study was to assess threshold effects and interactive effects of total zinc and selenium intake on cognitive function in older adults. We used data from the National Health and Nutrition Examination Survey (NHANES) 2011-2014. Zinc and selenium intake were obtained through two 24-h dietary recalls. Cognitive performance was evaluated by the Digit Symbol Substitution Test (DSST). Smooth curve fitting, two-piecewise multivariable linear regression models, binary logistic regression model, multiplicative interactions model, and additive interactions model were used to evaluate the association between zinc, selenium intake and their interactive effect on cognitive function. A total of 2450 participants aged 60 years or older were included. Zinc and selenium intake was non-linearly associated with cognitive function. The inflection point for zinc intake was 8.94 mg/d in males and 7.58 mg/d in females. When zinc intake was below inflection point, zinc intake was positively associated with the DSST test in males (β = 1.02, 95% CI, 0.44 to 1.60) and females (β = 0.94, 95% CI, 0.26 to 1.62). When zinc intake above inflection point, there is no association between zinc intake and the DSST test in both sexs. The inflection point for selenium intake was 186.33 μg/d in males and 68.40 μg/d in females. Among males, the β (95% CIs) was 0.03 (0.01,0.06) to the left side of the inflection point and -0.06 (-0.10, -0.02) to the right of the inflection point. Among females, the β (95% CIs) was 0.13 (0.04,0.22) to the left side of the inflection point and 0.01 (-0.01,0.04) to the right of the inflection point. Besides, zinc and selenium have significant interaction on DSST test only in females (P = 0.028, RERI = 0.418). The present study demonstrated that zinc and selenium intake was non-linearly associated with cognitive function in different sex. There was an interactive effect between zinc and selenium intake on improving cognitive function, especially in females.

Wang X ，Wang H ，Zhang F ，Cui Y ，Zhang D ，Shen X ... -  《-》